My fear at slowly going blind

I rarely talk about losing my eyesight - I am almost half-blind now - because I'm embarrassed. Which is odd.

Why, after all, should one feel self-conscious about going blind? It's not my fault. And blindness is an unembarrassing disability. In many ways, it's one of the more glamorous handicaps.

There are many much worse things. My limitations are now such that I feel obliged to mention them to people whom I see regularly. I hope they then understand what might otherwise seem like bizarre behaviour. (Falling over, bumping into people and things, failing to recognise close friends and family, feeling my way along the furniture, and so on.) The miniature frustrations are relentless.

Mostly, though, I avoid discussion of "What it's like to go blind". Why? Because I have come to realise how terribly embarrassing it all is. Being British, I hate making a fuss.

I feel rude telling people I am going blind. What are they supposed to say? All they can possibly offer is: "Oh dear. How terrible. You poor chap. I'm dreadfully sorry." Some women do the verbal hugging thing. Men, almost without exception, are mightily embarrassed. It's horrible to watch. The main reason for writing this is to save myself 100 such conversations.

I have a degenerative condition called choroideremia. It is X-linked (that is, carried on the female chromosome, and thus suffered only by males, always inherited from their mothers). There is no serious prospect of a cure. I have lost half my sight over the past 10 to 15 years, and will lose the other half over the next 10 to 15. I am 33. I was diagnosed when I was 11, but was not told by my parents until I was 17. (Should any parent be considering similarly withholding information from a child, I believe such a decision to be misguided, though I understand why it might seem kind.) The effect of the condition is that in the middle of my visual field I have a large " doughnut" (scotoma), in which I can't see anything. It's not black, or even blank; things just don't appear there. If I pass my hand in front of my eyes from right to left, it disappears as it enters the doughnut from the outside, then re-emerges into the hole in the middle, before vanishing again into the other side of the doughnut and finally ending up back on the periphery of my visual left.

It's possible for someone to walk 100 yards towards me from about a 45-degree angle, remaining all the while "behind" the doughnut and thus entirely unseen by me until I crash into them. Over the years, the doughnut spreads out along both its outer and inner edges, until, eventually, there is only doughnut.

At present, the size of the doughnut alters dramatically according to the light. At lunchtime on a clear, but not bright, summer's day (strong light is painfully dazzling), my vision is at its best. In the evening in a gloomy House of Commons corridor, the doughnut probably obscures three-quarters of my visual field. In bars, restaurants, bedrooms and the insides of cupboards and bags, I can see virtually nothing. Also, everything is darker all the time for me than for normal people.

There are other symptoms and consequences. But more important is how it feels: the psychology of advancing darkness. Embarrassment is not really the worst thing; nor are the daily irritations; nor even - I am assured by people who know - is actually losing that last cherished slither of sight.

Fear is the worst thing. I would never normally discuss it - but, as ever, it feels OK to write it down. I worry whether or not I will be able to function professionally. The advice is not to rely on technology, but to learn Braille. The prospect fills me with dread. Having to learn the extra skills needed to function without sight clearly puts one at a disadvantage. Few, if any, affected men in my family have worked beyond 50. And Milton's not exactly reassuring: " ... Who best/Bear his mild yoke, they serve him best, his state/Is kingly. Thousands at his bidding speed/And post o'er Land and Ocean without rest:/They also serve who only stand and wait."

Great. It's a perfect chance to stock up on some stoical Brownie points with the guy in the sky. Thanks, John. The real point is that the practicalities are obstacles to overcome, not demons to fear. The fiend that turns us protoblindies into early-morning sweats is the moment when absolute night falls. Those who have reached that stage insist the reality is far less black than the fear. Unfortunately, the notion is scant comfort.

Because choroideremia is so rare, most fellow-sufferers I know are Americans whom I have met on-line. One of them, Wayne, described the moment in an e-mail:

"A couple of years ago my field was down to no more than five degrees. One morning I went into the bathroom and tried to turn on the light and found it was burned out. When I tried to change the bulb, I found the light was on all the time. I had lost the remaining sight overnight. I soon found the fear of going blind was much worse than the actual fact. I think it's the fear of the unknown that scares us so much

... We can't let the fear of the unknown paralyse us into seclusion. Believe me, life doesn't stop because someone turned off the lights."

I cried when I read that. Partly because I felt so sorry for Wayne; partly because I felt so sorry for myself; but more than anything, because of my raw, infantile fear of the dark.

He actually, literally, went to change the bulb. You've got to smile.

? Siôn Simon is Labour MP for Erdington. He is married with two daughters and lives in London. The full version of this article first appeared in The Spectator.