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OCT enables early detection of glaucoma progression

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WAIKOLOA, Hawaii — OCT can detect changes in retinal nerve fiber layer thickness before visual field abnormalities in glaucoma become apparent, a speaker told colleagues here.

At Hawaiian Eye 2016, Joel S. Schuman, MD, discussed the use of OCT in the early detection and management of glaucoma.

“Structure and function change at the same time when we’re in the range where both can be measured,” Schuman said. “We’re able to measure change very early on, before there’s any abnormality that’s showing up in the visual field. The importance of that is that it is real disease. It’s not just an abnormality that you’re measuring. You’re measuring progression of glaucoma damage, and you can do it even though the patient has a full visual field. We can do this earlier than we could ever do it before.”

Schuman cited a study published in the British Journal of Ophthalmology in which he and colleagues examined the relationship between structure measured by OCT and function measured by visual fields.

“You can see that if the retinal nerve fiber layer is thick, there is not likely to be an abnormality in the visual field until you hit a certain point, which we call the tipping point,” Schuman said.

The tipping point occurs when OCT and visual fields show measurable changes in retinal nerve fiber layer (RNFL) thickness and visual function.

In the study, the tipping point using the Cirrus OCT (Carl Zeiss Meditec) was a mean RNFL of 75.3 µm, Schuman said.

“At about that point is where you should start expecting to see an abnormality in the visual field,” he said.

Schuman also described a “floor effect” at which visual field defects worsen after RNFL thickness stabilizes.

“You reach a point where the nerve fiber layer is very thin and you don’t measure change anymore in the nerve fiber layer, but you can measure change in visual fields,” Schuman said. “So, there is that floor effect for the nerve fiber layer where you’re getting a stable nerve fiber layer reading, but actually things are getting worse and you can measure that with the visual fields.” – by Matt Hasson and Patricia Nale, ELS

Reference:

Schuman JS. OCT for the management of glaucoma. Presented at: Hawaiian Eye; Jan. 16-22, 2016; Waikoloa, Hawaii.

Disclosure: Schuman reports he receives royalties for intellectual property related to OCT owned by Massachusetts Institute of Technology and Massachusetts Eye and Ear Infirmary and licensed to Carl Zeiss Meditec.