Since the first retinal optical coherence tomography (OCT) images were published in 1993, OCT has played an integral role in the diagnosis and management of retinal diseases. OCT can be invaluable in retinal practice, however, artifacts can easily occur and failure to recognize them may lead to misdiagnosis and incorrect management of these disease entities.
Lecturer: Dr. Arghavan Almony, Ophthalmologist, Carolina Eye Associates, North Carolina, USA
During the presentation I’ll be asking you for some input and when you put in your comments or answers, please go ahead and use the Q&A section for that as well. I’m going to share my screen here.
For today’s presentation we’ll be discussing OCT artifacts in retinal imaging. I don’t have any conflicts to disclose for today’s presentation.
And we’ll begin with a few questions to get a better sense of who’s joining us in the live webinar today. How long have you been in practice? A, currently in school. B, currently in residency or fellowship training. C, practicing for less than five years. D, practicing for 6-15 years. And E, practicing over 16 years. Go ahead and submit your answers now. Okay. It looks like most are practicing over 16 years and then we have some who are in school or in training. A good percentage here. All right, we’ll go to the next, sorry, I’m going to try to close out of that.
Second question is what is your practice focus? Are you in medical school or residency/fellowship training, are you in optometry, general ophthalmology, medical retina, medical and surgical retina, or other? Go ahead and submit your answers now. Okay. It looks like about 40% are general ophthalmology, we do have optometry joining us, some retina, and some in training.
And finally, where do you practice? Africa, Asia, the Caribbean, Central America, Europe, North American, Oceania, and South America? We have more than half from Asia, about 16% from Africa, another 10% from North America, and 14% from Europe. Thank you for joining today.
I’d like to begin by considering the Louvre glass pyramid in Paris. This is an intricate fusion of traditional and modern architecture. It stands at the core of the Cour Napoléon in the courtyard of the Louvre Museum. And it has become a landmark for the city of Paris. I. M. Pei, an architect, was appointed in 1983 by president François Mitterrand to develop a new grand entrance to accommodate the growing number of visitors and to reorganize the Louvre Museum interior. It was Pei who designed the pyramid, the entrance of which opened in March 1989. Pei insisted on total transparency in the pyramid glass so that when visitors looked through it, there would be no perceptible change to the palace. His main challenge was to find the most transparent, flat glass possible to interact with the sky and the environment so that views of the courtyard would not be distracted. He also wanted to allow in as much natural light as possible into the museum.
Finding a clear glass presented a serious challenge because glass has a faint green or bluish tint due to iron oxides. He enlisted French manufacturing company, Saint-Gobain, to create a new glass specifically for this project. Months of exhaustive research went into the development of this 21.5 millimeter extra clear, laminated glass with its exceptional mechanical properties and high optical quality. This glass has, in particular, been cleared of its iron to avoid any green reflection or artifacts.
It took about two years to get this right. Removing the iron oxides required the company to construct a special furnace. There are 1800 square meters of glass in this pyramid. 675 lozenges, which is the rhombus-shaped glass that you see, and 118 triangles. These rest on a structure composed of 6,000 metal bars, bringing the total weight to over 200 tons. This is my husband and I in the Louvre before COVID. And you can see how clearly you can see through that glass to the buildings outside. The way that they went about this is to prevent artifacts from distracting from the original art that was to be viewed.
I think, essentially, millions of dollars and years of research went into this to allow the human eye to see the palace in all its majesty. I have to wonder how much more important it is for us, evaluating and diagnosing the human retina, to be able to see these images without artifacts. And so that is what we’re going to talk about today.
This is a OCT as we see it today. In 1993, Swanson et. al. published this paper showing the first images of in vivo OCT. And this is what it looked like at that point. We’ve come a long way and now this is what our OCTs can look like. You can see all the beautiful layers of the retina in this OCT.
This is a Cirrus HD OCT macular thickness analysis report. And this is mostly what I use in my practice and so this is what I’ll be using to present my cases today. There are, of course, other OCTs and brands and I think the talk today is really applicable to all of those.
Let’s just get familiar with this analysis report. Here we have the laser scanning ophthalmoscope fundus image and then inside it is the ILM-RPE retinal thickness map overlay. This is the ETDRS grid which is compared to normative data. Here we have the OCT fundus image. This shows us the cross second through the horizontal crosshair line. And there we have the image in the vertical crosshair line. This is a 3D macular thickness map, the ILM map, and the RPE map. And then here we have the macular parameters that which we can compare to.
Let’s get into it. Case number one. We have a 79-year-old man with decreased vision in the left eye. And this is the OCT as presented in the clinic. I’d like you to just take a second and put in the Q&A what you think this is. I’ll give you a few seconds to do that. Remember, we are not using chat for today’s presentation so please put this in the Q&A. Okay, so we have macular edema, cystoid macular edema, choroidal neovascular membrane, macular degeneration, lots of great answers. This patient was actually referred for macular edema in the left eye.
We’re going to watch this OCT as it goes through here. Were you able to see that? There we go, there it is. And we’re going to look at another view here. You see that initially this looked very much like macular edema. But if you look in the top right hand corner now you can see very clearly that this is, in fact, a full thickness macular hole. And there were a couple of those on the Q&A. Great job to those who answered that.
In the left slide, you can see the macular edema very clearly. But when you look on the slide on the right, that full thickness macular hole becomes quite apparent. And so what did we have to do here? We simply moved the raster. The image on the left was not focused on the fovea. If you look at the LSO fundus image in the top left cover of the left image, you can see that those crosshairs are not centered. You can also get a hint of the full thickness macular hole in the upper right image or the OCT fundus image. You can get a hint of that full thickness macular hole.
Here’s another patient. It looks like macular edema, possibly vitreomacular traction. And then as we scroll through, right, there it is. We can see that full thickness macular hole. Right there. But if we depend on the initial image, we’re not going to see it. The diagnosis is going to be incorrect and the management is also going to be incorrect if we depend solely on one single image.
Okay, case number two. 72-year-old woman with decreased vision. And this is what we see. Go ahead and put in the Q&A your diagnosis. I’ll give you a few seconds to do that. I’m getting drusen, dry AMD, dry MD PED, choroidal neovascular membrane, lots of PEDs, lots of drusen. I’ll give you five more seconds to put in your answers. Okay, more drusen, PEDs, excellent. This is really the PED that we are looking at and here we go. As we go through the different sections we see that subretinal fluid emerge. And it’s just a matter of getting a different cross section. It’s very easy in some of these cross sections to think that these are drusen or PEDs. But when we scan through we can clearly see the subretinal fluid that’s present. And there it is.
We can look at these different images for thickness, for various diagnoses, but really we’re looking for that subretinal fluid when we look at patients with macular degeneration. And so here is the cross section that we really would have loved to have looked at at the very beginning.
In the image on the left, we have a diagnosis of dry AMD. There is no obvious fluid. And on the right we have a diagnosis of wet macular degeneration or exudative macular degeneration. These are in the same patient, just different rasters. If we were to base our treatment on the diagnosis in the left we would simply observe the patient, while on the right we would give the patient an anti-VEGF injection.
Okay, case number three. A 45-year-old woman with poorly controlled diabetes. Here hemoglobin A1C is 14%. And this is what the OCT of the right eye shows. I’ll give you a few seconds, go ahead and put in your diagnosis based on the OCT. Okay. We are getting branched retinal vein occlusion, subhyaloid hemorrhage, edema, preretinal hemorrhage, and this is really the part that we’re focusing on right here. Another subhyaloid hemorrhage, another preretinal hemorrhage. There’s the fundus and this is preretinal hemorrhage. This patient was sent to me for macular edema based on the OCT. You can see how it can be confusing sometimes to determine what is actually going on. And here’s the preretinal hemorrhage. And this is a comparison of what the OCT shows. You can see the shape. And then this is the left eye in the same patient. And you can see here the same type of finding.
Now, I’d like to spend the rest of our time going through common artifacts in OCT. This is the first one. And looking at this, do you see any problems with the image here? Go ahead and submit your answers in the Q&A. Okay, we have one saying no. Lots more no’s coming up. Somebody said I see a problem, there’s black areas in the LSO fundus on the upper left and upper right images, but I don’t know what they are. Somebody says vitreous damage. Okay, very good. And this is what we’re focusing on here. Why do we have these black lines?
Here’s another patient, same thing. The first one had multiple black lines going through the image. This one has just a single black line. The horizontal and vertical images through the crosshairs look perfectly normal, we don’t see any issues there. But why are we getting those black lines? Somebody is saying vitreous opacity, vitreous damage, more vitreous opacity, poor signal strength. These are all great, great thoughts.
And a lot of you were able to get this right. Blink artifact. What are some things we can do to address that? Artificial tears to moisturize the eyes, we could ask the patients to close the eyes to rest for a minute. And the truth is we may need multiple scans to see all of the macula. But when you see those lines missing through the images, it’s just a matter of recognizing that this is blink artifact. In our first and second examples, the maculas were normal. The OCT images were normal. These patients did not actually have any foveal pathology. But it’s important to be able to recognize that because maybe you’re not getting the full image. We have some more answers coming in here. Floaters and then lots of blinking. Great job to those who got the blink artifact.
Okay, what about here? Do you see any problems with this OCT? Go ahead and submit your answers. Okay, I have a few nothings, everything looks great. A few that say media opacity, blinking. This is not blinking because we don’t see that line missing through the LSO fundus image on the top left or the OCT fundus image on the top right. If this was blinking we would see those missing lines.
More floaters, media opacities, okay this is what we’re looking at here. And this is a little tricky because, again, the horizontal and vertical crosshair line images look perfect. The top left image looks fairly good. The ETDRS grid in the upper middle looks fairly good. But if you pay attention to that top right image, the OCT fundus image, you can see there’s something going on there. And that is causing a little bit of change to the resolution that we’re getting.
In this example, it doesn’t really matter because this is a normal patient. But we want to be able to recognize these artifacts when it really does matter. For example, if the pathology is in the section where the arrow is pointing in the horizontal crosshair line. So hair artifact. And some of you were able to guess that on the Q&A.
Some things that we can do is if it’s bangs or the patient’s hair has just come forward, we can move their hair. We can ask our photographers to have some hairpins available to be able to pin the hair back so we can get nice, clean images.
Okay, how about this one right here? Go ahead and submit your answers in the Q&A. Again, I have more hair artifact coming in, great job. Somebody said moving, blinking, this is not, this could be blinking, you’re right. Usually with blinking the entire line is constant. On the upper right image, we do see that the lines are constant. On the left, they’re not all the way across. This is not blinking. And then you can see in the bottom left image, the vertical crosshair, you’re missing a lot of data. In a patient like this it would be difficult to make a proper diagnosis if we’re not getting the full data.
Asteroid hyalosis I have here, eyes not focusing, patient moving, okay. Here’s what we’re looking at here. And these are the areas that we’re missing which makes it very difficult to make an appropriate diagnosis based on this. Nystagmus. And what can we do for patients with nystagmus? We can isolate those ocular muscles to try to get a solid image. Some of the other answers were hair. This is usually not hair because we don’t get these vertical lines with hair. Someone else said dry eyes. This is usually, it can be dry eyes, but typically not. This is how we might be able to isolate the ocular muscles so we can get a full image of the macula.
Okay, how about here? We just talked about nystagmus. What do you think is going on here? Somebody says eyelashes, vitreous opacities, maybe asteroid hyalosis. What else? Somebody said nystagmus. This is what we’re looking at here. And then this is what we’re seeing on the vertical crosshairs which is significant. If this was a patient, we would not be able to make a correct diagnosis. We saw nystagmus on the last example and the OCT on the right is somewhat similar but definitely different. Definitely something else. I have a few more answers coming in. Eyelashes, dry eye, okay, so let’s see what this is.
Here’s another example. And you can see the ETDRS grid, the top middle image is also quite off. We can’t make any predictions based on that either. Here’s another example. Parkinson’s tremor. In these patients, it can help to ask the patient to keep both feet flat on the floor. That can isolate the large muscles and help reduce the tremor. Another trick is to ask patients to reach their arms up and actually hug the machine. Again, to reduce those tremors. These are all tricks that can help. Of course, there are some patients where these will not help either. But we’re just trying to get the best images that we can to allow for the correct diagnosis and subsequent treatment.
All right, here’s the next example, what do you think? Go ahead and put in your answers in the Q&A. And maybe you don’t see anything wrong with it. We have movement, dry eye, blinking, floaters, vitreous floaters, lots of that. Okay. Let’s look at this. When you look in the top left image, the LSO fundus image, there’s a double fovea and we know that that’s not the case for this patient. What is going on? And then you can see here that if we’re looking at that area for the pathology, we’re missing something. It’s going to be difficult to make the appropriate diagnosis.
Here’s another example of a different patient. And you can see that double fovea there. And if you look at the OCT fundus image, on the top right, we see that double fovea as well. Here’s another example. They’re not necessarily always on top of each other, they can be very inconsistent.
And you can see that the entire section there is not giving us correct information on the ETDRS grid. Poor fixation. And some of you did say that. How do we address poor fixation? We have to be patient, take multiple scans sometimes and that can help by giving us different cross sections in the different scans. And then sometimes it’s really helpful to use a brighter fixation light. Sometimes patients just aren’t seeing that light. If we brighten it, it can help to allow them to fixate, so that we can get a proper image.
These are getting harder, how about this one? This is a little more challenging. Go ahead and put your answers in there. Somebody says myopic fundus on this one. Another answer I’m getting is dry eye, lots of those. Several people are saying nothing. Nothing is wrong here. Seizure, fixation loss, dirty lens, somebody says sorry, no idea. At least you’re honest! Eye movement, another dirty lens. Another eye movement in seizure. Okay, let’s look at this.
This is what we’re focused on. The horizontal image below that, it actually looks quite normal. But we see in the vertical crosshair image below at the bottom left, that there’s something wrong there. We’re not getting the full image. And then we can see in the OCT fundus image on the top right, that we’re not getting a clear image. These are all the cues.
Following scanline. And one person said that, great job. What happens when a patient follows the scanline? Honestly, it’s just about being patient, doing the scan several times, reminding the patient to not follow it. And sometimes that’s possible and sometimes it’s not. But it’s important that we recognize it when we see it so we know when we get that OCT, that we’re not getting the full fundus and so we may have to redo that.
How about here? Go ahead and put that in the Q&A. I’ll give you just a few more seconds. I’m getting cataract, dry eye, lots of cataracts, dry eyes, edema, vitreous hemorrhage. A few more coming in. Floaters, poor signal strength, hazy media, poor positioning of the patient’s head, lig mass, ptosis, more media opacities and vitreous opacities, cataracts, and that the patient is moving away from the machine.
What are we looking at here? Although we’re getting an image, that image is not so clear here. And if we look at the image on the top showing the macular thickness, there’s an entire area missing. The ETDRS grid also shows us that there’s an entire area that appears to be missing. And then here, on the LSO fundus image, we can see that clearly as well. The important take away here is when we’re looking at these OCT images, there’s a lot of data on this analysis report. And sometimes we get in the habit of just looking at the left bottom two images: the horizontal crosshair line and the vertical crosshair line. But it’s important to use all of this data as cues as to whether we can trust the imaging that we’re getting. And that if we’re getting images that appropriately allow us to make a good diagnosis.
This is a small pupil. And sometimes we can dilate patients further and sometimes we can’t. There are some patients that are difficult to dilate for whatever reason. Something I like to do is a limbal rub where I put dilating drops on a cotton-tipped applicator and do a limbal rub gently for the patient. Sometimes that can really help with the dilation, sometimes it’s still a fixed pupil, a surgical pupil, or for whatever reason the pupil does not dilate. And at that point we have to take the image for what we can. That image can be repeated and several scans sometimes can give us multiple rasters of information so that we can put all of that information together to make a correct diagnosis.
Okay, how about this one. This is my favorite one. First of all, in the Q&A, can you just tell me, have you ever seen or received an image like this? While you’re putting in your answers, somebody asked me to explain the limbal rub again. You take a cotton-tipped applicator, you concentrate it with dilation drops. Really you just put as many drops as you can onto the cotton-tipped applicator, it will be soaking wet. And then you numb the patient’s eye and you rub the limbus to allow those dilating drops to get in a little bit better. A lot of times it will help for patients who are more difficult to dilate, not every time, but it can really help.
I have a lot of no’s here, lots of I’ve never seen this before, never seen this before. Somebody said myopia, somebody says cataract, any other thoughts on what this could be? Mirror artifact, geographical atrophy, just reading you some of the answers. (laughs) Somebody said inverted patient! I’ve never heard that one before but I like that one. Somebody said not focused on the retina, fog on the lens. Here I have a yes, I’ve seen this before, I don’t know what it is. The patient is not close enough to the OCT, high myopia, high myopia, never seen this.
This was referred to me for a patient with macular edema. And you know, if we think of this entire cross second as the edema I can see why this was sent to me. You can also see in the macular thickness map in the upper right, second from the top, that there is some red and yellow in the topography showing that there possibly is edema. What is going on here, I’m just going to give you a couple more seconds for some more answers. The scan is upside down? The scan is not upside down because this is the analysis report that we get. Somebody said ptosis, first time seeing this. Inverted lens? What if the lens is inverted, do we get this image? Okay, let’s look at this.
You can see that the foveal pit is upside down. The patient is positioned too high, that’s all it is. And all we have to do is lower the patient’s chin or chair. We all know that when patients are sometimes stressed in the slit lamp or in the OCT machine, their head keeps rising up and their chin is not completely down on the chin rest. And so it’s just a matter of recognizing that and lowering the patient’s chin or chair.
And the other thing to know about this is some people actually use this image on purpose. When they’re taking the OCT image, they on purpose position the patient too high to be able to obtain this kind of image. And that’s because it helps us get more details of the choroid. This would not be something where we’re looking for foveal pathology, this is something where we’re maybe interested in choroidal pathology. And there are people who look at this. Somebody says for choroidal thickness. Yeah, exactly. If we’re looking at the choroid and we want some more details, this is a great way to do that.
Okay, how about this one? What do you think is going on here? Go ahead and put your answers in the Q&A. You guys know this one. We have high myope, staphyloma, here’s where we’re looking. And you can see that the ETDRS grid is completely off based on normative data. Here’s another one. Not as pathologic, but you can see that in the upper left image, the LSO fundus image, and the upper right image, we’re not quite seeing everything. You can see in the thickness map that there’s a section missing in the top left of the image. Something’s going on here. Let me see some other answers here, so staphyloma, high myopia, staphyloma. You guys got this.
High myope. Remember that the machine can actually calibrate up to +20 diopters and -20 diopters. And then you can always leave the patient’s glasses on when they’re a high myope. That’ll help obtain the best image in these high myopes that we see.
All right, next one. What do you see here? Go ahead and put your answers in the Q&A. I have some more myopes, myopes, floaters, vitreous hemorrhage, eyelash. You know, eyelash is going to be a little more wispy looking. And I don’t have any eyelash artifacts in this presentation today. But we won’t see that debris in the horizontal crosshair or the vertical crosshair line. We also, if you look in the top left and top right images, you see that there’s an entire area missing there. We’re not going to see that when we’re looking at eyelashes.
Let’s see what else we have here? A Weiss ring, more vitreous hemorrhage, lots of vitreous hemorrhage. Myope, more myopes, blockage from a Weiss ring. Let’s look at this. This is what we’re looking at here. And you see that an entire section is missing in the horizontal crosshair. If the pathology that we’re looking for is there, this can be a problem. And this is the fundus image of a similar patient, for all of you who said PVD, you were corrected. Excellent job.
Here’s the next one, what do you see here? Go ahead and put your answers in the Q&A. We’ll give you a few seconds. We have more myopia, more posterior staphyloma, choroidal neovascular membrane, myopia, cataract. We see in the LSO fundus image in the top left, that there’s an entire area missing. In our horizontal and vertical crosshair images, we see part of the OCT. And that looks fairly normal. But about half of it is missing. And then in the OCT fundus image on the top right, it’s a big blur. We’re really not getting any data there.
In these situations, if it’s available, I like to use a Vscan ultrasound. And here we can see a vitreous hemorrhage. This is a more pronounced OCT showing the vitreous hemorrhage, it’s quite beautiful. With the retina clearly visible and then the vitreous hemorrhage overlying that, or the preretinal hemorrhage overlying that. And this is what the patient would look like in a situation like this. So vitreous hemorrhage.
How about this? Go ahead and put your answers in the Q&A. What are we seeing here? I have preretinal hemorrhage, posterior staphyloma, hazy media. There is something going on there. The question is, is it important? I have small pupil, media opacity, cataract, vitreous hemorrhage. Somebody said asteroid hyalosis, patient moving away, vitreous opacity. Lots of I don’t know, not certain, which that’s why we’re here today. Vitreous floaters. Okay, let’s look at this. There it is. For those of you who said asteroid hyalosis, you were absolutely correct. And this is what asteroid hyalosis will look like.
We just have a few more here before we wrap up. Go ahead and put your answers into the Q&A here. Somebody says not centered, somebody says blinking. Somebody said staphyloma, another not centered. All right, what are you seeing? Staphyloma, somebody said epiretinal membrane, another epiretinal membrane. Another epiretinal membrane, so lots of epiretinal membranes here. I’ll give you just a few more seconds. Somebody says preretinal hemorrhage, someone else is saying vitreous cell. Uveitis, somebody is wondering if this is an aqueous. All right, let’s look at this.
This is what we’re looking at here. You can see that red line. And we know that this is centered over the fovea because we see that foveal pit right there in the center. It’s not great because that line is disrupting it. But we know we’re centered. Silicone oil. There were a few people that guessed vitreous things and that’s true. We know that this is not an epiretinal membrane because with an epiretinal membrane we’re not going to get that red line. We will get a white line but not that red. And the reason for that is because as that light is going through the various tissues, epiretinal membrane is much closer to retinal tissue and so the colors are going to be similar to retina colors. Where silicone oil has a much different consistency than the retina. And so that’s why we get a huge change at that vitreous-retina interface with a red line.
Somebody else thought maybe drug particles like remnants, Kenalog, after surgery, and then lots of epiretinal membrane. It’s important not to confuse this. Of course you usually know the history of the patient, you know if they’ve had surgery with silicone oil, but sometimes you don’t. Sometimes you’re consulting, sometimes you’re not seeing the patient. It’s important to be able to recognize that.
All right, what about this one, this is the last one. Is there even anything wrong here? Somebody is saying eyelid, RPE migration, eyelid, ptosis, lid artifact. More eyelids, coloboma, coloboma, coloboma. Okay, very good. Let’s look at this.
Here’s what we’re looking at and if this were coloboma it would make sense why someone would look at that and say coloboma. But it’s a gas bubble. And a lot of you got that right. After we do vitrectomy surgery, if we put a gas bubble in the eye, that’s what we’re going to get.
I’d like to wrap up with some take home points in looking at these examples. First of all, any time we look at an OCT, we want to look at multiple rasters and scans. You remember when we looked at the patient that was referred for macular edema, that was in fact a macular hole, if we had just looked at one raster we would have misdiagnosed as macular edema. But when we actually look at all of the rasters, and scroll through, we can see that full thickness macular hole quite clearly.
Take home point number two, we want to pay attention to the entire set of data. In this analysis report, the horizontal and vertical crosshair images are completely normal and this is a retina that doesn’t really have any pathology. But we want to pay attention to the quality of the image that we’re receiving. We always focus on all of the data that we are receiving. If we look at the top left and top right images, we see that we’re missing some chunks of data there. If we look at the ETDRS grid as well as the maps on the right side, again, we’re missing some data. It’s important to be aware of that because that missing data could be important pathology that we’re not able to diagnose because we just don’t see it.
When we have a patient with nystagmus or tremor, we want to isolate the muscles. In Parkinson’s we talked about having the patient with both feet flat on the floor. Sometimes it helps to have the patient actually hug the OCT machine, again, we’re trying to isolate as many of the large muscles as possible to get the best images that we can.
You were all able to diagnose this one quite easily. When a patient is high myope, we can ask them to wear their glasses during the OCT and that can be a big help.
And then finally, and you all know this, but repeat, repeat, repeat. If we don’t get a good scan, then we do it again. Or we use multiple scans to give us the information that we need. And finally, to be patient with our patients.
We have a few minutes now for questions. I want to thank you for your time. And so if you have questions, please go ahead and put them in the Q&A. And we’ll try to get to as many as possible. But thank you for your time and thank you for joining us.
Somebody made a comment here that most of the artifacts are diagnosed and corrected by the operator. And that’s true. Some of my photographers and technicians are really good. They have years and years of experience. There are other ones that are completely new. And so as the physician and as the person who is receiving those images and making diagnosis and treatment choices based on these images, it’s important that we know when there’s artifact, when we have to take the patient back to the OCT for a repeat scan or for multiple scans.
Somebody’s asking, do you take your own OCTs or a technician or a resident? I have photographers and technicians who take the OCTs as well as fundus photos, fluorescein images, and ultrasound Vscans. And fortunately, like I mentioned, sometimes they’re new, sometimes they’re inexperienced. It’s important that we know the quality of the images that we’re receiving so that we can set a high standard for those that are just learning. And so that we know if the quality of the images that we’re receiving is appropriate for making a diagnosis and treatment decisions.
Someone is asking about the limbal technique again. Sometimes patients do not dilate very well. You put in the dilation drops and 20 minutes later, 40 minutes later, they’re still not dilated. You can put in a second set of drops and then again, let’s say, you give them some time and they’re still not dilating. In some instances, a fixed pupil, a surgical pupil, it doesn’t matter what you do, that pupil is not going to dilate. But if a patient just has a hard time dilating, what you can do is take a cotton-tipped applicator or a Q-tip, douse it with dilating drops and it’s going to be really soaked. And then you numb the patient’s eye and you can just do a gentle limbal rub at the limbus, several rubs. And that really helps to penetrate the dilation drops.
Somebody asked what the animal in the picture is. You know, my son asked this question as well. This is a bird that is found in Antarctica. My son and my husband were lucky enough to go a few years back. And so this is a very blown up picture of that bird. And I cannot remember the name of that bird, so I’m sorry.
Just trying to read some questions. For high myopic patients, is it better to try with a contact lens or glasses or are they the same? I find that for high myopes, contact lenses are actually a better option in terms of getting the best OCT possible. That contact lens gives you a more clear view into the posterior segment. A lot of patients don’t wear contact lenses and they wear glasses, so it’s important to make sure the lenses are clean. But they both work. I just find that especially for the highest myopes, contact lenses can make the images a little bit better.
It’s 10 o’clock so I’m just going to do a few more questions and let you all go. Let’s see. The other question that I’m getting a lot of is what is the best signal strength for the retina and choroid? To be honest, the best signal strength is what allows you to get the best image without artifact. Sometimes the patient’s eyes are very dry, sometimes there are things that are going to impede that signal strength like a cataract or vitreous hemorrhage. I don’t think there’s a specific number, I think it’s a matter of taking out as many of these artifacts as possible so that we can get the best image that we can. Sometimes even with all of these different tips and tricks, the image is still terrible. That doesn’t mean we can’t use the image, we can still use the image as clues to try to make the final diagnosis. But the point is to try to get the best image possible to make your job as easy as possible.
I want to thank you, again, for joining today. I hope that this was useful. And I hope you have a good day.
January 21, 2022
3 thoughts on “Lecture: Red, Green, and Yellow Disease: OCT Artifacts in Retinal Imaging”
Thankyou for the informative talk. A few tricky ones in there.
It was informative