The Seeing Eye
When we go about our photographic pursuits, whether it be using cameras, choosing cameras, looking at photographs, or whatever, seldom do we give any thought to our own eyes. None of this could happen without them. They are remarkable, dependable senses which superficially resemble a camera in their operation, though if you investigate their inner workings you will be amazed at how different from cameras they really are. Perhaps a little bit more like digital photography (although of course not digital at all) - you cannot discuss the workings of the eye on its own without discussing the workings of a large chunk of your brain as well. As much as a quarter of your brain is devoted to visual processing one way or another, and it is the combination of all of that image processing, starting with a surprisingly poor-quality input from the eyeballs themselves, which produces a totally convincing representation of the outside world as a sensation in your head. Exploration of optical illusions, many of which can be remarkably persistent even in the face of your knowledge that they are producing false information, can demonstrate that your impression of the world is a heavily interpreted version of the optical images that your eye receives.
For myself, I have probably been more conscious of the workings of my eyes than some other people because they have been "off-spec" ever since I was a toddler. Because my father worked for the Kodak he was aware of the issues of colour vision; and knowing that my maternal grandfather was colour-blind, my brother and I were expected to suffer from the same condition. So as soon as I was old enough to give sensible answers I was tried out on the Ishihara test and to nobody's surprise was found to be red-green colour-blind. The genetics of this condition are well known - it is inherited through the female line but only exhibited (with rare exceptions) by males. So it is passed from grandfather to mother to grandson as it duly did in my case. On top of that, I have been extremely short-sighted from childhood, and wore glasses from about the age of six. By the time I was in my early twenties, my short sight was so severe (-10D in the better eye) that I could focus the end of my nose. I have spent my life behind spectacles, or in the last thirty years or so, contact lenses. This has occasional benefits - if you want to work really close up on something you can use the naked eye - but most of the time is a nuisance to be constantly tolerated.
Then we come to the next problem! As we get older, and it happens to almost everybody, the focusing lens inside the eye adjusts less and less as it stiffens up, and we need reading glasses. Of course, this happened to me too, to the point where I had no accommodation (as the focusing mechanism is called) at all. Problem, or opportunity? What is the point of having a non-focusing internal lens being compensated by a non-focusing external lens? Why not omit the external one and replace the internal one with a substitute of the correct focal length?
So that is the discussion that I had firstly with my optician, and then with several eye surgeons. The conclusion was that it's a good plan! The operation is really the same as is given to people who develop cataracts, which are a deterioration of the natural lens which makes it cloudy. Except, I didn't have a cataract, and I did need replacement lenses of very unusual strength.
As I write this, the lens in my left eye was replaced just over a fortnight ago, and in my right eye the day before yesterday. Already I am seeing at least as well as I used to with contact lenses, and for the first time in my life I have something like normal vision. Of course I still need reading glasses, and as yet nobody has come up with any solution to the colour vision problem … I'm not holding my breath.
Leave a Reply.
An occasional and irregular blog, mostly of photographic experimentation and photographic history.
Copyright © 2023 by John Marriage