A teenager who lived on Pringles, chips and processed ham went blind due to the lack of vitamins in his diet.
The boy from Bristol, who is now 19, has not eaten any fruit or vegetables for almost a decade despite pleas from his desperate parents.
He eats just one meal a day – a portion of chips – and supplements this with Pringles and the occasional deep-fried sausage, slice of white bread or processed ham.
The unnamed teenager began to go blind when he was 15 and had a flurry of diagnostic tests over two years before doctors finally realised his deteriorating eyesight was caused by his diet.
A review of his case, published in the Annals of Internal Medicine journal, found that he was deficient in several key vitamins, including vitamin B12, copper and vitamin D.
The boy was not overweight and was of average height, but the vitamin deficiencies caused irreversible damage to his optic nerve and he is now partially sighted.
Dr Denize Atan, who treated the teenager at Bristol Eye Hospital, said: "This is the most serious case I’ve ever seen of blindness caused by junk food. Since he was 11 he had developed extreme picky eating. His main staples were chips and crisps, then every now and then he would buy a sausage from the fish and chip shop, or have a slice of ham. He only had one meal a day and would just snack on Pringles. He was getting enough calories but not enough nutrition.
"His parents had tried everything they could... but he would not eat anything else so they felt they had no choice but to buy him chips. His siblings eat a normal diet."
The boy first went to his GP aged 14, complaining of tiredness, and was diagnosed with vitamin B12 deficiency.
At 15, he began to experience hearing loss and vision problems and his eyesight deteriorated over the next two years. Dr Atan added: "He had seen a number of other doctors but they hadn’t quite twigged the link between the diet and his poor vision. Unfortunately it was picked up too late for him to have a chance of recovering his lost vision."
Vitamin B, found in whole grains, eggs and leafy vegetables, is vital to maintaining good eyesight. Deficiency in B12 can damage the optic nerve, disrupting the signal that travels from the eye to the brain.
The doctors who treated the teenager have published details of his case to make other health professionals aware that poor diet can lead to blindness.
The 19-year-old has not changed his diet, but is receiving treatment for an eating disorder. He is taking vitamin supplements and his colour vision has improved slightly. The report said: ‘The patient confessed that, since elementary school, he would not eat certain textures of food.
"He had a daily portion of fries from the local fish and chip shop and snacked on Pringles, white bread, processed ham slices and sausages."
The authors said nutrient deficiencies were becoming more common due to the popularity of junk food and Britain’s child obesity epidemic. NHS figures show that one in five children is obese at the age of 11.