Moonwalker - Adventures of a Midnight Mountaineer

IT was one of those classic yet all too rare winter days, the high mountains smothered in brilliant virgin white under a flawless blue sky and a ceaseless, radiant sun.

Yet the fierce wind whipping in from the east as we climbed to the summit of Ben More was a constant reminder of the time of year, the chill hitting -10, fingers frozen despite double layers, eyes stinging and watering from the bitter sideswipes.

We got some respite on the descent to the col and were never in a similarly exposed firing line on the continuing ascent to Stob Binnein. But the big surprise was still to come.

We dropped out of the snowline and down slopes of mud and grass, stopping to remove crampons which had now become a liability and packing away the axes. Ahead, the lowering sun was still managing to breach chinks along the Cruach Ardrain wall of summits with intense flashes of brilliance, a constant assault on the senses. And as we turned north into Benmore Glen for the final walk out, I suddenly lost my sight.

There was no warning: one moment I had perfect vision, the next I was plunged into near darkness. All I could make out were blurred contours and black shapes of distant ridge lines, jerky, shimmering movements on the horizon. It was though a dark veil had been drawn over the landscape. To say I was alarmed would be an understatement. I have had a few intimidating and unsettling experiences on the mountains, but this was easily the scariest.

I didn't mention anything to my companions, reckoning this was a temporary problem that would clear in the half hour we would take to reach the cars. I semi-stumbled along, concentrating on my foot placement where things seemed clearer, unable, or unwilling, to look up for fear of what I would or wouldn't see. It did start to ease, but there was no instant clarity. I still had to wait for a further hour or so in the car before I felt my sight had recovered enough for the drive home.

There were no after effects, and there has been no recurrence of the problem. It seemed I had been struck by a relatively mild bout of photokeratitis, more commonly known as snow blindness, which is triggered by overexposure to ultraviolet light. Basically, an excess of UV light from the reflections on the snow had given my corneas a sunburn. Severe cold and dryness may also have played a part, a more common problem at higher elevations.

My blurred and temporary loss of vision were typical symptoms. Sometimes you can also suffer from headaches or eye pain or the feeling that something is stuck in your eye. Four hours in blanket snow cover with a blazing sun, with the added complications of a freezing wind and spindrift strafing my face, had left me in a weakened position for the immediate stark contrast in the light when coming out of the white.

It was entirely self-inflicted. With the need to constantly be on the alert in full-on winter mountain conditions, I had neglected to put on my goggles at any point. It's not a mistake I shall make again.

Although current temperatures may suggest otherwise, winter is just around the corner. Shorter daylight hours and the prospect of sudden dramatic changes in the weather mean it's far easier to get caught out in the mountains.

This is the time to strip out your rucksack and do a major gear check: make sure everything is in a working state and you know how to use it. For instance, it's better to practise fitting your crampons at home than trying to remember how to do it when you're being buffeted on an icy mountain slope while wearing big gloves.

Change the batteries in your head torch, and remember to carry spares. I take two head torches on every hill walk. This started as a precaution because I was doing so many solo night walks, but it's especially important during the winter months. 

Only once have I had a torch die, and that was due to water ingress as I made my way off Cairn Gorm on a dark night with a blizzard raging around me. Having a spare to hand saved a lot of possible grief and anxiety. 

Also packed for every winter walk along with the required ironmongery and basic safety gear are three pairs of gloves, two hats – gloves and hats are in particular danger of being blown away – two spare pairs of socks, extra fleece and jacket, river waders, a two-person emergency shelter and a space blanket.

And definitely not to be forgotten from now on … goggles, or at the very least, sunglasses.