Lecture: A Practical Approach to Retina OCT Interpretation

Objectives of this presentation are:

  1. Appreciate the advancement in optical coherence tomography technology
  2. Able to identify normal retina OCT
  3. Able to interpret retina OCT with a systematic approach
  4. Able to identify location of vitreo-Retinal pathology based on OCT

Lecturers: Dr. Wai-Ching Lam & Dr. Peng Yan, University of Hong Kong and University of Toronto


(To translate please select your language to the right of this page)

DR LAM: Just a reminder. OCT is using light to create a cross sectional image of the retina. So you get a picture like here. This is an OCT picture, and this is a histology of the macula. So it’s very easy for us to look at the images to interpret the different structures in the retina. I’m gonna skip the… So there are different features on the OCT machine to allow you to look at the images and compare them from time to time. And it also has this normative value, so that you can actually look at it, and know if certain measurements — such as the thickness of the retina — is different from the general population’s. Whether it’s too thick or too thin. So when you look at a picture, like the macular map, then the green is within the normal range, and the red is usually indicating the measurement is abnormal. So we can look at the cross section from the vitreous, from the vitreous, and all the way down to the retina. The vitreous can be something within the vitreous. Like in this case, like the calcium deposit or the atherosclerosis. And you can also see a dense hyaloid, with blood. And you can see sometimes the vitreous is trying to pull away, and the entire hyaloid can be seen on the images. You can actually follow sequentially how vitreomacular tractions can cause a macular hole, like the example here. Vitreomacular adhesion — tractions are when there are some structural changes in the retina. So the traction can cause splitting of the retinal layer, depending on how severe is the tractions. And then we look at how epiretinal membrane changes the structures of the macula. And then we talk about the pseudomacular hole. And the lamellar macular hole, and how to make the distinction. So this is a partial thickness macular hole, with splitting of the retinal layer. So that is a lamellar macular hole, or partial thickness macular hole. So don’t worry about — there was a misspelling there. So this is a pseudomacular hole. When there is actually no macular hole at all, but you get distortions of the macula, creating a vertical shape of the edges of the fovea. Here are more examples of the same. It’s caused usually by the presence of epiretinal membrane. And lamellar holes are typically like this, with significant thinning of the macula, with splitting of the retinal layer. So there are more examples of them. Some of it looks very odd. Very strange appearances. And more examples of lamellar macular hole and pseudomacular hole. So we will then talk about the classifications of macular holes. And how it contrasts with the OCT features. So Dr. Gass described a stage 1a macular hole, where there are these foveal pseudocystic changes, which clinically looks like a yellow spot, but there’s actually no macular hole. And some people call that an impending macular hole. And the OCT shows vitreomacular tractions, with what we call pseudocyst formations. And stage 1b is when the traction is more severe, and you get more cystic separations of the macula. Still no hole. Because you can see the top still intact. Although it is possible the hole can form. If this keeps pulling more. In fact, that’s what might have happened, is that if this pulse more, then you actually get a full thickness macular hole, either stage 2 or stage 3 macular hole. And by this time, it’s not like the hole will close by itself. But before that, when the vitreous separates, without tearing the retina, this might go away by itself. It might get better by itself. And then you have descriptions of a stage 3 macular hole, where there is still vitreous attached to the surface, but you have a full thickness macular hole. When the vitreous pulls away, you get this stage 4 macular hole, with a small pseudo-operculum, lying in front of the macular hole. And the holes usually are quite big. They’re usually about 400 microns in size. So the new classifications of the macular hole, according to OCT, are done much more simply. You describe them as small, medium, and large. That’s it. And these are some of the examples of the holes. We no longer classify it as stage 1, 2, 3, 4. You have to understand: Most of the reasons that we make classifications is because it allows us to predict prognosis and plan management. So in the OCT machine, you can use rulers to actually measure. When you measure, there are two places you can measure. You can measure the narrowest part or the widest part. And the measurement that… So you should measure these portions of the — on the OCT — to estimate whether it is small or large. You see the reason why they classify them, according to the size, because it predicts how well they do with treatment. So the original Gass classification for the stage 1, which is not a hole, we now call it vitreomacular tractions — half of them will get better by themselves. So, remember, the new classification, according to OCT — there’s no stage 1. Stage 1 is vitreomacular traction, so vitreomacular adhesions. And then, depending on the size of the hole, for a small hole, you could treat it with surgery, or you can treat it with just injections. The options of the injections are either an enzyme — in this case, it’s ocriplasmin — or even just a gas bubble. And with a small hole, there is a good chance the hole can close. Both the enzyme and the gas work by creating a vitreous separation. Therefore it’s important to know that the vitreomacular traction has to be less than 1.5… Sorry, 1500 microns. 1.5 centimeters. Millimeters, sorry. So small hole, small tractions. Then you don’t have to have surgery. Otherwise, the other ones need surgery. Okay? So that’s the newer OCT classifications. And we all know: When you have surgery, the success rate is quite good. It’s over a 90% closure rate. Especially if you do vitrectomy, plus peeling the internal limiting membranes. Still, some of the cases doesn’t close. Although it’s less than 10%. And those are the example of those cases, that doesn’t close. Either the hole is quite large — in fact, more than 400 microns in size — or it’s been there for a long time. A traumatic macular hole will have a harder time to close than an idiopathic macular hole. Or if it’s associated with chronic — sorry. Or if it’s associated with myopic degenerations. I’m gonna give you some examples of OCT features that kind of help you to appreciate some of the changes. So this case is a patient with a myelinated nerve fiber layer. So where do you think the changes is going to happen? Okay. So in this picture, where the changes are — which layer of the retina you think the change will be there? So it will be in the nerve fiber layer, where there’s increased thickness, compared to the normal portions of it. You have to understand: This image is taken of the macula. So the retina there is usually thinner, and it doesn’t have that kind of macular contour. That’s why it looks like a very thin retina. That’s the case. And this area is thicker. What is this? I’m gonna go to the back. What do you think that is? So cotton wool spot. So it’s affecting the nerve fiber layer. But it is affecting a very large area of the nerve fiber layer. And it causes some shadow underneath this, blocking the light from coming in. If you saw that whitish area, so the light kind of gets through. So cotton wool spot is the swelling of the nerve material that gets disrupted. So what is this?

>> A swollen nerve fiber…

DR LAM: Right. So it’s a retinal arterial occlusion, with swelling of the retina. Yeah. So there’s a small cholesterol… So it is at the bifurcations of that branching arterial area, and causal retinal edema and a cherry red spot. And the swelling involves almost the entire inner retinal layer. Because the blood supply for the retina comes from the retinal layer. And the outer layer is getting blood from the — circulation from the choroid. That’s why the outer layer is a little bit better looking than the inner layer. And we’re gonna talk about macular edema and the different appearances of it. And they can be various different shapes, depending on how the fluid is being accumulated, within the retinal layer. And this picture also shows a wrinkled posterior hyaloid face with partial vitreous separations. And when you have macular edema, you can have this exudate that is there. And you can see that in the OCT as collections of these crumbs of materials. Some of them can be fairly large, and some of them can be small. So those are the exudate. And there are more examples of exudate, but… What about this one? Anybody know what this is? She didn’t want to share that with you in Vietnamese. So you want to give the answer? So I think there’s a little bit more than the retinoschisis. We’ll go through that. So retinoschisis, as was suggested, can be — basically is the splitting of the retinal layer. Typically, you have these strands of tissue that are still there. And that’s how you recognize it. So the retinas still are not separated, but split. And sometimes you can see some tractions there. And depending on the layer where the split happens, it can be the inner retinoschisis or outer retinoschisis. Do you know when you see the inner retinoschisis? When do you see inner retinoschisis? When do you see inner retinoschisis? In cases of… You can have splitting in the very superficial layer or very outer layer. Right? So in the inner layer, usually you see it in the juvenile retinoschisis. In congenital cases. And the outer retinoschisis you see in aging. Kind of degenerative, senile retinoschisis. So it is important to distinguish between retinoschisis and retinal detachment. We all kind of understand that this looks like retinoschisis, because the retina is more transparent. They don’t usually move. And they are not associated with any scarring. Compared to a retinal detachment, where you can have some scars. When you use OCT, it’s much easier to make the distinctions. So that is a retinal detachment, when the neurosensory retina separates from the RPE. And that’s a retinal detachment. When the neurosensory retina separates from the RPE. And you can have everything in the same eye. That is an inner retinoschisis. That is an outer retinoschisis. And you also have a retinal detachment, where the retina has separated. And that can be seen in myopic degeneration, myopic maculoschisis, with detachment. So now, back to that question. The first pictures. So yes, that is a schisis. So now you know that it’s more than just schisis. Because you can describe it. That is… There’s also a lamellar macular hole. There’s also splitting. Splitting of the retinal layer. And this is an inner retinoschisis, because you can see the outer retina is not involved. So the full answer for that picture will be: Inner retinoschisis and lamellar macular hole. And we also load the layer — this line here is called the IS/OS junction. Basically it is an abbreviation for the inner segment and outer segment of the photoreceptors. But Rick Speight thought that this line, the IS/OS junction, actually represents the ellipsoid area of the photoreceptors. So you see in some of the publications a report that people would describe an ellipsoid zone or IS/OS junction. They’re talking about the same line, where the photoreceptors or the outer segment of the photoreceptors, is present. I will explain to you later on why it’s important to recognize this area. So here is a picture of a patient with right and left eye, with the disruptions of the IS/OS junctions, and the outer segment of the fovea. What do you think this is? Go ahead. Trauma. So it is a form of trauma. So it is a solar maculopathy. It is from the sun. Damage to the outer segment of the photoreceptors. And you can see the arrow pointing at the area of the disruptions. Now people have recognized the OCT features of the solar maculopathy. This is when people look at sun and get sun damage to the fovea. And the damage is concentrated in the outer segment. What about this case? Where there is also another disruption of the IS/OS junction or ellipsoid zone? And it’s only on this eye. The other eye is normal. And the person never looked at the sun. So it’s also trauma, but a different kind of trauma. So the patient has a macular hole, and had surgery to close the macular hole. So even when the hole is closed, the vision doesn’t always come back good. It’s because there is a disruption of the IS/OS junction or the photoreceptors. So, looking at the picture, this is a lot better than before. But the vision stays about 20/100, 20/70. Never improves after the surgery. This is the case where the doctor is happy. The patient is not happy at all. But at least you can explain to the patient why the vision is not getting better after the surgery. Because the photoreceptor never completely comes together and repairs itself. So this is a patient with age-related macular degenerations, with this scar in the macula. What is this one? This is another similar patient, having the same kind of scar. And there’s another patient, of the same thing. So there’s the clinical pictures. You can see the age-related macular degeneration, and this is the change, and this is also the change. Are they the same thing? Or are they representing different things? And what is it? Any idea? The green one might be new blood vessels. So this is a feature that people recognize more now. It’s called outer retinal tubulations. So what is outer retinal tubulations? You can see them in these areas. And they are different from the cystic changes in cystoid macular edema. It’s caused by the retinal degeneration, when the retina kind of reformed itself in the little tubes. So those are the little tubes that you have. Looks like blood vessels, but they are not blood vessels. They are actually retinal tissues, photo receptors, that get kind of — reorganize themselves. And you see that in chronic retinal degenerations. In macular degenerations, in the advanced form of macular degenerations… And also in retinal dystrophies. Like retinal degenerations. So there are some mores examples of it. This happened to be a cut on the surface. So you can see… Oops. You can see here is the clinical pictures of the area of retinal degeneration, some macular degeneration. You can see the tubes get cut on this scan. And those are cut cross sectionally. So going back to this picture, the green one is the outer retinal tubulations. The red circle are just cystic fluid in the retina from macular degenerations. So when we look at the choroid area, you can see drusens. You can see in here… Those are hard drusens or calcific drusens. And these are soft drusens. And this is a pigment epithelial detachment. So this is actually a kind of polyp lesion. Polyp. A PCB. So you can see… Just looking at the appearances, you can tell the difference between the features of them. And here is an example of a central serous choroidopathy, where you have serous detachments of the retina. The photoreceptors are pulled away from the RPE. And typically you have a small pigment epithelial detachment. And they leak fluid. So the differential diagnosis of this subretinal fluid can be either from what we just showed you — central serous or the optic nerve pit, or even from scleral inflammations. And they’re all exudative retinal detachment. Here’s — and I’m sorry. They got cut off. But here you have another example. So what do you think this one is? With the list of differentials I just showed you, which case do you think it belongs to? Any ideas? Okay. So what is interesting is that you have schisis, and different layers of schisis. You have the inner retinoschisis, involving the inner retinal layer, and the outer retinoschisis, involving the outer plexiform layer, and it also has a focal retinal detachment. And you can see it in the different layers. So you can see clinically there is a small optic nerve pit in a 12-year-old boy. So I just want to emphasize to you that when you look on OCT, you should not forget there’s a patient to look at. Because the OCT doesn’t help you very much. But if you look at the patient, and look at the OCT, then you’ll know pretty quickly what’s happening. Don’t forget to look at either the patient or the fundus photograph to get a better idea. So the patient underwent surgery, a vitrectomy and a posterior vitreous separation with gas injections. And you can see the subretinal fluid went away, and so the schisis changes went away. With improvement of the vision. The vision gets better. Okay. So… What is this one? Any idea what it is? Is it… A pigment… Anybody who thinks it’s a pigment epithelial detachment? No? Okay. Who thinks this is a cystoid macular edema? No? All right. So you’re all right. So it is not a pigment epithelial detachment. It is not… In fact, if you look, there are little changes elsewhere in the retina. Not just in the fovea. And if you look at the pictures, you can actually see them. So you can see them on the clinical pictures. That you get little bubbles. So they are subretinal perfluorocarbon bubbles. And they have very special features that you can recognize by just looking at it. Oops. People describe this as omega sign. And the reason for that is: These bubbles of perfluorocarbon fluid cast a shadow into the tissue underneath it. And create this part of the omega symbol. It is because the perfluorocarbon fluid has a different light reflection than water. It also stretches the tissue around it, making the tissue next to it a little bit — slightly more dense. So, fortunately, right next to it, you have this cystic swelling. You can see there’s no shadow. It’s not perfectly round. So it’s a pocket of fluid from, like, inflammation, from CME, that collected within the retinal layer. So this is an omega sign, and this is not an omega sign. So what about this one? Is this another pigment epithelial detachment? Or is it a drusen? So how many people think it’s A? How many think it’s B? How many people think it’s a choroidal neovascular membrane, C? And how many people think it’s D? So, I mean, everybody… I didn’t see a single hand. So either you are not committing, or you don’t think any of these answers is the right answer. And I see that not everybody is sleeping. There’s only one person sleeping. So this is the picture of the patient. We can see this yellow-orange material in the macula. And when you do the fluorescein angiogram, there’s no hyperfluorescence that you will see in either a pigment detachment or a CMVM. So this is what we call an adult vitelliform maculopathy, where this kind of lipid-protein material accumulates. They accumulate on the undersurface of the RPE and the choroid area. It’s important to recognize this, because you do not give them intravitreal Avastin. Because it doesn’t change it. And this patient just needs to be followed. And this was described a long time back. I’m just gonna give you the pictures or the comparisons between how to recognize them. Usually they are younger patients. Because age-related macular degeneration — usually 55 or older. They’re usually younger. And the vision is usually better than the macular degeneration patients. The vision. And if you have the way to test them, they have abnormal EOGs. And for the adults, they don’t have any genetic predispositions. And for the Best’s disease, the vitelliform dystrophy, they tend to be autosomal dominant. So these are some of the examples of the pictures of the adult vitelliform maculopathy, with autofluorescence showing abnormal autofluorescence in the macular area. And then you can see the OCT features. In this case, the vitelliform material, the lipofuscin material, fills up the entire space there, as you can see on the fluorescein angiogram. And they can be hypofluorescent. And they won’t get better with Avastin injections. So this is another case of a geographic atrophy of macular degenerations. And you can see the clinical photograph where the geographic atrophy is. You can see the choroid, choroidal vessels. Because the RPE and choriocapillaris is gone. And on the OCT, you can see the same thing. You see the missing RPE and the missing choriocapillaris. And because of their absence, you can see the light can come through, creating these artifacts. So for age-related macular degenerations, you can look at some of those features. On here, you get the choroidal neovascular membrane. You get these cystic changes in the intraretina, you get blood underneath the retina. And you can have drusens, and you can have this choroidal neovascular membrane. And what’s good is that you can see all those changes on OCT. So you can see the subretinal hemorrhages. You can see the intraretinal fluid. And I’m gonna show you even the better pictures. So you can see the correspondence between the cartoon and the OCT pictures. So that looks pretty convincing, for the changes you see. You see the subretinal fluid. You can see this area of pigment epithelial detachment, you can see this choroidal neovascular membrane with blood. Here’s another example, where you can see this blood, sticking to the undersurface of the retina. You can see intraretinal fluid. You can see the choroidal neovascular membrane with blood, and the pigment epithelial detachment. Okay. So… This picture here… I can tell you a patient with macular degenerations was getting treatment with Avastin, and comes back to you, and the follow-up, and this is what you see. What do you think happened? Any ideas? So is it just, say, pigment epithelial retinal detachment? How many of you think it’s a pigment epithelial detachment? No hands. A disciform submacular fibrosis? A choroidal neovascular membrane? Thank you. There’s one hand went up. And a pigment epithelial tear? Two hands went up. Three hands went up. Good. So… So this is the pictures of the patients before getting treatment for Avastin. So you can see the fluorescein angiogram showing a pigment epithelial detachment. You can also see on OCT there’s a pigment epithelial detachment and cystic changes within the retina. So there’s before the treatment. This is after the treatment. You can see the RPE gets disrupted. An RPE tear is a complication of treatment with either anti-VEGF or laser, or even nothing. It can happen as a complication of macular degenerations. So let’s go back to that picture. You can actually see… This is the RPE layer. And it’s broken. And actually the RPE scroll, curved in.So when an RPE tear happens, the RPE will rip and kind of curve. And when you look at the clinical picture, it’s actually quite easy to appreciate. So this was the pigment epithelial detachment. And it ripped. And so the RPE here curved up and leaving this area here without any RPE… And that’s why you have this area of hyperfluorescence, because the RPE has pulled away. And this hypofluorescence, because there’s more than one layer of RPE that’s block the fluorescein. It doesn’t always have to have bad vision. If the fovea is in here, within the area of the RPE still remained, even though there is a redundant RPE, the vision is fine, because the RPE is still supporting the photoreceptors. And if the fovea is here, then it’s not good. That would be the same as an area of geographic atrophy, where there’s no RPE, and the photoreceptor will slowly degenerate. For this patient, the fovea is here, so his vision actually is not affected by this complication. I guess not as yet, until he has other problems. So here’s another example. When you have such a large pigment epithelial detachment, they are more prone to form an RPE tear. Doesn’t matter what you do. Whether you inject, you laser, or you do nothing. It can happen. So in this case, the rip actually happened in both the top and the bottom of the RPE. And basically it ripped on the superior pole and it also ripped in the inferior pole, and you have redundant RPE here. And you can see the RPE layer here is extra thickened. So now another patient. Vision is very good. 20/25 and 20/20. And this is what you see on the OCT. So… Any idea what it is? So of course the changes are in the right eye, where this funny-looking thing is. So this is what we call a focal choroidal excavation. This paper is in 2011. So it’s about six years ago now. So they describe whether this excavation is… Whether the retina also follows the excavation, where it’s called conforming, or it doesn’t follow the excavation. It stays on top, with fluid in between. It’s called non-conforming. I’m just gonna go back to these pictures. You can see this eye is a little bit myopic, because there is these staphylomatous changes. This curving out. So this one is the same. So what you see here is an exaggerated or very focal area of staphyloma, basically. And the paper describes several different cases, and usually they are not a problem, whether they’re conforming or non-conforming. But in some of the cases, for instance, the case that they describe, they can form a choroidal neovascular membrane that can be seen on fluorescein angiogram. And this patient was treated with anti-VEGF to dry that up. Because there was this subretinal fluid that occurred from the leakage of the choroidal neovascular membrane. And there’s also the incident where you’ve seen bilateral focal choroidal excavations. There’s also a very strong association with the presence of central serous choroidopathy. CSR. So when you see a focal choroidal excavation, it is not completely benign. You need to think of the possibility that it could be choroidal neovascular membrane association. It also could associate with central serous. Otherwise, we can just follow them. And here are some of the choroidal lesions that you can see. This one here is a choroidal hemangioma. And here is a choroidal melanoma. You can see the consistency of the choroid is different from hemangioma lesions, from melanoma lesions. And on top of that, the melanoma lesion has much abnormal RPE layer than the hemangioma lesions. And sometimes they are seen with associations of subretinal fluid, in the case of hemangioma. Or any ocular tumor can be seen with subretinal fluid. They can cause exudative retinal detachment. Okay. So here’s a patient. There’s some bad color here, but this is the fluorescein angiogram. Anybody have any idea what is this? The patient has some chronic visual losses. No? So does this help? This is autofluorescence. So this is an example of a bull’s eye maculopathy. The patient’s been on hydroxychloroquine for a long time, for treatments of rheumatoid arthritis. So this is a normal OCT. And this is a normal multifocal EROG. So each one of these little ones is the EROG wave forms. And the center part is more sensitive. That’s why it has more response there. So this is one for the bull’s eye maculopathy. You can see that there’s a ring of abnormal EROG. You see this here. The waveform is much smaller. You can get a central scotoma. And you can see here and here you have this thinning of the outer nuclear layer. The photoreceptors got damaged there. So this is corresponding to the ring of diminished ERG response. So you can see these shapes of changes. So they describe this as “flying saucer”. Like the Alien. I should put a picture for that one. The UFO? Yes. So if you have some imagination, this is a spaceship from Mars. And I don’t know, in terms of the time — should I stop? Okay. All right. So I have given you a little bit of the features of PCV on the OCT before. On some of the examples. So I’m gonna go a little bit more describing PCV on OCT. Because these days you can actually make your diagnosis of PCV on OCT without the ICG help. So we’re gonna highlight some of the features. So instead of reading this for you, I’m gonna use an example to show you those four features. Okay. So they usually have this peak pigment epithelial detachment. So like a little mountain. Rather than just a dome. Or the normal pigment epithelial detachment. You also see this double layer sign. These two lines. Double layer sign. That usually correspond to what we call the branching vascular network of PCV. Okay? So this is what I was talking about. The branching vascular network. And that is seen in about half of the patients with PCV. So the other thing is the choroid is usually thicker. So here’s another example of a suspected PCV lesion. This is a pigment epithelial detachment. But you can see this notched pigment epithelial detachment. And in the game there’s another notch here. Notch. Like, not smooth. A little bump. And the reason why you have this is — that’s usually where the polyps may be located. Therefore it changes the normal contour of a smooth dome into these kind of irregular shapes. So there’s this double layer sign. You can see this one layer and two layer — that usually represents these abnormal blood vessels that are seen — branching blood vessels — that are seen associated with the polyps. And the pigment epithelial detachments usually are not clear fluid, because they have blood in it. So they have hemorrhagic pigment epithelial detachment. And the choroid can be thicker than normal. And so in fact… People actually look at using OCT, compared to the diagnosis, and found them… If you have those features, you have a very good sensitivity and specificity to diagnose PCV. So next time when you see these features, and the double layer sign, and the increased choroid thickness, think of PCV. It would be nice if you can do an ICG to confirm it. But if you don’t have ICG, you can still think of PCV being very high in the diagnosis. The reason why we need to know is the treatment for PCV is different than treatment for age-related macular degenerations. Because you need to treat the polyps, in addition to treating the abnormal choroidal vessels. If you just inject anti-VEGF, it doesn’t completely get rid of the problems. The injections of anti-VEGF helps the choroidal vessel. But it doesn’t get rid of the polyps. So the patients still have the risk of having the problem coming back, or even worse, may have the polyp rupture and cause a large hemorrhage. So you need to treat the polyps with either laser or photodynamic therapy. In addition to the anti-VEGF. On top of the use of anti-VEGF. So that’s why making the diagnosis is important.

June 1, 2017

Last Updated: October 31, 2022

1 thought on “Lecture: A Practical Approach to Retina OCT Interpretation”

  1. Good lecture on Oct of retina and example in between lecture improve the scale of managment retinal disorder by coming vitroetinal surgeon. Thanks sir to help us clear the concept of rental disorder (Oct finding.)


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