IT'S NOT A TUMAH
I've been whining to quite a lot of people about my vision over the last year. If you've been wondering what's up with that, read on. Most other people should stop now.
Over the last 18-24 months my vision has massively deteriorated. A slight extra glow to streetlights at the end of a long night was my first indicator -- rather like the glow you get when it's a bit foggy. This slowly became a glowing halo around all lights at night, then lights during the day, and now anything light-coloured. Light text on a dark background -- the default terminal screen in a UNIX environment -- is completely unreadable to me; I have to change to a lower-contrast colour scheme. Credit sequences in movies are similarly unreadable, and dark scenes in general are becoming harder and harder. At night, my vision has become an increasingly indistinguishable mess of overlapping, glowing blobs which has significantly decreased my enthusiasm for going out at night.
I have obviously been trying very hard to work out what is going wrong. A succession of opticians have examined my eyes and found them completely healthy in every way they can measure -- my prescription remains the same: in bright light, everything is perfectly clear. The pressure inside the eyes, the pattern of tear distribution, the surfaces of my corneas and my retinas are all healthy and unchanged. Listening to my symptoms they pronounced "dry eyes", and so a succession of eye drops, gels, heat packs and oil pills have been tried, all to no apparent effect.
As the deterioration continued unchecked, I began to press my opticians to try harder. This led to further tests, all still good, and questions, aimed -- subtly -- at determining whether there might be a neurological cause, i.e. something like a brain tumor. Finally, yesterday, I got an answer: "spherical aberration". A very precise map of the surfaces of my eyes show that they are microscopically flattened at the front. This type of flattening used to be a common side effect of lasik surgery, and in fact it was a lasik clinic where I got the tests done.
This answer, while heartening -- the lack of any other probable cause had me really quite worried about the tumor option -- is also very dissatisfactory. There is no treatment for having flat eyes. You apparently just "get used to it". The other odd factor is the sudden onset -- your eyes are either flat or they aren't; they aren't supposed to suddenly get flat, or at least not this quickly. The lasik doctor said, however, that eyes do change shape in your mid-twenties, so it was not entirely unheard of.
While unsatisfactory, I guess this explanation will have to do. At least there is something they can point at, and I will keep -- ha -- an eye on the situation.