As hypothetical conversations go, this one was fairly portentous. It was a month before Christmas and, as I planned on being away over the holiday, I had arranged to meet my younger brother for an early celebration in a Glasgow pub. We were doing the sibling thing, recounting embarrassing stories from each other's past, and the story about his time in the army came up - again. He had struggled during night exercises due to difficulty seeing in the dark, often running into trees and amusing his comrades in the process. They couldn't understand his failure to spot an obstacle as big and apparently
obvious as a fully grown tree.

It was of interest to me because I too struggled to see in the dark. Laughing at him allowed me to laugh at myself, about what was in fact a frustrating - and sometimes painful - problem.

We went on to discuss whether we would rather go blind or deaf, were we forced to choose. I love to read, so said I would prefer to keep my vision; he cited his love of music as the reason he would rather sacrifice his sight to keep his hearing. "Plus, at least if you're blind you get a free dog," he reasoned. I didn't buy a free dog as being compensation for the loss of my sight when he said it, and I still don't. Particularly because, in the five years since that conversation, I've discovered that my brother and I share a genetic condition that is, over time, leading us both into blindness. I haven't received my free dog yet, although I do have a rather friendly white cane, and at least I don't need to pick up its poo.

I became vaguely aware that there was a problem at the age of 14. It was the first day of my paper round, around 5.30 in the morning in the dead of winter. It was cold and dark, and I was standing at the bottom of some steps leading up to one of the houses on my round. I knew they were there, but realised as I approached them that I couldn't see a single step and had only a vague sense of where the door was. In the end, I reached the top in the same way I would for the rest of the winter - by scrambling up the steps on all fours.

It was more than 10 years before I realised that there was something significant about my inability to see in the dark, and another four before I finally pinned down a doctor long enough to learn that I have a degenerative eye condition called retinitis pigmentosa (RP), the result of a genetic mutation that affects around 20,000 people in the UK and around 2 million people worldwide. Its progression causes night blindness, damages the peripheral vision and eventually leads to complete loss of sight. There is no treatment and, for me at least, no timescale for how quickly my eyes will degenerate.

People usually refer to it as "tunnel vision". That is about the best description there is, but it fails to truly convey the extent of the problem. There are points in my peripheral vision that simply let me down and others that don't. In particular, I struggle to see when I'm tired,I often trip over things and regularly fail to notice people until I'm on top of them. As I recently found out while taking part in a football match organised by workmates, I struggle to keep track of things that are moving at any speed, including the ball and the other players on the pitch. They wisely kept me on the subs bench until the end of the second half.

Getting the diagnosis was a mission in itself. Having first raised my concerns with an optician at the age of 20 - "bit of night blindness, one of those things," he said - it took a further seven years to get an optician to finally refer me to the eye hospital and, even then, it was only after an exercise to test my field of vision showed a result that was so disastrous, the assistant in the shop became convinced that his machine was broken.

The specialists at the eye hospital did little to explain my condition - a job that ultimately fell to my former partner, Dawn, who had done her own research. To date, I've had next to no information about my condition from specialists, and have instead endured countless eye examinations and bizarre andinappropriate questions with no context. I've been asked about my marital status, whether I plan to marry and whether my parents are cousins - sadly the riposte "no, they're brother and sister" came to me too late.

I've received no support from the NHS in adapting practically to my situation, but have been offered genetic counselling to determine the chances of passing on the condition to any children I might have. This is perhaps useful for some people, but I would really like to know how to go about arranging my kitchen in a way that will make it possible for me to continue eating in the future.

Dawn and I split up at the start of this year when she relocated for work, but we remain close. She has always been, and remains, incredibly supportive, but I still wonder whether things are easier on her now that she no longer has to constantly look out for me.

I recently asked her whether she preferred being in a relationship with someone who could see. I was always conscious that she would worry about me, and I didn't help matters by injuring myself frequently, including one accident involving a less-than-graceful descent down a flight of stairs and almost three weeks in hospital with a subarachnoid haemorrhage (that's a sore brain to you and me).

"Well nothing's changed to be honest," she explained. "I still get nervous in the dark because I forget that not everyone has your condition and have to restrain myself from helping them."

I'm sure she will get over it eventually, but I won't, and I'm conscious that, as I get older, I might need to depend on other people more and go out by myself less, and will increasingly relinquish some of the autonomy that has always been so important to me. I am not sure it is a burden I want to put on another person, not least a partner with whom I'd like to have an equal relationship. I've already given up on clubs for the most part, and even restaurants or the cinema can be problematic. I'm still figuring out how I will continue to earn a living, read books, do shopping and simply get by with the daily tasks that require no thought now, but which will become increasingly problematic - misplacing my keys can mean a delay of up to half an hour in
getting out of the house.

But while I am starting to make tentative changes to my lifestyle, my plans and my expectations, my brother hasn't even left the starting blocks. He refuses to acknowledge the problem, on the basis that, since no treatment exists, it doesn't bear thinking about. I can see where he is coming from, but I wonder when he will finally start to address our condition and the impact it will have on his life.

Most frustrating for me has been the reaction people have to me since I started using my white cane. While the condition makes more of the world invisible to me with each passing day, my white cane marks me out as more visible to everyone who sees it. I can just about cope with the staring, and explaining over and over why I need the cane to people confused by the fact that I can clearly focus on them. More difficult have been comments from passersby who assume I need assistance and will insist on giving it no matter how many times I tell them to take their hands off me.

The comments have ranged from the well-meaning but infuriatingly patronising to the mind-bogglingly bizarre. "Been playing golf have you?" was one of the many gems that came my way recently. I know I'm blind, but I didn't think they were actually playing golf with white sticks these days. I've been man-handled on more than one occasion, bundled into taxis by panicking drivers and yanked around by a train company employee like a piece of oversized luggage. I'm a relatively patient person, but I regularly find myself wanting to punch these people. Lucky for them I'm a dedicated pacifist.

This is probably the bit where I am meant to talk about the positive things; the kindness of strangers, other things in life being opened up to me as a result of my condition. But that would just be blah. RP is the frustrating and tiring reality of my life. And it is with sadness that I must acknowledge that, because of my failing eyes, I will never score the winning goal for Scotland in the World Cup final.

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