The family of a teenager, from Bristol, who suffered irreversible eyesight loss after surviving on a diet of chips, white bread and processed snacks and meat have spoken of their heartache.

The teenager, now 19, has been a fussy eater from an early age and cannot tolerate the texture of fruit and vegetables.

His poor diet caused him to suffer from nutritional optic neuropathy, which is treatable if diagnosed early. In his case, fibres in his optic nerve have been so badly damaged that the harm to his sight has been judged to be permanent.

Speaking anonymously, the teenager’s mother said he could not find work and had had to abandon a college course in IT.

She said her son became a fussy eater when he was about seven and would only eat chips, crisps, sausages, processed ham and white bread.

“The first we knew about it was when he began coming home from primary school with his packed lunch untouched,” she said.

“I would make him nice sandwiches – and put an apple or other fruit in – and he wouldn’t eat any of it. His teachers became concerned, too.

“His brother and sister have never stopped eating. They love everything. He has always been skinny, so we had no weight concerns. You hear about junk food and obesity all the time – but he was as thin as a rake.”

The family only realised something was seriously wrong when his hearing began going at the age of 14 – and his vision soon after.

The woman said: “His sight went downhill very fast – to the point where he is now legally blind.

“He has no social life to speak of now. After leaving school he got into college to do a course in IT. But he had to give it up because he could not see or hear anything.

“He would love a job, but he has not been able to find anything he can do. I had to quit my job in a pub. I now look after him full-time. He is taking vitamin supplements, but his diet is still pretty much the same.

“When he was having counselling we managed to start him on fruit smoothies. But he’s gone off those now.”

The boy suffers from an eating disorder called Arfid (avoidant restrictive food intake disorder). Sufferers become sensitive to the taste, texture, smell and appearance of certain types of food.

His mother, in her 40s, said: “We couldn’t believe it when we were told what had happened. We are told the damage is irreversible. It’s been a nightmare.

“My son would love a job where he can sit at a desk and be useful. His siblings are doing well. It’s heartbreaking.”

The 19-year-old agreed for his case to be reported in the Annals of Internal Medicine to raise awareness.

At the age of 14, he was diagnosed with vitamin B12 deficiency and put on supplements, but he did not stick with the treatment or improve his poor diet.

Dr Denize Atan, who treated the teenager at Bristol Eye Hospital, said: “He had a daily portion of fries from the local fish and chip shop and snacked on Pringles, white bread, processed ham slices and sausage.

“He explained this as an aversion to certain textures of food that he really could not tolerate, and so chips and crisps were really the only types of food that he wanted and felt that he could eat.”

Atan and her colleagues re-checked the young man’s vitamin levels and found he was low in B12 as well as some other important vitamins and minerals. He was not over or underweight, but was severely malnourished.

The paper said it was well-known junk food increased the risk of poor cardiovascular health, obesity and cancer. But it warned not everyone realised that poor nutrition could also permanently damage the nervous system, particularly vision.