Bài giảng: Những tiến bộ trong quản lý bệnh Glôcôm: Tối đa hóa tiềm năng của đo thị trường và chụp OCT

Đo thị trường (VF) và chụp cắt lớp võng mạc (OCT) là các công cụ không thể thiếu trong quản lý bệnh Glôcôm. Có nhiều chiến lược sử dụng hai công cụ này và những tiến bộ mới liên tục được giới thiệu. Webinar này sẽ đề cập đến các cách tiếp cận từ thời điểm lần đầu gặp bệnh nhân và theo dõi bệnh nhân theo thời gian. Webinar sẽ chỉ ra các số liệu quan trọng nhất cần theo dõi trên thực tế; đưa ra một số sai lầm/bài học phổ biến khi cán bộ y tế và bác sĩ nhãn khoa áp dụng công nghệ mới và thảo luận các ví dụ thực tế. Webinar này cũng sẽ dành nhiều thời gian cho phần hỏi đáp giữa người tham dự và các chuyên gia.

Điều hành Webinar:
Giáo sư Malik Y. Kahook, BS nhãn khoa, Đại học Colorado School of Medicine, USA

Giảng viên:
Bác sĩ Marta Pazos, BS nhãn khoa, Bệnh viện Clínic Barcelona, Tây Ban Nha
Tiến sĩ Danica J. Marrelli, BS Khúc xạ nhãn khoa, Đại học Houston College of Optometry, USA
Phiên dịch tiếng Việt:
Bác sỹ Hoàng Thanh Tùng, Bộ môn Mắt, Đại học Y Hà Nội


DR. KAHOOK: Good morning, everybody. I am broadcasting from Denver, Colorado. It is early morning. I just got my son ready for school. And guaranteed he’s gonna run behind me a couple of times here before we get started. Pretty excited about this session today. I’m gonna go ahead and share my screen so we can cover some of the basics of what we’re gonna be going over. Let me back up here. The session you saw in sign-up from advances on glaucoma management. This is a little bit different than discussions in the past where we got into the nitty gritty of the surgical maneuvers we might do or some of the disease processes that might be a little bit esoteric. The lest common things. Today is going back to the basics. Cover some of the basic points for visual field in OCT. Two of the primary ways that we diagnose and follow glaucoma in clinic with an emphasis on didn’t tools that you can use in clinic starting tomorrow morning. So, we want to give you all of the tools that will help you maximize the benefit of these devices. In order to do that, we have excellent speakers joining us today. This is my first time working with both of them on Cybersight. And I hope this is the first of many sessions where we can work together. We have Marrelli, clinical professor, assistant dean of clinical education, University of Houston college of optometry in Houston, Texas. And we have Marta Pazos who is calling from across The Atlantic of where Danica and I are sitting. consultant and head of the ophthalmic surgery section hospital clinic, Barcelona Spain. They will be doing the sessions and I will be moderating. We will have Dr. Marrelli cover Visual Field for 25 minutes or so, and Dr. Pazos will cover OCT for another 25 minutes. After that, we will have a Q&A session over about a half hour. If you want to add questions, we had plenty of questions that came in before the session started. We will go over many of those. And if you want to put in more in the Q&A box, we’ll also address those live as we’re going along. And then I might save some of those questions for the live Q&A between the three of us. Without further delay, I’ll hand this over to Dr. Marrelli, I’ll stop sharing if you want to share your slides we’ll get started.
DR. MARRELLI: Thank you so much for having me. It’s a pleasure to be here today. I’m going to share my screen and go ahead and get started here. I have a lot to talk about. And so, we’ll just go ahead. I’ll start with my — having a little bit of trouble here already. I’ll start with my disclosures here. A friend of mine recently said, we live in an OCT world. Not to steal Dr. Pazos’ thunder. I’m going to say that Visual Field remains an important test in the evaluation of glaucoma patients, glaucoma suspects on the diagnostic end and throughout the glaucoma continuum. This is one excerpt from the American ophthalmology’s preferred practice patterns. Visual field is critical whether you’re testing 30, 20 or 10 degrees, using white-on-white perimetry. Historically we did 30-2s. But the 24-2 test pattern test degrees superior and temporal. And it’s have early glaucoma mischief occurs. It’s ideal in glaucoma. And a little bit later on, I’ll talk about the value of the 10-2. I’m gonna start with kind of a template for interpretation. I teach optometry students. And I always teach them to go about things in a are a systemic way. The first thing to do, look at reliability. Is this a test that’s worth evaluate something then glance at our gray scale. But dig into our deviation plots, evaluate the global index measures and our glaucoma hemifield test. I’m looking for patterns of loss that are characteristic of glaucoma and I always want to try to correlate what I’m seeing structurally on my nerve evaluation, my nerve fiber evaluation, and my OCT with the Visual Field. Reliability is really important. We don’t want to spend time evaluating a test that’s not giving us good information. Our catch trials are located in the upper left corner of most visual field printouts and we have three catch trials. Fixation losses which historically 20% or higher is considered an unreliable test. But there are a lot of patients who have higher than 20% fixation losses. Maybe the instrument mis-plotted the blind spot or they have a very small optic nerve and you can still evaluate that field. I rely a lot on the technician to tell me if the patient was looking around. There’s another fixation metric we can use, that’s our gaze tracker. It starts at the beginning of the test, goes all the way through the end. When we see a mark that goes up, the patient looked away temporarily. A mark that goes down, that means the patient was caught during a blink. This is a helpful test for fixation. False negatives are a little bit tricky. They’re designed to evaluate whether a patient is really paying attention to the test or not. The problem with that false negatives is that patients with glaucoma visual field defects will have an increase in their false negatives just in the part of the visual field loss. In a field that’s relatively normal, high false negatives are an important metric for reliability. But in a patient with field loss, we don’t need to look at the false negative and rely on our technician. False positives are one that are really, really important. This is a patient that’s trigger happy. They’re pushing the button even when they don’t see a stimulus. When a stimulus hasn’t been presented. The problem with false positives, it’s gonna make the visual field look much better and high defects. False positives higher than 20% really are the marker of an unreliable test. The raw data, the threshold values, are not particularly useful in a single field analysis because the data is presented in other ways that’s much easier to understand. And like I said, we’re gonna glance at the grayscale which gives a set gray tone for a range of threshold values. But the grayscale is not intended to make diagnostic decisions. It’s intended to say, hey, in this particular field, it looks like we have a problem in the inferior part of the field. Where we want to pay attention is in our total and pattern deviation plots. They’re slightly different and I want to sort of remind you of the difference there is. The total deviation plot tells us at each point tests how far away from the expected value our patient is compared to age match normals. So, if we have a zero, that means no deviation, the patient is exactly where we expect. A positive number means the patient is more sensitive, and a negative value, the patient is less sensitive. I don’t pay too much attention to these numbers because I know when these numbers reach statistical significance, they’ll get flagged on the probability plot below. You’ll get one of the gray tones, darker tones meaning more statistically significant. In other words, a deeper defect. So, I typically look at the deviation project plot. What happens between the total deviation plot and the pattern deviation plot is really important. So, the easiest way to think about this is to think about a patient who has a cataract and has glaucoma. A cataract is gonna cause an overall depression in the visual field and the glaucoma is typically gonna cause a localized loss, a nasal step, a defect, something like that. If we have something causing a generalized loss, we won’t be able to see that localize the loss. The instrument filters out, if you will, that generalize the diffuse loss. What we see on our pattern deviation plot is kind of what remains. This allows us to highlight those local defects that are more characteristics of glaucoma. Now, in this particular example, my total deviation plot and my pattern deviation plot look exactly the same. What that tells us is that this patient doesn’t have any significant generalized loss. This is a 72-year-old patient. They’ve already had their cataract surgery. But here’s an example where you see a big difference between the total deviation plot which looks all dark, very depressed visual field, and the pattern deviation plot which shows us that this patient has a superior pericentral defect that would be consistent with glaucoma. In the first two fields, the patient had a significant cataract. In the last field, you can see that the total and pattern deviation plots look similar. That’s because the patient had their cataract removed. If I were gonna spend the most time on any one particular map, it would be on my pattern deviation probability plot. Our global index measures are underneath the grayscale over here. Those are single number deviations of the field. The mean deviation tells us on average how depressed this is related to normal. It’s not telling us there’s localized loss. It’s just gonna tell us an average of the deviation across the visual field. The pattern standard deviation, like to implies, is really gonna highlight local pattern-specific loss. This is kind of a measure of how smooth the shape of the hill of vision is. So, if there’s a big chunk taken out in a nasal step or an arcuate bundle defect, it’s going to highlight that by increasing in the number. The more recent of the global field measures is the visual field index. This is the easiest to understand because it’s an age-normalized percent of visual for the test. Zero, parametrically blind, patient can’t see any stimulus, to 100%, which is this patient’s vision is normal on this test. The glaucoma hemifield test capitalizes on an important finding in glaucoma visual field defects. If we think about the pattern of the retinal nerve fibers on the temporal side of the disk, they have this really ultimate respect for the temporal Raphe. They don’t pass over that horizontal midline nap means that glaucomatous visual field defects don’t cross the midline. We’re looking for asymmetry between the top and have the bottom of the field. The glaucoma hemifield test compares mirror image clusters of points above and below the horizontal midline and lets us know if there’s a significant difference in the superior and inferior field. There are a lot of different messages that the glaucoma hemifield can give us, but when it says outside normal limits, that’s a strong message there’s a big difference between the superior and inferior parts of the field. This is a really sensitive test at detecting that asymmetry top to bottom. But it’s not speck to glaucoma we can all think about different conditions that might result in an asymmetry between our superior and inferior field. If you will a detachment. Or a neuropathy. Or a branch retinal artery occlusion. Any of those could cause a difference above or below the horizontal midline. That’s gonna trigger a hemifield test. Even though it’s not glaucoma. The one thing I always think about and I try to teach my students when I’m teaching them about evaluating visual fields is to look for patterns consistent with the diagnosis of glaucoma. Sometimes we can get sort of distracted by things that aren’t really significant. And glaucoma tends to have three specific patterns of loss. Nasal step defects. Which simply means a different of sensitivity above versus below the midline in the hemifield. Paracentral, which represent these arced nerve fiber bundles. And paracentric on the bottom here and here, often seen in patients with normal tension glaucoma. I’m also looking for structure-function correlation. When I look at this optic nerve were I see an inferior notched rim. A diffuse loss of nerve fiber inferiorly. But I have a medium-sized local loss superiorly. When I look at this nerve, I expect and in fact I see a large dense superior arcate defect that is with the inferior layer loss and inferior notch. And I also see a smaller but not insignificant inferior as well. This is characteristic of glaucoma. This looks like a healthy knurl all around, until 5:00 on a localized notch. It’s on the OCT in the nerve fiber layer and in the macular ganglion cell scan. I predict this is a localized defect. I see a superior defect. Pretty consistent with normal tension glaucoma. And looking for pitfalls, where to go wrong with the visual fields. There are three things we can do wrong. One, evaluating a test that’s unreliable. There’s no point in doing that. Number two, not recognizing a visual field is actually an artifact, and number three, overlooking other visual field defects and calling everything a glaucomatous defect. This gives us information about high false positives. The trigger-happy patients. They’re clicking, clicking, clicking. And we can see 68% false positives. We’ll see very high supra human threshold value. No one has threshold values of 50 and yet here they are on the test. We’ll see white in our gray scale. These threshold values are so high that the instrument disrupt a gray tone for them. That’s a key finding there. When they have this total standard deviation swap, normally we expect the total deviation plot to look worse and the pattern to look better. When it’s reversed like this, the instrument, instead or ranges up the visual need to get an over-depression, it’s pushing the field down because of an overall artificial elevation. I always look at these things to know if I’m looking at a reliable test. There are a lot of artifacts. Probably a big artifact is mistakenly missing the fact that the patient has a learning curve. So, the first field might look worse, the next looks better and so on as the patient takes the test. We don’t want to put too much into the first visual field unless it really highly correlates with our structural findings. This is another common artifact. This occurs from the outer ring of the trial lens that’s put in front of the patient. More common with the high plus lens. But it can happen with any lens with the holder of the lens is not close enough to the eye. If it’s too far away from the eye. We’ll see this less with a 24-2. Typically on the nasal side. And that just means we need to go back and re-test and push that trial lens a little bit closer. This is a characteristic called clover field artifact. Three points, one in each quadrant and then fill in the other. If they are paying attention, maybe quickly lose attention, doze off or fall asleep, what you’ll end up with four points that look pretty normal in what looks like an overall depressed field. This is not necessarily depressed. We need to repeat it with better instructions and maybe a better-rested patient. Overlooking other causes of Visual Field loss goes back to trying to correlate it with the structural changes you will see. This is a patient who was sent to me because his screening Visual Field was abnormal. Whether you look at his Visual Field in isolation, it looks like he has a superior arcate bundle defect. This could absolutely by a glaucomatous visual fundus. But he has retinal scarring, an injury as a child. This visual field loss is due to retinal damage. We don’t to want ascribe it to glaucoma when he doesn’t have glaucoma. I said I would come back to the 10-2. If you asked me 15 years ago what do I think about 10-2s? I’d say I use them when my 24-2 shows advanced loss, but there’s still threshold values in the center of the field. when we look at the threshold views, the majority are less than zero. We are testing parts of the retina that will not respond to stimuli. But we don’t want to do visual field testing because this patient has some usable vision in the central 10 degrees. The large spots are the points on the 24-2 test. And the little tiny points are the points on a 10-2. All within the central 10 degrees. And instead of being 6 degrees apart, they’re more finely spaced at 2 degrees apart. I always think about this as kind of zooming in on a satellite map. So, we can really see the details in the very small area that we’re concerned with. So, when we take this patient, and we run them with a 10-2, we now have a lot more points that have registered threshold values that we can follow for change without spending a lot of time on that 24-2 testing points that aren’t going to give us any information. When you move to a 10-2, look at the rest of the field and ask yourself if you still need to continue doing a 24-2. In this case, if we go exclusively to a 10-2, we lose that arcate defect. Sometimes we have to go back and forth between a 10-2 and 24-2. The next question is whether there’s a role for the 10-2 in early glaucoma? This is coming from newer information that we know about early loss in the macula. A lot of this work comes from Don Hood at Columbia University. I want to draw your attention to the image on the right-hand side of your screen. Obviously we have a fundus image and on that, we have a macular layer, OCT, and then this red donut, this red ring in the center, this is where our ganglion cells are at their peak density. We know sometimes there’s early loss of these ganglion cells. But looking at the black square which is represent the points on a 24-2 field, in that area of densest ganglion cell, we’re testing for four points. We’re sort of under-sampling that area that may be damaged in early glaucoma. If we go back to our test points of 24-2 versus 10-2, you can see this square outline represents this area of the macular scan, the OCT scan. So, we can test much more finely in that central 10 degrees and maybe uncover some early visual field loss associated with early ganglion cell loss in the macula. So, this is a patient I like to talk about. He is a previous high myope. And previously — and now — oh, my gosh, are these glaucomatous or just disks? You don’t have the stereoscopic view, but I was concerned about the infratemporal rim in the left eye. When I looked at the 24-2s, nothing screamed glaucoma. Ah, these are first visual fields. Let’s look at what happened on the repeat testing. When I looked at OCT, I was struck by the loss of macular ganglion cells and went back to the field in the left eye, did discuss this one pericentral point superiorly, which I was willing to overlook, represent some visual field loss. I did the 10-2, and sure enough, there’s a sizable depression that corresponds very well to the ganglion cell in this case. I get the question, are you running 10-2s on all of your glaucoma suspects and early glaucoma patients. There’s difference between practitioners. Absolutely no. I run 24-2s as my standard glaucoma test. But a patient with a normal glaucoma 24-2 and see this ganglion cell loss in the macula, then run a 10-2 to see if I can find some visual field loss to correlate with that damage. There is a test pattern, called the 24-2C. The C stands for central. It is a standard 24-2 test with five additional test points in the central 10 degrees above the horizontal midline and 5 below the horizontal midline. Represented bit blue points there. This is in a way a little bit of a hybrid test between a 24-2 and a 10-2. Allowing us to sample a little bit more of those ganglion cells in the macula without having to run two separate tests. I have this test. I don’t use it frequently. It looks a little strange when the printout comes out because of these additional test points. I’m kind of getting used to it right now. I spent a lot of time talking about the single test point, right? The single field analysis. and what I want to talk about for the last few minutes is identifying progression in glaucomatous virtual fields. This is a much harder task than recognizing a Visual Field is abnormal. This is because of long-term test-to-test variable. We know that the more normal visual field will have some test-to-test variability, but it’s a pretty tight range. As our visual test gets worse, the amount of fluctuation from test-to-test increases. It can increase up to three or four times the amount of fluctuation we have in a normal Visual Field. If we had a patient, if we had perfect test-to-test repeatability, we follow this black line. When we have a test that looks worse than our baseline, we have to ask ourselves, is it worse but remaining within the expected amount of fluctuation or exceeded that test-to-test variability? We can look at an overview which has every visual field in a row. And in this particular example, it’s easy to say, yeah, this patient’s visual field has gotten much worse. They went have a small inferior nasal step to a large, dense inferior arcate and a new superior test. This is a lot harder. This patient had six visual fields and if we polled our audience, some people say it looks like it’s progressed. Some saying it looks like it’s stable, and a lot of us saying I’m not really sure. It can be very difficult. I’ve already said our grayscale is not really good for making decisions. We can look at our threshold values, but that’s time consuming and difficult to know how much change is real or significant change. We can look at our probability plots. But you can see there’s a lot of variability over time with those plots. And we can look at our main deviation and pattern standard deviation for change over time, but there’s a little bit of fluctuation in those values too. Probably about 2 decibels worth of variation from test-to-test. An important thing to think about when you’re trying to determine progression is how often should we do perimetry? How often should we do Visual Fields? We know from a lot of studies, but one in particular, that the changes are visual fields are most often not repeatable on repeat testing. And the World Glaucoma Association says we should repeat suspected visual field regression not one time, but two times to make that confirmation. Chauhan published a paper 15 years ago, saying six Visual Fields in two years. That’s not crazy, but being able to detect those patients who have rapid progression within the first two years. It’s going to take several Visual Fields to confirm it we’re confirming with two consecutive fielding. If we’re only doing one visual field test a year, it’s going to take 5 years to know if our patient is progressing. That’s really too long. A question that always comes up, is it practical to do six Visual Fields in two years? It’s not that hard. One test at baseline, a confirmatory test maybe within a couple of months. A test at 6 months, 12 months, 18 months and 24 months and you have your six Visual Fields. You will know one of three things. Your patient is one of those patients who is progressing rapidly and their treatment needs to be escalated. Your patient is stable and the treatment you’re administering is sufficient. Or your patient’s not a very good field taker and you may need to rely more on your OCT or your optic nerve evaluation to tell if the patient is changing. Other things may influence frequency of Visual Field testing, particularly if the Visual Field is impacting the central vision and if the patient has other risk factors for progression like repeated disk hemorrhages. I want to talk about the GPA, this is a progression software on the Humphrey Field Analyzer. But just due to time, I didn’t have the time to talk about the common perimeter that’s used around the world. I will tell you that they pretty much have the same types of analyses. They’re just called didn’t things. I’m talking about one instrument, but there are similar programs on other instruments. GPA is a software that was based on glaucoma patient’s re-test variability. And so, they kind of defined this test-to-test variability for us in real glaucoma patients. The GPA will tell us information in two different ways. Event analysis is what I call the yes/no question. Has today’s visual field gotten worse compared to the baseline? And that’s gonna be based on whether or not individual test points exceed the expected amount of test-to-test variability. If they do, we’ll get a little triangle. The first triangle is white. If the next test has the same amount of variability, the triangle will fill in halfway. If the third test, if that same exact point is still exceeding test-to-test variability will get a black triangle. If you have half-filled, possible progression. If you get a black triangle, you will get a message, likely progression. The other way the GPA shows us that vision is changing is trend analysis. With five reliable tests, this will give a slope of the rate of change Visual Field index. This will show the rate of change and hopefully identify those patients who are progressing at a rapid rate. This is what the GPA looks like. We have our two baseline fields, our trend analysis, and then we have our individual follow-up examples with our triangle analysis. So, on this particular example, we have, you know, a few points that have exceeded the expected test-to-test variability for the first time. And we have one point right here that last time exceeded the test-to-test variability and again today so this triangle fills in halfway. These are not enough to say that we’ve detected progression. We can look at the VFI trend line here. It will assume linear progression and show us not only what is the rate of change in percent per year, but also if things keep going the way they are right now, where will the patient be in five years? Some instruments and some data management systems have the capability to create a trend line of the main deviation instead of the Visual Field index. So, this is an example of forum, which is a data management system. In this case, we are trending — or we are watching the trend of the Visual Field index. If you look at this patient who has had a lot of Visual Fields over the course of 10 years. It tell us that the rate of progression is 2.4% of the Visual Field index per here. If you think about the dynamic range of the whole Visual Field and decibels being about 33 decibels and 100% of Visual Field index, one decibel is probably equal to 3% per year or 3% of the Visual Field index so, this patient is not progressing at a particularly high rate. But that’s not the whole story. If we look at the baseline Visual Fields here and we look at today’s virtual field, no one can deny that this patient has had pretty remarkable progression to really severe Visual Field loss. If you look closely, it looks like this patient was doing pretty well for a long time and then sort of has had some rapid progression. What you can do is go in and create a second time point that you create a baseline. And if we do that, we see that for 7 years this patient had a rate of essentially nothing. No progression at all. And over the past 3 years, they’re having a 10% change in their VFI per year. That’s more than a 3 decibel change per year which is really a dramatic rate of progression. This patient needs escalation of their therapy, especially given the fact that they’re only 72 years old and potentially have a long time to live. There are a lot of subtleties to this analysis. I wanted to put up a slide with resources. Excellent resources. I believe this book is available as a free download. You have to Google it and I believe you can get a download.S it an excellent book on the basics of perimetry. I will stop and go pack to Dr. Kahook.
DR. KAHOOK: Thank you. That was a lot of information in a short period of time. I think one important thing for the audience to remember is this will be posted in the next few hours. A little bit later tonight US time. So, that anybody can go to the Cybersight website, watch specific sections, go back and repeat. But everything in that talk was extremely valuable. So, I think it’s a great primer for nose starting to use Visual Field. Thank you.
DR. MARRELLI: Thank you.
DR. KAHOOK: And no going Oneisha to covering the same type of information for Visual Field, but for OCT. And keeps the questions coming. I’m trying to answer some as we go along. I’ll save some for the Q&A. But we will have about a half hour Q&A after this session is done with Marta. Marta, I’ll hand it off you and thank you for joining us.
DR. PAZOS: Thank you, Dr. Kahook, for the invitation. I’m very happy to be here today. And in the next minute, I’m going to try to give you some tips on how to optimize and taking the most out of your OCT. These are my disclosures. And as you all know, OCT is able to give us a lot of information about glaucoma and about deep glaucomatous neuropathy and gives us a global evaluation that goes basically into three different aspects which are the rim, the retinal nerve fiber layer, and the ganglion cell layer. What I suggest is that for the every day practice, that you’re systemic. And I always take into account these four points that I have written down here. The first of them is very, very important. And it’s assessing the quality of your — of your image. Of that test. And that — and the first thing you have to have in your mind is this GIGO effect, which means even if you’re a fantastic doctor, if garbage gets in, garbage will get out. So, it’s very important that you have a good quality image before interpreting if that particular patient has or not glaucoma. Which are the most important sources of error? There are two different things. Two different situations that I’m sure that you’ve heard which are the green disease and the red disease. The green disease is basically a false negative. So, the OCT looks normal. But actually this patient has some clinical evidence of having glaucoma. So, it means that it’s green. But the patient is sick. On the other hand, there is the red disease, which is a false positive. In which the OCT is abnormal, but actually the patient is healthy. And it’s very important, I will repeat this several times in the presentation, that OCT on its own is not able to provide a diagnosis of glaucoma. We have to do that together with a clinical examination. So, how can we do to know that our image is of good quality. There are basically two things. One is signal strength and the other is ruling out artifacts. For the signal strength, it’s important that you know your instrument. There are different instruments out in the market. And there is a number that basically you can look in the book of your instrument, in the manual. And under that amount of strength, under that amount of light, you should not take that image into account. And this is different, as I said, for each instrument. For example, for Cirrus service, is has to be six or more For Spectralis, 20 or more, Optovue, 6 or more. It depends on the instrument. It’s lower in patients with lower visual acuity and very affected by cataract and lower in myops. And you have to take all of these into account. Why is this important? If you have low signal strength then because the disease — then, because, sorry, the instrument will detect less light, automatically it will think that there’s more thinning. So, lower signal strength actually results in lower thickness which is not true thickness. And this is more important when as lower as this signal strength gets. So, for example, for signal strength, this is a study done in Cirrus, for signal strength between 3 or 6, it does have a mild impact. But for those that are really low, lower than 3, it has a substantial impact. And in glaucoma it has been shown that those changes in signal strength really. So, please, only take into account those images that have good signal strength for your particular instruments. The other aspect that we have to take in mind is the artifacts. Because they are much more frequent than we think. They can happen, it depends also on the different decease. But they can happen up to 15 to 46% of the images that you take. As much as almost half it could be. So, please check the segmentation. You can see sometimes decentrations, or movements like here. Also, pieces of the images that are gone. And look, for example, this image here in which basically this macular segmentation cannot be right. So, check segmentation because those things can have a dramatic impact on your measurements. In the retinal nerve fiber layer, the more common is to have decentration followed by the detachments. Look for that. And in macula, the more common is ERM. Taking that into account. And only evaluate these images that are good quality. I have some cases here for you it see. This is a patient that was referred because they were thinking that maybe it had glaucoma. Pressure was normal. And they are — this is an example of red disease. Because here you can see this unusual quadrant for glaucoma which is the nasal quadrant. But if you look at the segmentation, even more than that, you can see a posterior detachment that’s doing a shadow right here. And that’s why in this circle of measurement you get these artifacted thinning. You can also take a look into these graphs and when you see thinning that goes up to zero, this is never normal. We will talk in a little bit later about the flor affect. And basically in normal anatomy, the retinal nerve fiber layer never goes down to zero. So, if you see a zero somewhere, that means it’s very likely an artifact. This is another case. It may be a patient that we were seeing this patient for some time for ocular hypertension. And if we take a look in the ganglion cell layer, it may look like it’s worsening. It’s actually a paracentral damage that he or she is developing? No. In this case, if you look at the second patient, this patient had also diabetes. And what was happening here is that he or she was developing macular edema. So, you know, check the segmentation because in the macula, all the things can happen. And they will completely alter our ganglion cell layer measurements. And again, this is another example. This is a patient in which if we do this, look this low quality here for this particular instrument. And they show you here in red that the — that the quality is below what we want. And this is not well-centered. It is cut on top of here. And if you do take the image currently, then you have good quality and then this is not cut anymore. And basically, you get a completely normal patient. So, again, you know, quality is very important. Because it can make that had you diagnosis things that are not glaucoma. Or that you think that a patient with glaucoma is healthy. Now next step is diagnosis. So, going back to those different parameters that the OCT can measure, we will go first for the rim. The rim values like the size, the cupping, the nerve area — those give us a first idea in — at a first glance — of the optic disc appearance. They are useful to detect asymmetry and to have in mind the disc size and how this can affect. But they are not the most useful parameters of them all. Although some rim parameters, the minimum rim width which is a parameter available in a Spectralis show they’re available for the discs. They give some information, especially for defecting asymmetry. But the big thing still today is the retinal nerve fiber layer analysis. Still today it those been overcome by any other parameter when assessed individually. It changed before Visual Field damage course. It’s usual to detect early change and it just has a very good discriminate ability with areas under the curve of 0.9. It’s especially useful in early glaucoma, mild to moderate glaucoma, not so useful in advanced glaucoma. And the best parameters are the average thickness and the inferior thickness. Always have in mind that glaucoma typically happens temporal inferior. So, that’s why those parameters are typically the best ones. The second very important parameter that we use is the ganglion cell layer. It is very useful in early glaucoma, in suspects, to detect early change, paracentral changes. Focal damage that occurs. Especially in patients with normal tension glaucoma. And we have seen also very nice example of this with talk of Dr. Marrelli in which you can see these shapes that look like a donut almost that has a little area that has been bitten. This is called the Raphe sign, and it’s useful in funny discs that are difficult to assess. It’s help to feel look for these images. The most important parameters are the average and the minimum thickness parameter. But in the latest times there has also been a tend you to look at the deviation maps , I encourage you not to only look at the numbers. Because sometimes metrics in OCT can be difficult to assess. But also take a look at the segmentation and at the deviation maps. Sometimes when you just look at sectors of global indices, you can musculoskeletal some glaucomatous damage. And this is likely a glaucomatous damage. And when see say the Raphe sign or snail shell appearance, think this patient very likely has a glaucomatous neuropathy. This is in patients with myopia in which sometimes those parameters are difficult to assess. But in the latest years there have been now some studies showing that it’s very important to combine parameters. And actually if we are able to combine things, we get best results. So, we don’t need to use one or the other. But use one and the other. And I have some examples for you about that. For example, this is a patient that has mild myope. He has a slightly tilted disk. We fill this 24-2 field in which there are like in Dr. Marrelli’s example some, you know, very early points, maybe first field. We’re not very sure if this is glaucoma or not. This is the rim, as I said, this temporal inferior damage. This is the retinal nerve fiber layer thickness in which this is borderline area. We’re not sure. Look here, again, this temporal inferior area of the graphs. This is very likely glaucoma. But if we do a macular OCT, we see this Raphe sign, this snail shell appearance. Which confirms that very likely this patients has glaucoma. This is another case. You actually don’t need an OCT to know this patient has glaucoma. Just by the clinical examination you see these very pretty wedge defects in the retinography. if you look at the OCT, it’s green. This is example of green disease. But looking more deeply, you will see here in more detail where the defects in the deviation map. You can see some asymmetry. I say always this to my residents, it looks and smells of glaucoma when you see asymmetry. And when you the — sorry. If you do — for some reason it is not — let me maybe… here is the good one. Sorry about that. Yeah. For some reason this animation is not working. But I’m showing you right here. So, if you do the macula, you see this snail shell appearance. And inwith this normal OCT, look that the visual defect is already there with some paracentral damage. With fixation that’s already affected. So, it’s not as field damage as it looked like only with the OCT. Now it’s working. Well. Let’s go now for structure and function relationship. Because this I think is very helpful. When things match, when the structure matches function, that’s something that helps us to be more sure that this patient has glaucoma. First, I want to let you know that structure and function relationship depends on glaucoma severity. So, in early glaucoma, in which we have more thickness then visual field doesn’t change that early. Structure change early in time. So, OCT is more valuable than Visual Field in early glaucoma. At the end of the spectrum in advanced glaucoma, then OCT reaches what we call the floor effect. So, it can not go lower. It’s a question of a dynamic range of the instrument. So, it can not measure any more. At that point, there is still some way to go for the Visual Field. So, in advanced glaucoma, Visual Field gives more information than OCT. And there’s this intermediate situation in, you know, establish moderate glaucoma in which structural function are more correlated. So, it’s important that you have that into account when you look for structure-function relationship. Also, and Dr. Marrelli has also commented very nicely that 24-2 SAP sometimes does not study well central damage. Because only four tests fall within the central eight degrees of vision. That’s why you have to look at macula. And OCT sometimes is an easy way to do that. I have an example. This is a 55-year-old female with a normal tension glaucoma. Look how this notch is right here. Temporal inferior. If we take a look at the field, we may think it’s not that much. But look here. How the retinal nerve fiber layer is affected. And also, these defects of the ganglion cell layer. And if we then do a 10-2, as Dr. Marrelli suggested, you will see this is much more than we thought. And basically this alteration is affecting fixation. So, it’s good to take a look at the macula. OCT macular OCT can help us to further assess function because of the structure relationship with it. And it’s an easy, if I can way to take a look at the macula. Last for progression. It’s important to evaluate structure over time. Bearing in mind that still today the gold standard for detecting progression is Visual Field testing. But structure can give us some tools to complement our detection of progression. My advice is use trend analysis. It’s more intuitive and simple. And it’s able to detect most eyes with clinically significant progression. And it’s been shown to be the most important parameter to start treatment. It’s important as it happens in the Visual Field testing to have enough tests. At least five tests in two years. Because that’s the way that the device can give you a reliable rate of structural progression. We can assess them over time with the same parameters. My suggestion is to use retinal nerve fiber layer and ganglion cell layer. Again, retinal nerve fiber layer is the most-used because it has high sensitive.. And it’s very useful in early glaucoma. But because of the floor effect, not so much in advanced glaucoma. It’s important to know that there’s a variability to the instrument. So, just because of the instrument, if we do several tests, we can have up to five disenfranchisement from one test to another test done the same day for the global average. So, everything that’s between these 5 microns is just variability of the testing. It’s something we have to have into account. The other thing we have to have into account is because of aging, there’s decrease in retinal nerve fiber layer that’s up to 5 microns in 10 years. That’s how I remember. 5 microns of variability, 5 microns of change in 10 years related to aging. Why do I say that? Because these instruments are not correlated by age. And if we age, we will lose retinal nerve fiber layer. Some studies have been done to see that. So, be careful with significant slopes. Because we only take a look at that. We can have high false positives. And what we think because of several studies is that if you just wait enough, if you only look at these statistically significance of the slope, everybody will progress if you wait enough time. So, you have to go to the 5% limit of this normality. And that’s about 1 micron per year. So, if you see a loss that exceeds that micron per year, very likely this is clinically significant. And again, I have some examples for that. So, for example, this is a patient that has a pretty stable visual field. It’s a very early glaucoma. Look here. They — there are some points, but the field looks about normal. But if we take a look to the retinal nerve fiber layer over time. We see that actually there’s some laws over there. basically more than 3 microns per here which when we take a look at the event analysis, which is the more focal change, we can see something is happening here inferiorly. Now with time, the visual field is also showing some changes superiorly. So, probably here, only with the changes that with this amount of change in the OCT, we would enabled that this patient was progressing. How about the ganglion cell layer. So, it has less sensitivity than the retinal nerve fiber layer. But it’s better than the nerve fiber layer to detect changes in advanced glaucoma. It has little bit more of a range. This floor effect — sorry — occurs later in time. So, for the variability of the macula, the significant amount of change is 4. And again, there’s some decrease with time, with aging, that is a little bit less in the macula and is about 0.32 microns per here. And in the — in cases like this patient that has an advanced glaucoma, all the superior field is gone. It looks more or less stable. The 24-2. If we take a look at the OCT retinal nerve fiber layer, it’s stable over time. Why? Because we are in the floor effect. But if we look at the macula, there are some changes here that are exceeding this micron. And some focal changes, paracentral changes, occurring in the ganglion cell layer that basically probably our 24-2 is not capable to detect. This patient is probably progressing centrally. There’s some evidence that combining parameters is useful. Sometimes for your patient macular will be better. Sometimes for your patient, retinal nerve fiber will be better. So, the nicest thing is to detect in combination and also use deviation maps which are sometimes useful. Like in this patient in which you can see how this structure and function in the structure of both parameters at the same time we can see that this was getting deeper before actually the defect in the visual field appearance. Sometimes having all the picture in your head is very helpful to see what’s happening. And now in conclusion, the take home messages that I would like you to have is that — sorry. Because this is the wrong — sorry. Sorry for that. Because this was not the — the area. Sorry. So, the take-home messages now is the correct one that I wanted to have is that quality is extremely important. That yo need to check signal strength, rule out artifacts that combining all available parameters is the best way to evaluate structure. That structure and function depends on the severity that OCT is better in early glaucoma. Not so much in advanced glaucoma in which you have a floor effect. That macular damage is much more frequent that we think and that it’s under-represented in the most used 24-2 field. But it’s important not to evaluate only statistically significant change, but clinically significant change in terms of progression. Take into account that slopes are not corrected by age. So, you have to exceed that normal effect of aging. And on top of this, please remember that OCT results do not provide diagnosis on their own. So, you have to evaluate all these together with the clinical examination. And that’s all that I wanted to say. Thank you very much for your attention.
DR. KAHOOK: That’s great. So, again, a lot of information. And there are some questions that came in about the wealth of information that was shared in both of these talks which was totally expected. And one of the reasons why these sessions are recorded so you can go back and play and re-play — I’m still playing and replaying the basic lectures I had 20 years ago in residency. Some of the questions that came up in the Q&A I had to look up just now. Some of the basic stuff that we just — we don’t think of. A lot of us went through some of the basic training with, you know, other medical techniques. So, one of the corollaries that I think of is when you’re looking at an EKG, and you’re trying to figure out heart pattern. You get so good at it, you look, this patient is fine or this patient is having a heart attack, right? It’s the same thing for a Visual Field. Marta said this, that it smells like glaucoma. If you’re looking at a nerve, even if it’s not one nerve and comparing the difference between the two sides, sometimes you can tell. Even without a notch. There is something about the nerve that’s saying, look. Look more closely. That’s part of the art of what we do with eye care, right, so I have a bunch of questions that I have listed. I’m gonna try and go through as many as possible. But I would encourage the audience to continue to put questions into the Q&A. I’ve answered about 35 or so of the questions that came through. So, and then when it got to things that I wanted to discuss live, I left it for this part of the discussion. So, thank you again to both of you. Really great talks and I’ll go back and myself I’ll listen to this and my residents I know will go in and take a look as well. I’m going to start off with a very unfair question to both of you.
DR. KAHOOK: That’s a great way to start it, yeah?
DR. PAZOS: Yeah.
DR. KAHOOK: So, there were some questions that came in from a couple of different audience members this is great if you have access to Visual Field and OCT, but if you’re in a resource-limited area, What would you do? Start with Danica, if you were going it a low resource area and doing clinical care how would you approach glaucoma in those areas?
DR. MARRELLI: It is a bit of an unfair question. But I served on a panel one time, if you were on a deserted island and you could have one instrument, what would it be? I’m gonna ask for two, a slit lamp with a tonometer and a 78 diameter lens. No matter how we talk about official fields and okay, the first shot is to look at the optic nerve and look for the characteristic changes. The other things are supplementary. I recognize resources are different. I work in an urban clinic in Houston, Texas. And I have some patients that have lots of resources and I personally have lots of resources in my clinic. But some patients don’t have insurance or they can’t afford the care. And so, there’s no doubt that we have to modify what we’re doing for the given situation. But I think that we will never be able to throw away our interpretation of the optic nerve.
DR. KAHOOK: Yeah, totally agree. Marta, what do you think?
DR. PAZOS: I totally agree with Danica. I try to teach to my residents, this is the glaucoma neuropathy, look at the optic nerve. Being a heart doctor and not listening to the heart. This is the first thing and nothing is going to substitute this. As Danica said, these are complementary tools that are very helpful. Especially for tricky cases which are not the rule can help. But if I only had to have one thing, it would be to looking at the nerve. For sure.
DR. KAHOOK: I’m gonna agree with both of you. I think most clinical practices, clinicians who are trained in doing eye exams have access to some sort of tool to look at the optic nerve. And even those tools can be very expensive depending on where you are. But I think that’s sort of the bare necessity of diagnosis and following. Being able to access the optic nerve, whether it’s direct or indirect. In the future, it would be really nice to have access to less expensive tools that leverage artificial intelligence that can then look at the optic nerve and then tie in what the system might have learned from looking at visual field and OCT along with that optic nerve. So, you know, my dream and one thing we’re working on here at the University is to be able to get a system with an algorithm that is so trained that you can look at the optic nerve and predict the OCT and predict the visual field just by looking at that. And that can be done with minimal expense once the system is trained. So, I’ll also say this that Cybersight has an AI tool where clinicians from all over the world — depending on some of the regulatory aspects, of course, that play into it — can upload photos of the optic nerve or the retina and you can get expert opinion as well through some of the clinicians that work with Cybersight. So, that’s another tool that I’ll throw out there if you don’t have access to all the fancy diagnostics that question use. Speaking of fancy diagnostics, one thing that came up briefly is 24-2C from a Visual Field standpoint. We had a few questions on that. I’ll start off by saying that in our clinic we have 11 glaucoma clinicians along, you know, with our adjunct faculty. Everybody will do things slightly differently, right? But 24-2C is one of the things that caught on with all of us. And we are using it a great deal with our patients. So, I’m wondering what the two of you do. I’ll start with Danica after the Visual Field lecture. How you using 24-2C and what recommendations do you have for that?
DR. MARRELLI: I would say I’m early in my learning curve. We had four units that didn’t have that capability. Now replaces one, now replaced a second. Depending on where the patient has their visual field run, I may not be able to get it. I’m still learning how to look at it. It looks skewed, like the paper was stuck in the printer. I think it’s a valuable tool. I think we struggle a little bit, trying to decide whether to do a 24-2 or a 10-2. I was at a meeting where I don’t remember who said it, they said a 10-2 is a missed opportunity at a 24-2. You’re hedging your bets when you run one or the other. This kind of almost hybrid, not exactly, but kind of hybrid is really nice because I do see those macular changes on OCT frequently and I think you may be able to pick them up a little bit earlier. My goal is to adopt it a little bit more frequently now that I have two instruments that do it.
DR. KAHOOK: Marta, what do you think? Do you have access to 24-2C?
DR. PAZOS: Yeah, we have it. I’m a little bit like you. We’re using it more and more, you know? I think that’s a good in those patients in which you really think that you may find — even before the ganglion cell layer is affected. If you have a patient with normal tension glaucoma, I would clearly go for that. If I see a point, then maybe study further with a 10-2. But that’s very helpful. Because you really catch, easily, some, you know, paracentral early damage that how you would have missed and you don’t need to do one test and then outer test. We sometimes — we do this more and more, even for screening.
DR. KAHOOK: Yeah. Same here. One of the questions that came through that I thought was a really good question about 24-2 being perhaps too fast. Will patients get overwhelmed with the speed? I had that worry initially. There are some patients who cannot handle a 24-2C. In which case we take them back to 24-2 and those patients do fine. There is flipside to that, 24-2 might be too slow and fatiguing for many of the patients. And the faster algorithm, while it might miss on some levels will actually allow patients to be more alert during testing and the quality of the information that you’re getting will be good. Now, there are some subtleties that probably go beyond this discussion about making sure you don’t tie in the FI or the progression of 24-2C directly with 24-2. A 10-2 is going to give a ton of information from a standpoint that 24-2C won’t give you. But it’s telling that the entire faculty switched over to 24-2C and the other tests are the exception now. It’s a really important point. Not everybody has access. But I think it will increase as people renew their machines, you will get more and more of it.
DR. MARRELLI: The faster algorithm is the only way of 24-2C is available is faster. And those patients with seated standard or fast tests, I have a little worry when you transition them. I think if you tell them, look, this test goes faster. You need to be really alert when you’re doing it. I think most of my patients have been able to handle that transition. I do tell them — if they haven’t done Visual Fields before, but if they have, this is designed to go much faster. You have to eat your Wheaties and be ready to go on this one.
DR. KAHOOK: Yeah, I prescribe coffee before my 24-2 —
DR. PAZOS: I was going to say, they have to be awake.
DR. KAHOOK: I love it when my patients came in and said, sorry, Dr. Kahook, I fell asleep during this test. Yeah, I can tell.
DR. MARRELLI: I didn’t know!
DR. PAZOS: On the other hand, it’s a lot faster. Some patients think it’s a long time to do the test. It’s also good for those patients.
DR. KAHOOK: And just a general comment for everybody listening in that’s seeing patients, once every couple of years take a Visual Field test. Don’t take the 24-2C and have your patients use it unless you take it yourself so you can see the differences because then you can communicate it much better. When we have residents and fellows rotating, we actually ask them to go ahead and do the test so that they can get an idea. One of the subtleties with Visual Field in glaucoma is patients with poor vision who are coming in and have a baseline poor visual acuity. What things, Marta, what do you do that’s different for a patient who might come in who needs Visual Field testing who has pretty poor vision, including compromised central vision? Would you still do Visual Field? What’s your thought on that?
DR. PAZOS: I mean, we do have a very good optometrist team which are trained for those situations. I really like to try to have a Visual Field test. Because this is the only functional tool they really have. So, I will do whatever. At least to try it as much as I possibly can. Also, as I said, Visual Field is the gold standard for assessing progression. It’s really the way that you’re 100% sure that patient is progressing. I wouldn’t like to miss that opportunity. Having said that, I sometimes increase the size stimulus. That helps for those patients. Sometimes we change. You know, they — and you really have to be with them all the test. You know? You always have to be with them all the tests. But in these patients, even more. Particularly. Even show them that they can stop the test if they are feeling stressed or something. those would be my ways of doing this. But you need to work together with your optometrist team so make sure you’re on the same page.
DR. KAHOOK: Yeah, Danica, what do you think?
DR. MARRELLI: Switch to the low target if you’re getting the false negatives. A pearl I learned a long time ago, if your patient can count fingers, they’ll be able to see a size five target. If they can’t count your fingers, they won’t get an automated test done. If they can count fingers, and they have low acuity account, they can do a size five. There’s better repeatability with a size 5 than a size 3. You lose your ability to do progression software, you can still follow a size 5 Visual Field over time for a change. It just requires — it’s a little bit more cumbersome to detect that change.
DR. KAHOOK: those are great pointers. We don’t talk kinetic and static testing. We don’t run one as much as we used to. It depends on a technician that’s very good. But the interaction between the person administering the test and the patient can bring South findings that you’re not going to get from the static testing that we’re more accustomed to. That’s another thing I throw out. It doesn’t always help. But in certain patients, doing from static to kinetic. A lot of my patients have never taken the kinetic test. See for you get something out of that would be good. A scenario that came up in a few of the questions, what if you have disagreement, what there there was disagreement between the Visual Field and the OCT. When you’re seeing a patient, you have the optic nerve exam, potentially photo, OCT and Visual Field. What do you do when you have disagreement between them? Who wins? How do you think of that?
DR. PAZOS: Again, as I said, the structure-function relationship. This agrees over the spectrum of the neuropathy. So, it’s not — it’s gonna be very likely there’s gonna be some disagreement. You need to understand first in which area of this spectrum you’re situated. So, early in time, opacity structure will win. Of course, for — as we said with Danica, examination is the first, right? But recording structure and function early in time structure will win. Probably later in time, function will win. And if there’s disagreement in the middle situation, then for me, my clinical examination, the interocular pressure, all the clinical things will also be very important.
DR. KAHOOK: Yeah, I agree with all of those. Danica, what do you think?
DR. MARRELLI: Yeah, I think when we don’t have agreement — so, I think there’s a difference in disagreement and lack of agreement. So, if we have, you know, oh, this is a little visual field defect, I might have predictive that it would be bigger. I don’t think that’s necessarily disagreement. It’s not disagreement, it’s lack of agreement. If I have one that says this superior nerve fiber layer is bad and I have a superior visual field, that’s disagreement, right? That’s really different. And then you kind of have to say, one of these tests isn’t right. Something — there’s an artifact, you know, something’s not right. I tell my students, glaucoma is not always easy, but it always makes sense. You’re never gonna have superior nerve fiber loss that correlates with the superior field defect. That’s not how the eye works. Make sure that your not looking at artifactual information. Saying is this really glaucoma? Is this something else that’s going on and not glaucoma? So, I think there’s some subtleties there. But I agree that the clinical exam is gonna win every time. And sometimes too those a are the cases that you wait and see what happens, right? Is there a change? Is it repeatable? You know, instead making decisions on one day in one set of testing.
DR. KAHOOK: Yeah. I say that to my fellows frequently. That one of the main reasons I went into glaucoma is you can always have the patient come back for testing.
DR. PAZOS: That’s so true.
DR. MARRELLI: Step down from the ledge, right? Step down from the ledge. You don’t have to jump today. We can take a step back and say, is this urgent? No. Okay. See what happens next time the patient comes in.
DR. KAHOOK: Yeah, an example of that was recently a couple of weeks ago we had a patient come in and the testing didn’t make sense at all. I went and put in artificial tears in, walked the patient over again and had the fellow come in and say it looks totally different. We can be aware that the testing can have disagreement. I like what you said, lack of agreement. The way that you think about it, it can be influenced by so many different things. One question that came up, a couple of them, actually, were directed more towards octopus than Humphrey Visual Field. I personally don’t use octopus testing. I read about it but don’t use it daily. I’ll start off with Danica, do you use octopus testing at all? How do you think about it? If somebody is asking you about it.
DR. MARRELLI: I don’t have it or use it. I have done a lot of reading. I feel like I’m giving a one-sided view of things. The octopus perimeter is a great perimeter. It has a lot of great test patterns. You can go in and do a customized test pattern. If your patient had a superior nasal step, you can increase or decrease the spacing in that particular area. There are a lot of customized things you can do. And again, they have analogous software for pretty much everything that the Humphrey Field Analyzer has. I don’t use it. I think one of the things that’s always tricky is: Can I interchange them? And I really don’t think you can. I was thinking about an analogy. I don’t know if this will ring true or not. I like to run. And I have Nike shoes and I have Adidas shoes, right? And I can run with either one. But I’m not gonna run with one on each foot, right? And so, I think what you start with is the one that you stay with. I don’t think — I think you can get into trouble trying to compare them. Although you’re gonna see similar things. If you took a single field of open, they’re similar things. I don’t think you can use them to watch for progression. I think it’s gonna be comparable.
DR. KAHOOK: Yeah, I agree. Marta, what do you think?
DR. PAZOS: We don’t use it either. I completely agree with Danica. And I think actually the octopus is a very good primer. That’s what I know, that’s what I’ve read. I think it’s important to do the point that if you have an octopus, you’re good. You just have to stick to your parameter. It’s not that you need to change now. But I don’t have enough experience with it.
DR. KAHOOK: You would say the same thing about OCT as well. We covered both topics, Cirrus, Spectralis, whatever you have done, if you’re sticking with the same machine. You can’t put an Adidas on one feet and a Nike on the other.
DR. PAZOS: They are not interchangeable at all.
DR. KAHOOK: If you have a machine and you’re using it, it should be fine.
DR. MARRELLI: And learn whatever you can about your instrument. Love the one you’re with. I’m not gonna tout one instrument is better than the other. But whatever you have learned everything about it. What are the subtleties? What are the pitfalls and the benefits of the instrument you have or are considering purchase something they’re all good instruments, you have to figure out how to use the one you have.
DR. PAZOS: Exactly. You need to know your quality. You need to know how you’re measuring things. They’re not exactly the same. Some parameters for the macula, some measure the three layers, some of them measure only one layer. Some of them measure — you just need to understand and then to specifically know how to look at your device. How does your device check for progression? It’s fine, just use your device. And as you said, take out the most of your particular device.
DR. KAHOOK: Yeah. I think one big challenge for industry. It’s always a tough discussion to have. But the cost of the machines. If there’s a way to have sort of like we do for cataract machines where we have maybe a simpler grade that can travel with the surgeon and then there are more complicated machines. If we can have more complicated Visual Field and OCT testing capability, that’s a big challenge. I know some companies are trying to address that. It would be good to see to more clinics have access and can build a database around these machines. One question that came up, we can show age by recognition of the terms. GDX is not something that’s talked about anymore. HRT. I was in training during the GDX/HRT/OCT war, right?
DR. PAZOS: I was resident at that point. So, I was there. Yeah, yeah.
DR. KAHOOK: Right. And I did my fellowship with Joel Schuman, one of the inventors of OCT. But we do all three tests on each patient. It was part of his research. But first moved to Colorado, I was determined to get an HRT, had it and used it with OCT. And woke up one day, HRT was no longer on the software standpoint. If people have access to the machine which is I don’t think are being serviced. At least I think the GDX is completely offline, did we lose anything by losing GDX and HRT? Or is it progress and we have OCT now and it’s doing just fine. I’ll start off with Marta on this one after the OCT talk. How do you think of those two things? HRT and GDX.
DR. PAZOS: GDX I think is out. And I don’t think we have lost a lot. Basically what it did — it was measuring thickness indirectly. Because actually it was like a by reference thing. It was not true thickness. It was — yeah. An idea of a function. But, you know, it turned out that it was not as much as it had to be. So, GDX, it’s fine. I was worried a little bit at the beginning with HRT. Because actually I liked the progression analysis. I think the progression analysis by HRT was very good.
DR. PAZOS: I was — I did my fellowship with Jack, an HRT man. As you know.
DR. PAZOS: And at the beginning, some of my patients when we had the two that I had a lot of information for a long time with HRT, I was still doing some HRT to them. I think that now currently all these, you know, changes and evolutions I mean, the OCT now is much better than the OCT then. Inning we have these pseudo-histology images that you can see. Soon we will see with the optics maybe little ganglion cell. I’m sure now OCT is better. But at some point HRT was very good. If there’s somebody out there following a patient with HRT, I think that the important is your analysis over time. So, this information is of some value. At least for me.
DR. MARRELLI: I think the biggest thing we lost was all that time that we had. All of those exams we had.
DR. PAZOS: Those are gone.
DR. MARRELLI: That didn’t transfer to any other instrument. I think the companies have gotten better about having newer instruments be backward compatible. Because, you know, I think at the end of the day what we’re looking at, has this changed? Is it changing at a rate that’s alarming to me? Do I need to amplify my therapy. I really liked the GDX. And then went strictly to OCT, and went strictly to OCT. I have years of information on this patient on GDX. I don’t have that anymore. I think the main thing we lost was those individual patients’ back data. You know, it’s just one of those things. Well, I don’t have it. And I have to start from scratch.
DR. KAHOOK: Yeah, sometimes we just have to do that. Sort of dovetailing into that is the new transition that’s happening on a slow scale, slow, smaller scale, is the VR headsets. And we’re seeing a lot of companies — a couple of them have actually come and gone. It’s really a tough field to be in. And it’s mostly been centered on visual field testing. But there are goggles now that are being introduce odd an very early level that can do OCT or table top sets that can be taken to the home or rented out. What do either both of you — I would like to hear from both of you — how do you think of VR Visual Field testing and how that might play into your clinical practice and start with Danica.
DR. MARRELLI: I have not used one. I don’t have one available to me. I have sat in on some seminars, some sort of consulting advisory board panels with a couple of different instruments. And I think that there’s a lot of appeal, right? It’s small. You don’t have to go into a dark room. You can do it in any place, it’s fast. Patients accept it really well. At this point, I don’t think we have enough good data that we’re gonna be able to follow glaucoma patients over time. I think it would probably be good for a screening. Might even can get a threshold test. Although I think the dynamic range is not as large as with a traditional Visual Field unit. I can imagine that in a place where you’re trying to quickly identify, you need something that’s quick. You need something that’s maybe inexpensive. I can see the appeal of it. But I don’t think it’s quite ready for prime time in terms of managing glaucoma patients over the long time. I would like — I’m intrigued by it, but I just don’t think we’re there yet. And I think that the fact that we have seen companies come and go is a little bit much an indication of that right now.
DR. KAHOOK: Yeah, what do you think, Marta?
DR. PAZOS: I have not used VR sets. But I have seen goggles that do Visual Field for a long time. Not a lot of patients, but some patients. And also with tablets which was the previous — the previous software. And as Danica said, there’s a lot of appeal. In general for home monitoring, you know? So, that’s also good that the patient is there. But there’s not enough data. And I’m also worried about these — the repeatability. You know, there are some things, the fixation. How you make sure that there’s no movement. All these kind of things that I think there’s — we need more data, more time. And I don’t have experience with — with the virtual reality ones. Maybe you can tell us your experience with that, Malik. But those are the future. I suppose.
DR. KAHOOK: Yeah. I think it is the future for certain patients. And I think it’s sort of to be determined if it can replace Humphrey or Octopus that we’re using more frequently. We are using a system. I personally looked at several systems at the floor at Academy and other meetings. I’ve done it myself. We have one system that we brought into the clinic that we have been using. And patients love it when they’re using it. It goes back to the conversation of you cannot take the visual field data from the goggles, from the, you know, VR headset and apply it to Humphrey or Octopus. Progression analysis is almost nonexistent. But patients who have physical limitations, whether can’t sit at the Humphrey or Octopus, I think that’s a really good place for it. I think in the future, most practices that are tertiary care centers what might see the more difficult patient to take care of, you almost need to have this thing sitting there to take care of patients. The other thing that I think is gonna start happening is you’ll start seeing some of the companies sort of go by the wayside and you’ll start seeing the other — the survivors sort of build up and getting the normative database. And the other place where I think this is gonna shine is in screening. So, if you’re taking this out into low resourced areas, if you’re in the middle of nowhere and you have a couple of goggles, I think it will be very effective in screening patients. So, for the sake of time, I’m gonna do a couple of questions that I think might be more rapid fire. One of them is about normative databases. So, if you’re looking at OCT in kids, for example, where we don’t have a pediatric normative database, Marta, how do you think about seeing — let’s say the patient is 12. Maybe got diagnosed with ocular hypertension probably because they were squeezing during the test. How do you look at them for OCT and use of OCT if n that patient population?
DR. KAHOOK: Well, what I do it, again, this clinical examination is important. As we said. But then I use them to compare with themselves rather than to have a database because there’s no database over there. You have to think and you will know. But I didn’t mention this in the talk. Bull amazed that most of the database are not that many patients. Even for the patients in which you have the age. Some OCTs, the database was built in 300 patients, maybe.
DR. PAZOS: It’s not that much. Even with our patients, our normal patients, maybe the database is not there for the particular patient, with the characteristics of this patient. I compare the patient with himself, with herself over time. Which is all I can do.
DR. KAHOOK: Yeah, Danica.
DR. MARRELLI: The other key thing I think about it, I don’t remember learning this. I’m older than both of y’all. But I don’t remember learning this when I learned about glaucoma. But asymmetry is so key. And every instrument has the T-stint or curve superimposed right eye over left eye. We don’t have normative database, but we can look at asymmetry. It’s hallmark in glaucoma. Top-bottom in your nerve, in your field, in your OCT. That would be one other thing that you could look at. I think it’s worth getting because you will be able to track changes over time. But, you know, you just know what your limitation is when you’re using it.
DR. KAHOOK: Yeah. I think it goes back to one of the gifts for glaucoma is that we have time and longitudinal data will always be king in what we do. You can do that for a Pediatric patient. Some of the other questions coming in were about tilted nerve. In highly myopic nerve, change over time. Following the progression in a glaucomatous pattern. And there was a question about shifted bundles and what does that mean? You can have a shifted bundle that doesn’t follow the T-snip rule and looking at that over time will give you some insight. There are a lot of pearls here about not just looking at one test and making a determination. Sometimes the patients come in, never a notch, they have a nerve fiber hemorrhage and their pressure is 28. It’s basically a gimme and you know what’s going on. But more often than not, patients are coming in and you’re seeing their baseline and say come back in a couple months and take a look. I’m going to close off with more of a comment that’s more important from a friend of Orbis, some of you can see her question in the Q&A section. She is on the retina side of things, but taking time to listen to some glaucoma discussions which I’m appreciative of. We talk about representation data in AI, but not necessarily in OCT. How representative is the normative data target with based interpretations in these gadgets? In Visual Field and OCT? Which is exactly what you just touched on. So, this is a big problem that we need to address. And, you know, I’m getting sort of on my soapbox to talk about this. We talk about getting less expensive devices like Visual Field and OCT in low and middle income countries. But we can’t forget about representative data. We can go with intraocular patient. The range is based on very few patients who were mostly Caucasian. It’s not a wide range of patients. Take the OCT and go into Sub-Saharan Africa, the normative database is not represent that have data. The — fix is longitudinal data. I will keep saying that. Don’t go by one test. Follow over time. Our time is up here, it’s already the half hour point. We have gone for about an hour and a half and we have learned a ton. I thought both of your talks were amazing. I’m gonna go back and listen to both when it’s up on Cybersight in a few hours. To the speakers, thank you. Hopefully I can do another session. I compare to what I’m doing, wearing a Nike on one to do, Adidas on the other. I will use that and not attribute it to you. I will say it came off the top of my head. And Marta, you have been busy and traveling too. Thank you for making time in your busy day and giving an excellent talk that I thought covered a lot of the basics. To all of those who are listening in on Zoom, please go to Cybersight not just for this talk, but for many others. The library that’s in there, all of the courses that you can take. We have textbooks in PDF format that you can download and use for free. So, please enjoy that. Write in any questions also on Cybersight and we can get to some of those. I look forward to my next webinar. My next webinar is planned for March of 2024. And we’ll advertise what that’s gonna be. It’s gonna be very different than what we’re talking about today. I think equally enjoyable. Thank you to the speakers and have a good rest of your day wherever you are in the world. Thank you very much. Yeah, bye, bye.

Last Updated: September 8, 2023

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