I loved to read. From childhood, the printed word allowed my imagination to soar across the centuries. Now I no longer buy books or visit libraries. One evening in late September 1998, as I read, the final letters of each sentence pirouetted in a crooked dance.

During the next few days, horizontal and vertical lines appeared distorted. Bookshelves sagged, Regency buildings in Cheltenham lost their straight edges and staggered in Gothic frenzy. Roofs were askew and signs lurched. People’s faces and bodies changed, too. Their limbs and torsos grew long and thin. Tiny heads with unrecognisable, grimacing features perched on elongated necks; the human race glimpsed grotesquely in a funfair mirror. Only the humour escaped me. I felt dizzy and frightened in this shifting and disintegrating world.

I’d always had poor vision in my right eye, but something extraordinary was happening to the left eye on which I depended. The changes occurred over a month without warning. Was this a psychosomatic condition, perhaps stress-related, or was I going blind?

An ophthalmic consultant diagnosed macular degeneration. He told me my central focus could deteriorate further but that peripheral vision would be retained. The spectre of total blindness receded. My focus did become fuzzier, but distorted lines and shapes gradually righted themselves, although objects or faces disappeared if I looked at them directly.

I had never heard of macular degeneration - but I’ve since discovered it is the most common cause of visual impairment in the over-sixties. It is brought on by blood vessels leaking into and damaging the macula, the focal point at the back of the retina. The condition is most likely to occur in extremely short-sighted people like me. No preventive measures are available.

Initially I could read and mark using strong magnifying lamps, and I taught “headless” students. But by March, even the lamps were useless and I was finding work increasingly frustrating. I could read only by holding the print an inch from one eye, a few words at a time. Small print defeated me. Marking became impossible and trying to do A-level revision with texts for the historiography paper proved a nightmare.

The support and goodwill of my colleagues at the Cheltenham Ladies’ College - an independent girls’ boarding school in Gloucestershire - kept me afloat. One was appointed as my official amanuensis, her eyes guiding me through the mounds of paperwork that haunt every head of department. For a reluctant computer-user now unable to see the keys or read the screen, there was no salvation in technology.

I became exhausted and found sustaining a full teaching day difficult. My eyes ached from trying to see, and I had frequent headaches. For as long as I could decipher their work, the students wrote or typed in large black letters. One said: “Even if she can’t read or write, she can talk and that’s fine.” The comment reminded me of Maureen Lipman’s line in an old BT advertisement: “These teachers can’t mark - some of them can’t even see.”

It was inconceivable to start another academic year relying on the generosity of hard-pressed colleagues. Constantly having to ask for help is debilitating. Then, through a chance encounter with a fellow dog-walker, I discovered the Disability Discrimination Act. I contacted the local disability employment adviser and found that under the Access to Work scheme I could be assessed at a Royal National Institute for the Blind centre, and trained in skills that might enable me to work effectively again, albeit in another career.

Thus, during a glorious week in June 1999, I attended Manor House College in Torquay. After struggling - sometimes tearfully - in the sighted world for eight months, I found myself in an environment where being unable to see was normal. It was like coming home. I completed language, number and spatial tests reminiscent of the 11-plus. I tried out a TV device that enlarges print and pictures on to a screen. The opportunity to discuss my sight loss with staff, some of whom were visually impaired, and to have time for reflection was invaluable.

Conversations with the occupational therapist opened up interesting possibilities. Should I become a writer and breed from my Cairn bitch, puppies playing around my feet as I write great novels? Or retrain to do a therapist’s job or teach on a one-to-one basis? One thing was definite - I needed touch-typing and computing skills. I left the interview joyfully optimistic, convinced that choices existed.

I’d gone to Manor House believing I ought to return to teaching at Cheltenham. But even with technological help and 40 per cent more effort, I would work more slowly than before the sight loss. At 58, did I want to make this effort? The contemplation of a different life excited me, whereas envisaging the refurbished old one depressed me.

One Manor House tutor noticed that when I spoke of teaching, my body language grew hostile, even though I spoke positive words. Taking a term’s sick leave to follow an Access to Work course enabled me to make an informed decision.

I spent the summer coming to terms with visual impairment. I had to get used to carrying a white cane. It felt awkward despite its necessity - especially for crossing roads, as I find evaluating the speed and distance of cars difficult, while bicycles can disappear altogether.

A friend was reading Harry Potter to me, and I partially conquered the reluctance to use the cane by mentally transforming it into a wand. Not seeing, I sometimes feel like Harry Potter wrapped in his invisibility cloak, and forget that I can be seen. I am surprised that passers-by ask me the way. Even car drivers screech to a halt requesting directions to Oxford or Stroud.

Gadgets for the blind entrance me - talking clocks and a watch that crows like a cockerel are very pleasing. I now have an extra pet: an electronic parrot which, at the press of a button, repeats recorded phone numbers, addresses and other useful information. I’ve resisted the talking microwave. But the best discovery is the talking book service. The spoken word has replaced the written, the slower pace of listening increasing my sensitivity to nuances of language.

Although tempted to return to Torquay, I opted for Queen Alexandra College in Birmingham, because it was close to home. On September 20, I arrived at Birmingham New Street station. Bewildered by the plethora of signs, timidly waving the cane, I asked for the exit. The answer came: “You’re standing under the exit sign. Use your eyes.”

Queen Alexandra is a charity that caters for students from 16 to retirement age and beyond. It aims to give people with visual impairment and other disabilities the skills they need to live and work independently. Each student learns Braille or Moon and is given an individual programme and a personal tutor. As well as the six to nine-week access courses that equip those with recent sight loss to continue in work or to undertake further vocational training, it offers training in job-seeking, and application and interview techniques. The college also organises work experience placements.

I lived on campus and worked in the IT department, learning to touch-type and master basic computer commands. I could read the screen with an enlargement program. When tired, I relied on the voice, Hal, which read everything on the screen to me. I soon developed a rapport with this Dalek-like assistant.

I looked forward to a weekly visit to the art block, where I experimented with clay. Some of the clay sculptures there were the work of a student blind from birth.

Mobility lessons increased my confidence in using my cane. I’ve never had a good sense of orientation and soon realised that survival demanded concentration. I developed an acute awareness of landmarks in the street and buses, which allowed me to travel more independently - even from New Street.

I was now a student, but old habits die hard and it felt strange not to be allowed into the staffroom. Receiving progress reports was a novel experience, too.

I enjoyed the humour and companionship of the IT students and staff. The two guide dogs, Imogen and Lance, waited patiently during classes, occasionally emitting heavy sighs. I longed for my terrier to become my guide dog, but she’s the wrong shape and temperament.

I felt sad to leave after nine weeks. I could now touch-type, and computers no longer spooked me - although a recalcitrant machine can still reduce me to gibbering rage.

While at Queen Alexandra College I realised I could no longer teach. I had to move on. I applied for early retirement and here I am, a year on, beginning as a freelance writer. The loss of focus distressed me and radically changed many assumptions. But I have discovered an alternative focus and a fulfilling life.

Genevieve Matley was head of history at the Cheltenham Ladies’ College from 1991-1999Queen Alexandra College, tel: 0121 428 5050. Website www.qac.ac.uk