In the Dark

One of the things I managed to squeeze in during these last hectic days was a visit to the optician. I hadn’t had my eyes tested since I lived in Brighton, probably more than five years ago, which is a bit long to leave it for one of my advanced years. Inevitably the test revealed that I needed new spectacles, though curiously one eye – the left – has changed much more than the other since my last test. My prescription has corrections for both astigmatism and myopia (short-sightedness) but these are both well corrected by varifocals, the type of glasses I have worn for some time. My new specs took just a week to arrive and I find reading much more comfortable wearing them than I did with my old ones.

I remember the first time I had to wear varifocals I found it quite difficult, especially looking down through the bottom half of the lens (which is where you are assumed to be looking when reading) as they make it difficult to judge the distance to the ground (or, more dangerously, exactly where the next stair is….). I found after a day or two I was used to the varying focus and now I think nothing of it.

Because it means that your eyes focus differently on horizontal and vertical lines, and that’s exactly how text is constructed, uncorrected astigmatism makes it difficult to read words and numbers at a distance. With varifocals you have to look through the top half of the lens, which is the bit that corrects the astigmatism, and move your point of view until you find the place where the optical performance is best. I’ve often found myself in the audience of a lecture moving my head in odd ways to try to find the best angle to read what’s on the screen. I hope it’s not too disconcerting for the speaker when I do that!

The most interesting bit of my visit to the optician however was that I had an optical coherence tomography scan which generate a three-dimensional picture of the back of the eyeball. I’ve never seen one of those before. Here’s an example (not me):

This type of scan can be used to diagnose things like glaucoma and diabetic retinopathy, neither of which I have. In my case though it did reveal a significant level of unevenness in the surface at the back of both eyes and some signs of swelling of or near the optic nerves. The optician showed me the scan and pointed out these abnormalities, but said that it wasn’t anything too worry too much about as he thought it was historical rather than progressive. He said the only time he’d seen anything like that was in the cases of people who had in the past had some form of trauma to the head (which can cause increased pressure inside and so damage the back of the eyes).

I’ve blogged before about the long term effects on my mental health of the beating I experienced in Brighton over thirty years ago, but this was the first time I’ve seen such clear evidence of the physical damage that I presume was caused by that event. In extreme cases I experience periods of exaggeratedly heightened awareness of things moving in my peripheral vision that I can’t keep track of, accompanied by auditory and visual hallucinations. I’m not an expert but it seems likely to me that what the scan revealed may play a role in these episodes. It doesn’t explain why they seem to be triggered by stress, though, so there must be other factors.

Over the years a number of people have remarked that I often have the blinds closed in my office during the day, and that as well as that as well as being varifocals the lenses I wear in my glasses are reaction lenses (i.e. they go dark in bright light). Avoiding bright light in such ways was suggested by an optician some years ago, who suspected I might have some form of retinal damage but couldn’t see anything definitive with the technology available then. It seems he was right!