High-Contrast Visual Acuity Test and Optic Neuritis

Robert C. Sergott, MD: Rod, my patients who’ve had optic neuritis are not always happy when they come back to see me. I have them read the eye chart—the chart with the big E, where there’s a bright black letter and a bright background—and they’re 20/25 and 20/20. But they tell me their vision is not right. What are they describing to us?

Rod Foroozan, MD: One of the things we’re so used to in ophthalmology is testing what’s known as high-contrast visual acuity, and that’s just what you described. Our charts are actually computerized now, so it’s a bold black letter on a white background. When I was in training, we had projectors. You couldn’t even alter that. If the projector bulb was a little dim, the contrast was a little worse. But short of that, we were testing high-contrast visual acuity, which is often very good in patients who recover from optic neuritis. The problem is if you ask them: “Hey, if you cover 1 of the other eyes, do you notice a difference?” And they say, “Of course I do.” Things are washed out with the affected eye. Colors are not the same, contrast is not the same. Things look more dim with that eye, and this is 1 of the things that can be overlooked just by assessing high-contrast visual acuity.

Robert C. Sergott, MD: There is excellent work done by Laura Balcer primarily at NYU Langone Health. And Laura has taught us a lot about this. What’s very interesting, too, is that this low-contrast acuity anatomically is localized to the retinal ganglion cells. Someday going forward, as Rod was saying, this boundary between the optic nerve and retina may dissolve as we learn that if you have inflammation of the nerve, there are secondary effects on the retina as well as perhaps secondary effects on the brain. There’s not a firewall here between the structures, and we have to keep thinking about that.

The leading cause of disability in multiple sclerosis is cognitive impairment, and I think that in the future, all of us—neurologists, ophthalmologists, neuro-ophthalmologists—need to start measuring cognitive improvement and cognitive impairment rather on optic neuritis patients early in their course. If they have problems, then we need to follow that, because it’s such a stealth disease that you can have progression without relapses. We have to make this a multidimensional approach with the help of MS [multiple sclerosis] specialists, with the help of specialists in neuropsychological testing for cognitive impairment.