A teenager in the United Kingdom described as a “fussy eater” partially lost his vision due to a strict diet of Pringles, French fries, white bread, processed ham and sausage.

A case study published Monday in Annals of Internal Medicine, shows the boy suffered from nutritional optic neuropathy, a dysfunction of the optic nerve cause by a diet low in nutrients required for nerve fibres in the eye to function. The condition can lead to permanent vision loss if left untreated.

Researchers at the Bristol Eye Hospital in the U.K. said the boy first visited his family doctor as a 14-year-old with a normal body mass index, but complained of tiredness. His doctor gave him some vitamin B12 injections to treat low levels of the vitamin and suggested some dietary changes.

A year later, the boy had developed hearing loss and symptoms related to his vision, but doctors could not determine the cause. By age 17, the boy visited the Bristol Eye Hospital with serious vision loss.

“He presented with blurred vision and blurred mainly in the centre of his vision, in fact his peripheral vision is intact,” Dr. Denize Atan, an ophthalmologist at the Bristol Eye Hospital who treated the teenager, told CTV News Channel. “He also had reduced colour vision and there were other signs to show that he had a dysfunction of his optic nerves.”

Doctors investigated and found the boy suffered several bone, vitamin and mineral deficiencies. That was when the teenager admitted to avoiding foods with certain textures since elementary school. He said he only ate French fries, Pringles, white bread, processed ham and sausage.

By the time doctors had completed the diagnosis, he had suffered permanent vision loss.

“Nutritional optic neuropathy if it’s caught early is very treatable and the vision problems all get better with treatment,” Atan said. “The problem in this case is that actually, he had been following this restricted diet for a number of years and so by the time that we had seen him, he had already developed some permanent damage to his optic nerves.”

Atan said doctors gave the teenager supplements to correct some vitamin deficiencies, and his colour vision improved, though his overall vision did not.

“A good thing is that he didn’t get worse,” she said. “Had his nutritional deficiencies continued, he could well have caught even more serious problems.”

Though nutritional optic neuropathy is rare in developed countries, the University of Iowa documented a case in which a 28-year-old man’s diet consisted almost entirely of 1.9 litres of vodka per day, causing vision problems.

The authors of the U.K. case study say “fussy eating” restricted to junk food that causes serious nutritional deficiencies is a form of eating disorder.

The researchers say nutritional optic neuropathy should be considered in all cases of unexplained vision loss involving someone with a poor diet, regardless of the person’s BMI.

Atan said any parents with a picky-eating child should not worry about them developing vision loss as such a selective diet doesn’t tend to last.

“Picky eating is often a phase that children go through and they grow out of,” she said. “Parental anxiety about the picky eating can almost make things worse. It’s better to introduce one or two new foods in each meal, but not get too angry or confrontational if your child doesn’t accept those foods.”