A TAVISTOCK father and son have started the countdown to a gruelling physical challenge, as they prepare to take on one of the highest mountains in the world while coping with a major disability.

Jacob Gibbins, 19, and his dad, Tim, 60, will leave for their attempt on Mt Kilimanjaro on February 17. The trek would be hard enough for anyone, but for Tim it will be a huge task, as he has now lost 80% of his vision to the condition Retinitis Pigmentosa.

Jacob, a freelance photographer, and Tim have been training hard for the eight-day trek, with regular gym sessions and long walks on Dartmoor, weighed down with full backpacks.

Jacob said: 'The trek will be really hard from start to finish. The fact my dad's blind will make it harder still — our biggest worry is the altitude as there's nothing you can do to train for it, and altitude sickness can get anyone — young, old, fit or fat.'

The pair have been getting all their gear sorted during the last few weeks — the weather on the mountain can be icy cold.

'We have been told it can get to -20 to -30 degrees on the summit so lots of gloves, and special jackets have been bought,' said Jacob.

'For me, the hardest part has just been the mental preperation. Getting ready for over a week's walking at high altitude will be very draining on both body and mind. My dad has been in the gym a few times a week and has also given up smoking so for him I think the altitude will be the hardest part.'

It will take six days for Jacob and Tim to make the ascent of the mountain, and two down. They plan to walk between 20 and 30 kilometres uphill every day, through rough terrain at heights well over 15,000ft.

The pair have now managed to raise £2,000 for the British Retinitis Pigmentosa Society — and have also completed the challenge of organising flights, coaches, insurance, visas, and vaccinations.

Anyone who would like to support Jacob and Tim by raising money for such an important cause should go to http://www.justgiving.com/blindsummit2011">http://www.justgiving.com/blindsummit2011