During this live webinar, the following objectives will be discussed: Appreciate the advancement in optical coherence tomography technology, identify normal retina OCT, interpret retina OCT with a systematic approach, localize retina pathology, and form a differential diagnosis based on OCT.
Lecturer: Dr. Peng Yan, Department of Ophthalmology and Visual Sciences, University of Toronto, Canada
I have no financial disclosure related to this topic. But I do like to thank Cybersight, Orbis, and Lawrence for inviting me for this opportunity. I do want to bring to your attention to those who are interested in learning more about OCT cases. This is a website that my colleagues and I put together and it features many of the OCTs, including retina, glaucoma, numerals and eventually cornea and OCT angiography. It’s a free, virtual platform that we hope to spread around the world. And in return all we ask for those of you who enjoy the website to contribute their cases so then we can actually bring more cases to audiences around the world.
The objective of today’s education is to appreciate the advancements of optical coherence tomography technology and how dependent we are on a day-to-day basis especially for a busy retina clinic. And be able to identify normal and therefore in order to diagnose pathology. And also, as we all know, not all the times we know the diagnosis. Therefore be able to interpret retina OCT and isolate the location of the pathology often will help you narrow down your diagnosis or potential diagnosis. And of course to appreciate some of the updated macular OCT signs. I know some people expressed interest in learning the interpretation of optic nerve. And those should also be uploaded later on in OCTcases for those who are interested.
We have to pay respect to those of our predecessors who developed the OCT in 1991. We can see how far we have come from the images that initially in 1991 to the image that we’re able to get today which are fast, in office, and without dilating the patients often. We’re able to see almost live pathology. And hopefully with advancement of technology we’re able to see more of a cellular level. We already are able to explore the choroid, right? With advancement of enhanced OCT. And also OCT angiography. I know a lot of people expressed interest in learning this but I added a few slides on this as well in this presentation.
A really quick word about obtaining OCT images in your busy practice. The first thing you do is to make sure the quality of the image, the name of the patient, the eye, the unilateral tomography of the eye, the date of the acquisition. And before you proceed, so you know you have the right patient, the right eye, and the right date. Often the picture you’re presented might not be the right slide. For example in this case, the patient presented with vitreomacular traction with disturbance of outer retina, presenting as an impending hole our guess. However for those who are astute, if you look at slide number four, there’s already formation of a macular hole. It’s important to scrutinize the slides that we have and admission with you or a forum where you can scroll up and down the slide, that would be great. Some people mentioned the different scanning patterns and that’s also very important in determining what you want to do. A single line for a rapid scanning of the macula or area of interest. And radio lines for determining a source of pathology that you can discover. And a five line raster usually I’ll use for the macula.
In order to diagnose pathology, we have to know normal. And these are readily available online and on OCTcases where first you should understand what the normal retina looks like and how the different layers present itself. And what are the cellular components? And that will help you isolate this pathology why certain diseases happen.
Let’s start with a warm up quiz and then we’ll have a post lecture quiz. Question number one, is which of the following image is a pseudo-hole? If we could launch a poll, that would be great. That is great.
Great, now question number two. Which of the following contains retinoschisis? And what findings are present of this particular OCT? Is it 1, vitreomacular traction, presence of epi-retinal membrane, presence of retinoschisis, or macular edema with presence of intra-retinal fluid? Or can this be a combination of 1, 2, 3 or is it all of the above? Excellent.
And moving on to the next one. Which of the following is reticular pseudo-drusen? We all see drusen on a daily basis and this is our bread and butter of retina clinic or image ophthalmology clinic. With advancement of technology we have access today we should be able to differentiate various types of drusen that get associated with emulsification. Given distribution there’s lots of answers.
And finally what is the diagnosis of this? And also think to yourself how you would describe this OCT finding? And as we’re doing the poll I just want to bring everyone’s attention to the fact that as an ophthalmologist for eye care professional, we’re very privileged to have access to the various imaging modalities and making us almost our own radiologists. We don’t have just access to OCT, we have OCT angiography, fluorescein geography, ICG, autofluorescence, Vscan, and various imaging modalities. It is really fun and a good time to process imaging for the eye. This is great. Also distributed between 1, 2, and 3. We’ll go through all of these questions throughout the presentation and then we’ll do this again.
For the purpose of my talk, I would like to divide the OCT interpretation into five different zones. And I’ll tell you why. Zone number one is the vitreous cavity. Zone number two is epi-retinal or vitreoretinal interface, zone number three is intra-retinal which is fairly divided to your inner retina, outer retina. Then we have our sub-retinal space. And followed by choroid which with the advance of imagining we’re able to explore a little more.
The vitreous cavity is probably the easiest of all the zones because we don’t really need OCT for this. There’s only a handful of conditions in the vitreous cavity here. The vitreous is made up of 99% water and therefore should be optically transparent. The only reflection we should see is the posterior hyaloid.
When we do see something in the vitreous, and someone mentioned this in the pre lecture question, how do you know something is artifact? In this case, we see these hyper reflective material in the vitreous cavity. How do you know this is not artifact? You look for a transmission defect. If these are truly in the vitreous, then the light that it transmits should not pass through as you see in the red arrow. And if you can see my cursor, my mouse here, you will see this sort of light blocking transmission defect signaling that these are truly present in the vitreous obstructing light. Hence casting this shadow on the retina. What can this be? These are large refractile bodies in the vitreous cavity, we could also see this in another case of asteroid hyalosis.
Here we have another case of something in the vitreous cavity. Presence with hyper reflective dots and also this hyper reflective band which is somewhat associated with the posterior hyaloid which has lifted off from the surface of the rim. At the same time we see these little deposits on the surface of the macula as well. You know these are not artifacts and they are truly present not far off from the surface.
One of the questions that we’re commonly asked, if you see the posterior hyaloid, say within the scan of our OCT image, will you call this PVD? Of course our answer is no because PVD is defined by lift off of your Weiss ring. And in the image of OCT, often the distance, even the thickness of the retina is about 250-300 microns, and so this distance between the hyaloid and rim, very narrow and therefore usually the detachment not occurrence. In this case you have subhyaloid hemorrhage in the patient with proliferative diabetic retinopathy who requires surgical intervention.
And finally the last thing that is very common we see in the vitreous cavity are these hyper reflective foci just saw for the red blood cells. In this case it’s associated with a fluffy deposit on the surface of the retina. And these are usually associated with tragus in the case of endogenous fungal endophthalmitis.
And that’s it. The pre-retinal zone is covered and we move on into the epi-retinal or vitreoretinal interface. The zone most interested from most retina staff. And surgical retinal especially. Most of the vitreomacular interface pathology are a result of posterior hyaloid detachment. For example we have vitreomacular adhesion or the detachment of posterior hyaloid from the retina surface. When there’s a tight adhesion it often results in intramacular traction. And with sufficient traction you can lead to macular hole and epi-retinal membrane in the context of PVD usually result from a somewhat traumatic vitreous detachments. Leaving little microabrasions over the internal limiting membrane. We all know that internal limiting membrane are the foot processes of Muller cells. Or when these internal limiting membrane gets disrupted we can get hyperproliferation and hyperproliferation of internal limiting membrane whether there’s sufficient traction and muscle schisis and detachment.
Everything we discussed would be in accordance to the 2013 International Vitreomacular Traction Study and so that way we keep everything consistent and uniform.
The first pathology is vitreomacular adhesion and this is the perifoveal hyaloid detachment without disturbing the architecture of the macula. And of course if there are any vitreomacular traction adhesions we define by the width of this attachment. Focal or broad which is. And the red arrow shows reflection of the posterior hyaloid with attachment to the fovea and depression.
Foveal vitreomacular traction leads to a more tinier adhesion over the fovea and as the posterior hyaloid lift off the process of posterior vitreous detachment, you will see a presence of drying fluid or schisis. And of course with sufficient traction you would see a full-thickness macular hole. Of course posterior hyaloid detachment does not equal to posterior vitreous detachment. Which I discussed earlier, requires critical diagnosis in presence of a Weiss ring because that’s where the adhesions vitreous rear end.
How do we describe these on OCT? Every time we present with OCT we view these like a radiologist. We will look at the vitreous cavity as optically empty, the presence of the hyaloid and vitreomacular traction, leading to blunted foveal depression or in this case a thickening of the foveal depression. As it’s the inter-retinal cystic cavity and also disturbance of the outer retina involving the intra-retinal layer which I’ll talk about shortly.
You can see this red yellow arrow point to an inwards and bending form of the outer retina secondary force of traction on the retina vitreomacular inward. And this is a sign called the cotton ball sign. And usually is a good prognosis. Sometimes after a spontaneous release of vitreomacular traction, surgical or spontaneous, remains a presence of epi-retinal membrane despite complete resolution, you can still get this residual cotton ball sign. And sometimes we mistaken these for either pseudo-vitelliform dystrophy or for CHR, you can actually see these as a residual of post vitreomacular traction and in time these will resolve.
In this picture we also see presence of epi-retinal membrane. In a recent publication the rate of spontaneous release of vitreomacular traction with a presence of epi-retinal membrane.
Here’s another case of vitreomacular traction syndrome with presence of vitreomacular traction resulting in the development of a vitreomacular hole. And sub-retinal fluid with foveal detachment. And also your presence of these hyper reflective dots in the vitreous sub-retinal space. These are most likely from chronic detachments or RPE cells.
What about this image? This is an image of left eye. To tell the left and the right eye, we often look for the nerve fiber layers. Usually these are the green arrow indicates the thickening of the retinal nerve fiber layer which is usually next to the optic nerve head. This is an image of the macula of the left eye. We can see the vitreous cavity is clear and at the surface of the retina we see these tiny membrane which is presented as a hyper reflective layer having contraction and thickening of the retina and that’s labeled by the yellow arrow. Loss of foveal contour, we don’t see the foveal depression or foveal pits. And also we see that the inner retina layers are uniformly distributed and as we all know in the foveal region we should see many layers. Therefore this is ectopic inner retinal layer.
This is important where epi-retinal membrane staging, especially for surgical retinal specialists. In addition to vision itself, the staging of epi-retinal membrane is also critical. In this case picture number three, we can also see the presence of schisis here. The staging of epi-retinal membrane is number one, presence of epi-retinal membrane labeled by the orange arrow with preserved macular contour and foveal depression. Stage two is basically stage one with blunting or thickening or loss of foveal depression. Stage three is your epi-retinal membrane, thickening of the fovea, and also you can see the red arrow points to the inner retinal layers being drawn towards the fovea. And of course, then this basically brings it to the ectopic inner retinal layer. And stage four will be stage three but with this organization. However, for surgical retina in the treatment of epi-retinal membrane, I still base it more on patient symptoms. However, outcomes show in previous studies for stage two, beyond stage three to stage four, the outcome is. Because of the disruption of the changing.
One of the OCT modalities not commonly used is the retina thickness map. This is also very helpful in determining surgery. Especially in this case you can see areas of epi-retinal membrane and you can, based on this, decide where to initiate your membrane peel procedure.
What about this condition which is going to be associated with epi-retinal membrane? We see that the vitreous cavity is normal and the orange arrow indicates the presence of epi-retinal membrane. The blue arrow is indicating that is observed, therefore this is not a macular hole, this time appears like a macular hole. We call this a pseudo-hole. But what are its features? The features is that its foveal depression is very exaggerated and you can see that the edge of the macular foveal depression is straight and smooth. Almost like someone is standing on the side of a cliff.
And this is a condition called a pseudo-hole. Here’s pictures of three pseudo-holes. They’re usually associated with epi-retinal membrane. And the edge of the pseudo-holes are usually straight. And as you can imagine, like someone standing on the side of the cliff you jump off the cliff and therefore that’s a pseudo-macular hole. These are going to go to surgery although most of the time they’re very stable with vision and intervention is warranted in patients where there’s progression.
What about this particular case? Also looks like a pseudo-hole, doesn’t it? But what’s different is that the edge of this foveal depression seems to be chipped, almost like someone took a bite into it. And the outer retina is intact. Therefore this is not a macular hole. The shape of this chip region, intra-retinal, it’s in the shape of an anvil. And therefore this is called a lamellar hole. Associated with lamellar hole is usually pretty stable vision and it’s believe to be at the roof of a retinal cyst. You can imagine previously there’s a cyst and it’s been deroofed, then you get this sort of structure. It’s usually, surgery is not warranted and vision loss. You can imagine there’s a missing piece and we need to put this back together. However surgery is warranted in visual operation especially with.
In this image you also see presence of and this structure. Hyper reflectivity on the surface of the retina as you can see on my cursor here I’m not sure if you can all see this, but the green arrow labels this pseudomembrane on the surface of the retina. This is distinctly different than epi-retinal membrane and it is called epi-retinal proliferation associated with lamellar hole. This means that the contractile elements as we see in epi-retinal membrane, is not the same as this epi-retinal proliferation. This membrane does not contract and therefore this hole is unstable over time. If you’ve ever done surgery for these lamellar hole related epi-retinal proliferation, these membranes are very sticky and they appear yellowish in consistency. But there’s a distinct difference. When it presents in cases we differentiate with and epi-retinal proliferation associated with lamellar.
Now we look at the different images we should be able to differentiate between epi-retinal and lamellar hole. In picture number one, we see this sort of straight edge like if you’re standing on the side of a cliff. This is a pseudo-macular hole. Picture number two we see this anvil sign associated with this hyper reflective membrane that’s very smooth without any corrugation therefore means there’s no contractile flex. That’s the lamellar associated epi-retinal proliferation. With picture number three, a lamellar defect with the part of the retina being chipped. And number four with a pseudo-hole with corrugation of the retinal surface indicating presence of epi-retinal membrane and also straight foveal hinge.
Sometimes a lamellar hole, although rare, can convert to a full-thickness macular hole as we will see in this case. This case has a lamellar defect with intact outer retina. Presence of epi-retinal proliferation. And as we follow this case, you can sort of faintly see what we call a subchovial stress line. For those who are interested you can always look this up. Subchovial stress line usually happen in any sort of macular hole. It’s usually right in the middle of the fovea and you can see a very faint subchovial stress line. And of course it’s open up, you have a full thickness macular hole with lamellar defect presence of epi-retinal proliferation. It’s very full thickness and notches to do a peel. I usually like to peel the membrane and drape over the macular hole and tucking our epi-retinal membrane into the hole to treat both macular hole and the lamellar defect. And therefore you can see part of the internal imaging, not only resolving the macular hole but also the lamellar defect with a reasonable visual outcome.
Now we move into the intra-retinal space which is the majority of where the retina conditions and macular pathologies are. There are so many different conditions due to time restrictions we will briefly discuss some of them. The most important point of this presentation is not that by the end you’re able to inform the diagnoses, but rather be able to identify the regions of the pathology and then you can generate a reasonable diagnosis and narrow down your differential.
Let’s take a look, one of my favorite conditions is macular hole. I could give a whole talk on this subject itself. A macular hole is a clinical diagnosis. Waltzke-Allen test is basically bringing the slit lamp and get really slim and go over the macular hole and as the patient is broken or not broken then yeah, it’s positive for a macular hole. We also have the red free and also the gold standard is OCT.
If we talk about macular hole we have to pay respect in order to Gass classification without OCT was the only way to diagnose macular hole. But also being able to describe a macular hole in such detail with only the use of slit lamp and indirect ophthalmology. He was able to just look at the macula under the slit lamp and in certain stages. And that’s something we can do. But fortunately I have access to OCT. But nevertheless, this staging really is our universal set in macular hole strategy, especially amongst the retina community.
Stage 1A is contraction of inner retina, blunting, foveal pseudocyst and clinically you see these little dots. Stage 1B is the disruption of outer retina lumen, we see all this and both stage 1A and 1B will resolve in 50%, no surgery needed, observation is warranted. In this case, this outer retinal disturbance also has a name and of course there are many names, many signs. Some are actually useful. This is called subfoveal translucency. Essentially what it means is that there’s an outer layer defect. Sometimes, even after the repair of retinal detachment, vitreomacular traction, macular hole, you could still get this subfoveal translucence. In fact, that with time it may recover. There we go.
Stage 2 is a small macular hole that’s less than 400 microns. And this is associated with posterior hyaloid and some interesting attachments. Stage 3 is, of course, larger macular hole and more than 400 microns with associated with sub-retinal detachment. A stage 4 is your large macular hole with PVD subfoveal translucence.
Now, of course, in the era of OCT, we make our diagnosis in consultation based on these images which makes it a lot simpler. We have full thickness macular hole with or without vitreomacular traction. And without the hole is it primary macular hole so idiopathic. Or is it secondary post trauma, high myopia, or myopia and so on. And we define them as small, medium, or large macular hole. And of course it’s associated.
For smaller macular holes with focal vitreomacular traction treatment it includes observation or pharmacological vitreolysis with ocriplasmin. And also equally we factor pneumatic vitreolysis using C3F8 or SF6 gas. Before we do any pneumatic vitreolysis by a lot, you have to thoroughly examine the peripheral retina and pathology otherwise it will induce a retinal tear.
In the case macular hole and foveal detachment, I calmly embrace an intra-retinal gas bubble, patient face down and surgical attachment with the macular hole and focus getting to surgery making it much easier than, a bit more challenging.
For our larger macular holes, and much larger vitreomacular adhesions more than 1500 microns, surgery is warranted.
Of course the success of macular hole repair is fairly good. Back in the days with simple vitrectomy the hole will usually close less than 10 percent simply doesn’t close due to many reasons. Based on OCT, we’re not only able to diagnose macular hole but we can also allow us a surgical plan. For example, keeping this very simple, the edge of the macular hole here’s a drawbridge. If you imagine this looks like a smaller macular hole that looks relatively fresh and you can imagine this drawbridge coming down and achieve closure.
Now if you look at the picture below, this is a larger macular hole with what we call an open, the hole is open, and slot formation so that the edges of the retina has sort of stuck down to its new location. And for this edges to come together pretty much require the lifting so this is hard to reattach itself. Therefore it’s much harder and probably warrants surgery. A tuck is limiting a transplant or amniotic membrane where autologous transplant.
That’s how we use OCT image to plan for surgery. And I prefer calling it a drawbridge or a broken bridge.
This is an international patient who traveled to Canada. She had three surgeries including the use of silicon oil and of course at this point there is no healing after the surgery. And so the decision was to use amniotic membrane. Also we’ve got 304 we can see that there is the very nice inside amniotic membrane on this photo and OCT. We can see coatare of macular hole with presence of amniotic membrane from restock to the surrounding edges on the macular hole. With time gliosis will occur and I’ll measure.
Moving into the different layers of the retina. Number one is nerve fiber layer and we look at myelinated nerve fiber layer as an example. We all know myelination of nerve fiber layer is a congenital condition. Patients are usually asymptomatic and the reason is because they have this congenital condition which leads to visual field. We know it corresponds with a sarcoma. The reason is because of OCT we can see myelination of nerve fiber layer. Myelin induces a hyper reflectivity and this light blocking as we can see this transmission tracks. Just blocking off the transmission. And that’s why they don’t see very well in that area.
Similarly with myelination of nerve fiber layer has its sustained thickening and hyper reflective bands over the nerve fiber layer.
Here’s another example of nerve fiber layer widening. What we see is posterior hyaloid face which indicates that this patient is relatively young. With essence of these hyper reflective dots. We already know, there’s only a few field of visions that’s into these dots. That they’re tragus or it could be hemorrhage. They’re hyper reflective of nerve fiber layer associated with thickening of the fiber layer. Of course because of edema of nerve fiber layer you get blocking of lights and ulceration of those retina images.
This is an image of a cotton wool spot in the context of a patient who presented with hemorrhage, cotton wool spot, retinal hemorrhage and leukemia patient that mimicked the diagnosis of diabetic retinopathy. What’s important to highlight here is presence of cotton wool spot.
Any circumstances when we see cotton wool spots the patient warrants a work up because when you have cotton wool spots, it’s abnormal. Although they are cases it certainly warrants a case of screening for. When you CBC for cases that are warranted or have history of HIV, endocarditis and of course leukemia.
Other conditions that cause nerve fiber layer edema and swelling is central retinal vein occlusion and also central retinal artery occlusion.
And now we talk about the varieties of macular edema. There is secondary to diabetes, retinal vein occlusion or it can be from uveitis, birdshot syndrome. Macula edema is a disruption of the inner blood-retinal barrier, essentially the blood vessels, leakage of perifoveal way, leading to accumulation of fluid within the intra-retinal space. Mainly in the inner nuclear, outer nuclear and outer plexiform layer. And of course what is being leaked out is not simply just water. What’s being leaked out is usually plasma which contains proteins and so on. Therefore the consistency of the intra-retinal fluid, the edges between the different cysts can give us a prognosis feature of the swelling.
This is a slide that I kept since I was a resident and to me it’s very helpful for differential diagnosis in macula edema. It’s called DEPRIVENS. I’m sure that the pneumonics is a good one to have because macular edema is very common, especially post cataract surgery and vision post period bleeding and so on.
And of course there’s also another category called pseudo-macular edema. Pseudo-CME are macular edema where it appears to look like macular edema but they do not leak. Juvenile retinoschisis, certain types of RP and does not induce post op differentials.
Let’s take a look at how OCT can be a prognostic feature in many conditions. In this case we’re going to talk about diabetic macular edema. Of course diabetic macular edema and this is associated with diabetic process and it’s a huge topic of itself. But in this picture you see the varieties of diabetic macular edema. And it emphasizes this. If we just look at the picture and call it macular edema, we’re missing a lot more information. The size of the intra-retinal cyst more than 200 microns, the location of the cyst, the orientation, the structures adjacent to the cyst, content in the cyst, presence of macular aneurysm, the presence of cyst, hyper reflective full size, the abnormality of the diabetic pathology, all plays a role in outcome of this treatment.
This is a condition that we see in diabetes and loss of retinal vision. A plume sign with the intra cystic cavity hyper reflective material. What it signifies is a severe disruption in the vasculature leading to leakage of material. And of course you can imagine the treatment that would be more resistant and be more anti-VEGF but also use of steroid.
Here we see the columns in this cystic macular edema in this case the columns are considered to be either Muller cells or bipolar cells. And that’s why for many patients with their vision remains good, because the connection and the transmission of all signal is still present, as you imagine. The larger the size of the cyst, more stretched and more chronic it is, then you’re going to, over time, damage these retinal structures. When there is loss of these and fusion of these processes, then the visual outcome and responsive treatment is significantly. And at the same time when there’s larger cysts and contacts the ileum, sometimes the macular.
Hyper-reflective focis in the context and in vascular leakage symbolize the protein materials released from breakdown in the range of blood-retinal-barrier. And they are thought to be precursors to hard exudates. Which are not something you want to see near the fovea as. The yellow box highlights the presence of hyper-reflective foci and the green arrow points to hard exudates. And of course both are very close and they’re parafoveal. And as you can see these posts are light blocking because they’re cholesterol contents and that’s a solid particle in most light. When these particles comes to within the foveal region, it will cause patient to have significant vision loss.
Another good OCT biomarker or prognostic marker for visual outcome is this disorganization of the retinal inner layers. We can use this not only in macular edema but also retinal vein occlusion and so on. Essentially what it means is that you look at the layers of retina and let’s say a patient presents with macular edema, in this case diabetic macular edema. Someone asked the question: what’s the difference between diabetic macular edema and macular edema of retinal vein occlusion or uveitis? Usually the simple answer is macular edema looks a bit dirty. And the reason is because for diabetes, you’re leaking not only fluid but protein material. Also there’s presence of hard exudate and presence of microaneurysms. The entire picture doesn’t look clean.
Whereas, we’ll go back to a picture of macular edema secondary to retinal vein occlusion, that’s what we see in this top right hand corner. You see that picture is very clean with clean hollow cysts. And these are usually macular edema due to vein occlusion in process. Whereas you look at the pictures of macular edema from diabetes, there’s always something in there and fluid is not as clean. That’s just a simple way of looking at it for myself at least.
And so look at the disorganization of inner retinal layering. Basically it means are you able to decipher the different layers or the different layers of the inner retina? Here the yellow line delineates nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer. When these layers are still present, you predict that visual outcome should be good with treatments. And of course vision comes clearly and you can see preserved by inner layers of the retina.
Whereas in this patient, who had chronic macular edema, including having to treat with vitrectomy surgery. The yellow box highlights reattached retina here with no macular edema, but diffusely uniform homogeneous so that you can’t really isolate the different layers. This is the loss of retinal layers and therefore is a prognosis for visual acuity. And of course this patient with macular edema has.
How does this picture compare to the macular edema that we seen previously? We see these are all now oval in shape, or rather you have these vertical bridging columns. And this is a feature of a condition called retinoschisis. The yellow arrow points to inner retinoschisis which is less common than they occur in the layer of nerve fiber layer. The alter retinoschisis and usually patient have very good vision. And the reason is because just like what we discussed for DME, the connection is still there except that the layers sort of split a bit causing a bit of stretching of the Muller cells bipolar cells. The transmission of signal is still present. Retinoschisis aside of isolating to now foveal schisis, one of the most common cause is myopia. And it starts due to pinnacle stretching and elongation of the leading to some stretching.
The bridging column is the features in schisis and here’s some other examples. They all look the same. These are a lot of the OCT patients are basically how to recognitions. If you recognize one, sometimes you’ll be able to recognize other patients.
Let’s put this all together. This is a patient of 44-year-old Asian female, presenting with bilaterally, her picture is this, her vision 20/200. What do we see here? First of all, we see presence of concavity here, thinning of the choroid in keeping with a high myopic patient. What we see here is vitreoretinal traction with the arrow, presence of epi-retinal membrane causing proliferation of the retinal surface. Inter retinal fluid over the fovea, presence of alter retinoschisis. Inner retinoschisis, and as you compare the red arrow to the green arrow, you do not want to initiate your membrane peeling or the red arrow because this is normal tissue but with retinoschisis on the nerve fiber layer, you do not want to rip where this nerve fiber layer. And of course there’s sub-retinal fluid associated with foveal detachment in the case of myopic maculopathy.
We discussed there’s thinning of the choroid which is associated with high myopia and staphyloma. We can also see this hyper transmission and the reason you have this hyper transmission is because of myopic maculopathy with loss of RPE. And when you have loss of the RPE tissue, then light penetrates better. That also gives you a visual prognostic feature that even after surgery vision will not be 20/20 or close to 20/20 even.
This patient I would have gone bilateral vitrectomy with inner limiting membrane peel from edges of the staphyloma to edge of staphyloma, in this case of high myopia patient. And you can see that what we discussed previously there’s on the fundus picture you can see myopic degeneration with RPE loss. After a month post surgery, there’s residual sub-retinal fluids and schisis. And patient really needs to come in. Instead of repeated the surgery, I injected SF6 gas bubble and our patient face down and after a month patient vision was near baseline. Of course limited presence of RPE while secondary to myopic maculopathy.
It goes to highlight that you’re understanding OCT images. Actually, it not only help you with diagnosis but also predict the visual outcome for patients.
What someone asked is what’s the difference between retinoschisis versus retinal detachment? Schisis is splitting of a layer of retina but the outer retina is still intact. While retinal detachment is the detachment of the entire neuro-sensory retina. The difference clinically is that retinoschisis are usually dome shaped as you can see in this image at the bottom right. And they’re more transparent, less mobile, no corrugation on the surface, and less likely to induce RPE atrophy. And of course, one of the simple way to test it is if you’re concerned about peripheral retinal detachment, a laser uptake indicates that it is retinoschisis because retina is still attached. Laser retinopexy treatment on retinal detachment, there is no uptake because the retina is detached. Much like a wallpaper coming off the wall and if you want to put an in over it, you nail it to the wall itself. Where schisis is still attached to the wall because ultimately it is still attached.
However, the best way to differentiate them if you can is still using OCT. Whereas sub-retinal fluid with retinal detachment looks something like this with detachment, neuro-sensory retina and presence also of sub-retinal fluid and intact RPE here.
This is a patient that was sent for repeat treatment of macular degeneration which she had stopped a few years ago. She had a history of macular degeneration. Received treatments and anti-VEGF treatment was stopped a few years ago. She was referred for intra-retinal fluid and also repeat treatments. You can see that the vitreous cavity is clear, the epi-retinal surface and vitreomacular interface is normal. Intra-retinally you see this sort of cystic look appearing structure with hyper reflective line and hyper reflective lumen, overlaying this sort of area atrophy was retinal fibrosis. What can this be? Do you seek this treatment?
Of course you already know from the picture that this is an area of atrophy with degeneration. What this small structure is the outer retinal tubulation. What outer retinal tubulation is, there is essentially a breakdown of receptor segments. This can happen in any condition that has a chronic macular degenerative process. AMG, Stargadt’s disease, where the RPE is lost. And without the RPE the photoreceptors do not get their proper nutrition and as a result hyper reflective. The outer segment photoreceptor is hydrophoboic just like putting a drop of oil in water, it likes to protect itself and wrap itself into a ring. And therefore forming this outer retinal tubulations. This is different then a retinal cyst which means you don’t treat them even if you repeat in these patients, they will still be there. In fact in the context of a sub-retinal fibrosis , the outer retinal tubulation and the absence in any internal fluid the sub-retinal fluid hemorrhage, you can consider these treatments.
Here’s another interesting case. 77-year-old female presenting with acute persistent paracentral scotoma. Again you see something that’s in the middle part of the macula here. What we see is this hyper reflective band. Of course the vision is 20/40 overall she’s seeing quite well but she complains of paracentral scotoma. A dark shadow right in the center of her left eye. The red arrow labels this hyper reflective band that we see. It is etiologic for a certain condition. Fundus photo you may or may not see this grayish little segment parafoveally. This condition happens in the middle layer of the retina and therefore what do you think this is called? Most of the conditions are similar with these hyper reflective bands occurring in the middle of the retina.
Now if we look back we remember that for cotton wool spots and their fiber ischemia also give you this band, white hyper reflective nerve fiber layer.
This is a condition called paracentral acute middle maculopathy or ischemia of the middle retina. It is usually associated with reduction of the macular capillaries. Mainly in the middle layer and the reason is because capillaries in the middle layer of the retina has the watershed zone. This watershed zone is perfusion rather than infusion from inner/outer retina. When there is foveal ischemia or the increase in blood supply especially with risk factors such as these vasopressors, caffeine, diabetes or vascular disease, you can get these ischemias. Often they can also be associated with central retinal artery occlusion or central retinal vein occlusion.
Another very key way to help you diagnose patients and vision is the use of a very important structure called the IS/OS where the ellipsoid zone. And this zone is important because it hosts, this is the powerhouse of the choroid center and it contains a lot of mitochondria that’s required with photoreceptors. The disturbance of this layer will result in the decrease in vision.
We’ll see in this case a 45-year-old gentleman who came from Barbados, complained that he’s had many years of poor vision. And you can see in OCT there’s bilateral disruption of the outer retinal layer and disruption of the ellipsoid layer causing some transmission with hyper transmission. This photo shows this yellow dot.
What’s your differential diagnosis? Of course the most common one being solar maculopathy. The one that most of us are familiar with. Where someone looked at the sun, either the sun directly, even if you wear your sunglasses. Staring at an eclipse, an eclipse is not safe and can often result in photic maculopathy. And this includes solar maculopathy or even laser maculopathy. Laser pointer-induced maculopathy sometimes. And of course knowing the previous discussion about subfoveal translucency as you can see on the bottom image. This is post VMT macular hole, retinal detachment repair. You can get this sort of outer retinal defect.
And some of the new diagnoses are popper maculopathy where the use of nitrous contents for recreational use. Tamoxifen, pseudo-vitelliform dystrophy. And unilateral acute idiopathic maculopathy or focal fovealitis you can also get this sort of disruption to the layer. However you can really scrutinize the OCT images we will see the subtle difference between the inflammatory part and defect. And defect caused by detachment and vitreomacular function. The sort of involuntary process usually have a little bit of fluff to it, much like your freshly diagnosed laser-induced maculopathy. You get this hyper reflectivity in the subfoveal region. Similarly, this is where with uveitis you get this sign right over your outer retina and that eventually gives you a better diagnosis.
Another good use of the ellipsoid layer where the IS/OS junction is vision prediction. For example this patient presents with confluent diffuse drusen with somewhat hyper reflective RPE. You would imagine that this patient would not see that well. But let’s look at the ellipsoid layer. The ellipsoid layer is intact and therefore the patient’s vision is 20/50, he can still see very well. Especially over the fovea. And here’s another patient with focal geographic atrophy. Vision is not going to be great. You can see there’s hyper transmission results from loss of RPE. Let’s follow the ellipsoid layer. You also see there’s abrupt termination of the ellipsoid layer with loss of RPE. And therefore vision is not great and we expect a counting finger vision.
Let’s move on to the sub-retinal space. We’ll start with a case instead of going over the different images. A 75-year-old Caucasian female referred for dry macular degeneration in both eyes. She’s otherwise healthy, on high blood pressure medication. Vision’s 20/30, she’s not so much disturbed by her vision but our colleague had noticed these yellow flecks over her macula. Similarly on the right eye you also get these sorts of yellow flecks. On autofluorescence, you see these yellow flecks become hypo autofluorescence. And of course we’re going to scrutinize her OCT and what do we see? You see the sort of hyper reflective bumps? Is it above or below the RPE? We can see that these hyper reflective bumps are above RPE. What does this mean? You can call these drusen. But drusen are usually sub-retinal. These are little deposits that’s just laying underneath the ellipsoid layer and above the RPE.
What’s the diagnosis? We are no longer happy or satisfied with the diagnosis which is drusen because that’s just the general term. We need to differentiate is it soft or hard drusen, confluent drusen, large drusen? Is it calcific drusen that can lead to geographic atrophy. Is it your colloidal drusen? Is it your pachy choroid drusen, is it cuticular drusen, is it your reticular pseudodrusen? Of course the answer in this case, like I said, all drusens are sub RPE and in this case the deposit isn’t RPE, it is reticular pseudodrusen.
Why is this important? Because each of the drusen has its own diagnosis and potential implications. For pseudodrusen, much we already discussed. It’s little deposits that lies between RP ellipsoid layer, therefore you can imagine it disrupts the connection with the photoreceptor and leading to atrophy and most commonly type three CNVM, RAP lesions.
An 88-year-old Caucasian female presents with recent blurry vision on the right side with 20/100 vision. On OCT we see that on the right eye there is presence of sub-retinal fluids in the region of macular and the same thing on the retina thickness map. And associated with sub-retinal hyper reflective material. Many of you expressed in learning about angiography. That, in itself, is a big talk. Most useful aspect of OCT angiography is in the context of neovascularization. In this case, we are not 100% certain that the sub-retinal fluid is due to loss of RPE failure. When the RPE becomes defective, you can often get sub-retinal fluid without the absence of choroidal neovascularization.
This is when OCT angiography comes into play. You can see that there is some sort of vascular net and also you can see these red spots. The red spots is full signal meaning these are true full signals in this vascular net. And therefore this is choroidal vascularization at one resulting in presence of sub-retinal fluid. And so this patient warrants anti-VEGF treatments. She received three injections and vision is 20/50 as this membrane just sort of affected her sub-choroidal area. And with repeated injection we can see these vascular net’s shrink in size this resolution of sub-retinal fluids.
However, like we just said, choroidal neovascularization and presence of retinal fluid with imaging modality is now becoming more complicated and dry AMD. As we can see there are non neovascular non-exudative for your dry AMD. I use the Cirrus PAD in this case but of course drusen by PAD will work. Then we have the non neovascular exudative AMD in which case you see no neovascularization or presence of sub-retinal fluid and this is usually due to your RPE failure. So this injection may or may not solve the sub-retinal fluid. In fact, based on the fluid study, sometimes sub-retinal fluids is healthy just like in central serous retinopathy or CSR. Fluid might be protective for these cases as you are too aggressive and due to atrophy and collapse of the RPE layer there.
Then you have your choroidal neovascular membrane with exudative. And this is your wet AMD. And of course there’s presence of neovascular membrane with leakage. This also warrants for investigation.
Other important signs of prognostic features associated with wet AMD includes the onion sign, pre choroidal cleft as you see between the red arrows, neuro degenerative cysts, RPE rip, outer retinal tubulation, and shallow irregular RPE elevation. SIRE or double layer sign.
With time we’ll describe a few. First you may see this sub choroidal neovascularization with presence of fibrovascular PED with this sort of onion sign. You can see the layers of onion. And this basically indicates a chronic exudative process where the layering of cholesterol give you this layering of one pattern. And it’s usually found in type 1 CNV and PCV. Despite repeated anti-VEGF treatment, this layer will be there. But in essence if you see that it means that this patient has choroidal neovascular membrane with presence of cholesterol deposit.
Although in this case we see that there is an OCT of a macula with presence of sub-retinal hyper reflective material. Presence of a choroidal neovascular membrane with onion sign hence what the arrow is pointing at are pre choroidal clef. You can see the choroid and these clefts are in between the RPE membrane and prechoroidal. The significance of this, we wanted to create these clefts, there must be some sort of contraction of fibrosis to do this in the macular membrane. And this contraction causes little focal detachments of your choroidal neovascular membrane or RPE and underlying Bruch’s membrane. What happens is there’s a 50% chance of associated RPE rip and sub-retinal hemorrhage and so you should warn the patient before treatments.
As in this case, this is a patient I saw who presented with neovascularization with this large pre-choroidal cleft. Signaling that there is significant tension neuro fibrosis. And patient received anti-VEGF treatment and of course here’s RPE rip. These slides will give you the prognosis and some of the features that you have to warn patient beforehand so if you see these things happen, it’s happened.
And we have these sort of inter-retinal oval shaped cysts. These are not macular edema because if you look at the retina it’s not swollen. The size of retinal layers seem to be pretty consistent, if not a little atrophic. In the retina thickness map there’s no thickening. These are degenerative cysts usually associated with macular edema or associated with neurodegenerative disease. Sometimes very advanced glaucoma or other neuropathies you can also see these. This would depend on this there’s a lot of edema before treatment will not work.
When we put this all together, we have these sort of retinal pseudo-cysts where it basically don’t warrant any intervention treatments. Outer retinal tubulation on the left, the degenerative cysts in the middle, and also this sort of squarish cavity pattern of macular telangiectasia are retinal cysts that usually does not warrant anti-VEGF treatments. The feature of mac tel, just didn’t have the time to go over it. Also has this key feature. It’s got the pathognomonic high internal limiting membrane draping. You see this very thin layer of inner nuclear membrane. And you have this sort of square, trapezoidal pattern of intra-retinal cystic cavity. These are not fluid but rather neurodegenerative loss of tissues, secondary to macular diagnosis temporally to the fovea.
And finally we enter the choroidal zone. Previously we don’t know too much about the choroid. Now there are various conditions in the choroidal disease. And we’ll briefly discuss a few.
The choroid is a very important structure that contains five different layers. Its function is to supply the retina and modulate support and function. It’s very important and as we can see in the context of high myopic patients, they usually get elongation of their globe. And they go into axial myopia and associated with this is thinning of the choroid as we see another red arrow. And as the choroid and the choriocapillaris gets thinner, then there’s a lack of support in the RPE and eventually into the myopic degeneration.
Another very common condition that sometimes we see associated with high myopic patients with this big bulge, almost like a dome shaped thing that forms within the posterior staphylome.
This is a dome-shaped maculopathy. Its significance is that it’s sometimes associated with sub-retinal fluid similar to CSR but it is part of the treatment if persistent. When we see staphyloma or high myopic patients, you can see this with its resistant area over the fovea. Instead of bulging out like the rest of the staphyloma, the perifoveal area seems to have a little bit of resistance to bulging out a little bit because of the staphyloma. And therefore forming this dome-shaped. And that’s called dome-shaped macula.
Based on what we’ve learned just now, we looked at an 87-year-old male referred for macular degeneration. He’s complaining his vision has been declining over the past five years. When we look we don’t really appreciate a whole lot of drusens. And there’s really no sign of macular degeneration. But rather very tessellated fundus where we can very clearly visualize the choroidal vessels. And the OCT the retinal layers look pretty normal but the significance is the thinning of the choroid in the absence of any pathology. This is a condition that was age-related choroidal atrophy. It is associated with age of course. In the absence of drusen, it is thought to be an age-related choroidal sclerosis. There’s also a lot higher risk of glaucoma and macular degeneration.
CSR is another condition of choroid spectrum disease. And we know one of the feature of central serous is a thick pachychoroid vessel leading to a small serous PED associated with sub-retinal fluid. And of course these brush border patterns of elongated photoreceptor outer segments. These are the features of CSR OCT. And of course on fundus autofluorescence, you can see the strip inside where the fluid drips with gravity forming this hyper reflectivity autofluorescence. This is the smokestack sign and the other ones dots and the diffuse.
Differential diagnosis of CSR as some of you requested, includes choroidal neovascularization, also optic pit. Any time you see sub-retinal fluid, always trace that fluid nasally to make sure there’s no optic pit. And other conditions are malignant hypertension, uveal effusion syndrome, posterior scleritis, and choroidal tumors of various kind.
Here’s a very young patient of five years of age. Asymptomatic referred for a RPE defect over the right eye. Because you can see there’s a little bit of RPE. His vision’s 20/25, he’s not bothered with a tilted disc. In the OCT we see this outpouching of the RPE layer. With an intact retina. And the retina seems to conform to this outpouching. What can this be? What is the diagnosis of this outpouching of this RPE?
This is a condition called choroidal excavation. So we can see excavation into choirid leading to RPE. There are two types. One is non-conforming type where the retina does not conform to the outpouching. Then there’s the conforming type where the outer retina conforms to the outer retina. This condition is associated with CSR and also choroidal neovascularization.
What we see is patient is enlarged and form disease and choroidal neovasculation. Traditionally it was thought that this might be congenital. But recently there are publications that it’s acquired choroidal excavation.
Again this is CSR with presence of sub-retinal fluid and enhanced-depth imaging confirm pachychoroid. Pachychoroid means they’re pachy vessels, the Haller vessels are large and also the choroid is thick. Normally the choroid should be around the thickness of the retina. And in pachychoroid syndrome disease the choroid is much thicker with much larger Haller vessel with an altered choroidal vessels than usual.
This brings us to the new spectrum condition called pachychoroid spectrum disorder. And we have CSR, PCV, and peripapillar pachychoroid syndrome, and also pachydrusen and pachychoroid RPE changes.
These are the different categories or subtypes of pachychoroid spectrum disease. And the thought process behind this is that your enlarged Haller vessels is compressing Sattlers and the choriocapillaris and resulting in RPE changes. That leads to perfusion and small drusens and then CSR and then choroidal neovascularization, PCV, and so on.
We can see these pachy-vessels. As we go by the blue arrow, these are large Haller’s vessel and as it gets larger it compresses the inner or the center of the choriocapillaris. Over time because of the disruption over choriocapillaris, you get RPE defect. And thus believe all the other following conditions.
And of course in the choroid don’t forget about choroidal mass lesions. Hemangiomas, your tumors, your choroidal nevus. And also choroidal calcification and things of that interest.
At the end of the day, we can’t make the confirmed 100% diagnosis in these cases. But certainly if you divide into zones you can significantly narrow down your differential diagnosis. And also it’s very fun to have these images and be able to tell the subtle differences of these on OCT. And of course, if you ask what else do you use in the retina? In addition to OCT, OCT angiography, we have autos, autofluorescence, IVFA, ICQ, and Vscan. And so it’s really a great time that we have access to all these imaging modalities to help us with diagnosis of different conditions.
Some people asked about how do you make diagnosis of retinal dystrophies? Often dystrophies when they present, they already presented with significant atrophy and therefore you will need multimodal imaging. And use the multimodal imaging or use of fluorescence by VFA, OCT, OCT, multifocal ERG and IRG.
Let’s go back to our post lecture quiz and see if any of you can name all the conditions.
Number one, pseudo-hole. Most of you during the pre-lecture quiz already scored quite well. Let’s do this again. Which of the following is pseudo-hole? Yes, the answer is 2. I will finish the next one before we give the answers. The answer is number 2. Which of the following is retinoschisis or contain retinoschisis? The answer is 3. That’s correct.
Let’s go through them. Number 1 is vitreomacular traction leading to full-thickness macular hole with presence of intra-retina cavity. Number 2 is epi-retinal membrane associated with perifoveal thickening and your pseudo-hole. Straight blunt edge. Number 3 is a posterior staphyloma with foveal detachment, full-thickness macular hole. Presence of retinoschisis. And number 4 is your lamellar hole that looked like an anvil with presence of epi-retinal inflammation.
In this picture, due to a time constraint, why don’t I just go over the answer with everyone. The proper description of this is presence of vitreoretinal traction as you can see on this, or follow my cursor here, presence of epi-retinal membrane, and these vertical columns that we discussed are foveal schisis. There’s no intra-retinal fluid in this case so this will be the answer is 5: 1, 2, and 3, without macular edema.
And reticular pseudo-drusen as we discussed, number 1 is cuticular drusen because the drusen is RPE. We can see RP elevations. And this looked like a little skull tooth, it looks like a little tooth. And they’re all uniform, triangular formation, so these are cuticular drusens. 3 is your soft and hard drusens. And then oh, sorry, 3 is your choroidal drusens. 4 is your pachy-drusen, associated pachychoroid. And usually these are isolated drusens. And 5 is your confluent soft drusens.
And this, of course, outpouching of RPE is choroidal excavation. Which is associated with choroidal neovascularization and CSR.
I hope you enjoyed and I did go over time, I apologize. For those who are interested OCTcases and hope you can also contribute your cases. I know there are some questions but just due to time I’ll just answer one or two of them.
Do you recommend subsource specter domain? If you’re looking for detail, whichever image gives you a better details of course is better. There’s also way better imaging modalities now with Silverstone where you can combine all those scanned OCT and be able to drag where you want scan over the out post map. It’s really quite interesting.
Should we avoid intravitreal injection if we see a pre choroidal cleft? If there’s active CNMB or sub-retinal hemorrhage, you still can receive this treatment. But like I said, treatment is not wrong if you alert patient with potential complications. Just like surgery. Just because potential infection, retinal detachment, pain can occur does not mean you don’t proceed with these treatments. Then you have to inform them of the potential prognosis.
Let’s see. How do you treat acute photic maculopathy? I don’t think there’s a proper treatment for acute photic maculopathy. But there are multiple studies that suggest use of steroid. I have a few patients where they were injured by a laser pointer and one very sad case where the patient was a construction worker, he was using a laser leveling device to level some stuff to hang on the wall and the battery is to put in a flashlight. You can imagine you stick the battery in and you’re pointing the laser right in your face. As he’s clicking the battery into place and the laser shone right into his eye. And resulted in focal hyper reflective over the fovea. No treatment’s offered, his visual is 20/20 very sharp vision and he presented 20/60. Over time it still resolved with 20/25 vision. However post photic injuries you can result in CMVM, macular holes intra-retinal membrane so it warrants observations. For really bad ones or really acute, consider steroids. That’s the only thing that’s published. Again, you really need a large concerted in line to do this.
I think that’s pretty much it. I’m sorry I can’t stay very long, I have to attend to clinic. Thanks, Lawrence, again for inviting me for this presentation.
August 19, 2022
2 thoughts on “Lecture: Practical Approach to Retina OCT Interpretation 2022”
I was really great speech and slides . Thank you very mach.
Fantastic presentation!! Loved it!!!