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Geographic Atrophy
Video

Identifying and Treating the Progression of Geographic Atrophy

Posted on

Nimesh Patel, MD:

Hi, I am Nimesh Patel. I’m a pediatric and adult retina surgeon at Mass Eye and Ear in Boston Children’s Hospital, part of the Harvard Ophthalmology Program.

Interviewer:

How is geographic atrophy characterized?

Nimesh Patel, MD:

So geographic atrophy has recently undergone some changes in the classification, particularly looking at complete and incomplete loss of the outer retina layers or outer retinal layers and retinal pigmented epithelium. So it’s a little bit technical how those are defined, and they’re usually using an OCT or optical coherence tomography device to be able to look at that. Over time, we’ve started to really tease apart these different layers in the retina, classifying GA by loss in these different areas.

Interviewer:

How does visual acuity at baseline impact progression?

Nimesh Patel, MD:

So there have been some studies looking at progression of GA and what are some of the risk factors. A lot of them have focused particularly on the OCT findings or the fundus imaging findings. There is some data also suggesting that a lower baseline visual acuity or VA will affect progression, but that’s not really able to be determined at the initial time you see a patient. So when you see a patient with low vision or better vision, it’s hard to say at that very moment will they progress because we don’t know how long they’ve been progressing prior.

Interviewer:

Are there any current treatments for geographic atrophy or ways to prevent the onset or progression of geographic atrophy?

Nimesh Patel, MD:

So, currently there’s not a lot of treatments. Our initial treatments are focused mainly on preventing progression of macular degeneration to begin with, and that’s with [inaudible], vitamins, and continued monitoring for things like choroidal neovascularization as well, which can happen in geographic atrophy. In terms of progression, some of those biomarkers we talked about that can predict progression, could be size of the lesion, bilateral virality, or even multi-focalality of the areas of geographic atrophy. So we know that those patients are more likely to progress, but we don’t necessarily have anything in particular that can slow down the progression at this time, that’s FDA approved.

Interviewer:

Are there any biomarkers associated with geographic atrophy? Is this a potential area for emerging treatments?

Nimesh Patel, MD:

So there are exciting areas of treatment and geographic atrophy, particularly in the complement pathway. There have been some genome associated studies looking at, are there any genes associated with macro degeneration or geographic atrophy? Some have shown that in the complement pathway or dysregulation of a complement pathway, those patients may be more prone. And looking at that pathway in particular, there’s a couple treatments in the pipeline currently that focus on inhibition of that pathway and the complement pathway. What that does, is it leads to degradation of the cells and causes an inflammation cascade that eventually leads to cell death. And there are some drugs targeting that specific time point in the cascade where this activation is taking place.

Interviewer:

What are the best ways to test for geographic atrophy and geographic atrophy progression?

Nimesh Patel, MD:

So it’s usually with imaging. Now we’re looking at the OCT, which is really a two-dimensional picture. We can look at it on FOSS and look at it both dimensions, both the axial and the vertical, and look at area of the geographic atrophy. And that’s where we’re looking at. Some other imaging modalities that come with the OCT are near infrared reflectants, as well as the autofluorescence on Autofluorescence. Geographic atrophy is completely dark because there’s no natural fluorescence of the retina, and on infrared, it’s a lighter shade of gray than the rest of the retina. In terms of the OCT itself, you’ll see absence of the outer retina and potentially the RPE as well. Another sign is transmittance of the signal through the choroid as there’s no RP to block the signal. So those are some of the imaging biomarkers that can look for geographic atrophy.

Ideally, what would have in the near future is some way to measure the area automatically. It’d be really nice if you can do an OCT and have a quantitative number of how much area is lost. We don’t really have that exactly on the software available, but I’m sure it’s going to be coming soon. And some of those other things I did talk about predicting progression, those are really retrospective studies that have looked at it. There hasn’t been too many prospective studies looking at exactly what features are predicting progression, but it seems that the ones that are more likely to progress are the ones who have foveal involving geographic atrophy in one eye and extrafoveal atrophy in the other eye.

Interviewer:

What does geographic atrophy look like in a dilated exam?

Nimesh Patel, MD:

Yeah, so in a dilated exam without a photo or an OCT, what you may see is a loss of the retinal pigment epithelial layer. So that’s going to make a window into the choroid. So you may see choroidal vessels, which are thicker than the retinal vessels. You may also see a lighter color as the RPE doesn’t block the signal from the back of the eye. So sometimes the geographic atrophy lesions themselves are more yellow rather than what you would see the normal choroidal picture being orange. So that’s what it can look like on fundoscopy. They’re usually well circumscribed areas, and that’s the term geographic. That’s where it comes from. It’s not really jagged or patchy. It’s usually large circumscribed, delineated areas of loss. They can be multifocal. They don’t have to be continuous with each other. They generally are in the macula and less so in the periphery of the retina.

Interviewer:

How does OCT-A help differentiate geographic atrophy from other diseases with similar clinical features?

Nimesh Patel, MD:

So OCT-A is an emerging technology where we use OCT plus an angiography feature. The nice thing about OCT-A is that it can provide you with depth resolved images and a 2D plain. So you can look at each layer specifically and look at that layer in two dimensions as well, rather than the one dimension you’re seeing on the regular OCT. We can look at deeper into the choreocapillaris where you may see patchy losses there that can maybe predict some of this progression to atrophy. In and of itself, the OCT-A is really not showing you much more probably than the OCT does it this time, and although it may be predicting future loss with changes in the capitalis as well. The one thing that the OCT-A can show you that the OCT doesn’t show you as well, is also in the deeper layers, it can look for cordal on neovascularization of the retina, which can happen in GA.

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