A teenager has gone blind and left partially deaf after living on a diet of chips and sausages for several years.
The boy first presented to his doctor aged 14, complaining of tiredness, but his condition deteriorated and by the age of 17 he had "permanently impaired vision."
Since primary school, he had relied on a diet of chips, Pringles, white bread, processed ham slices and sausages.
His diet was so poor he developed a condition, usually only seen in malnourished children in developing countries.
By the time his condition was diagnosed, the patient had permanently impaired vision
The teenager's lack of nutrition had severely damaged his optic nerve, causing a condition known as nutritional optic neuropathy (NON).
The Bristol boy took no medication and had a normal body mass index (BMI), but tests showed he had low vitamin B12 levels and macrocytic anaemia - a condition in which your body has overly large red blood cells.
He was given B12 injections and dietary advice, but when he returned a year later he had developed some hearing loss and impaired vision, though still no cause was found.
According to the NHS, good sources of vitamin B12 include meat, salmon, cod, milk, cheese, eggs and some fortified breakfast cereals.
The case was published in the Annals of Internal Medicine.
"By age 17, the patient's vision had become progressively worse, to the point of blindness," the report said.
Investigating the boy’s nutrition, physicians found vitamin B12 and vitamin D deficiencies, a reduced bone mineral density, low levels of copper and selenium, and a high zinc level.
“The patient confessed that since elementary school, he had avoided foods with certain textures and only ate French fries, Pringles, white bread, processed ham slices, and sausage,” the report said.
It cautioned that nutrition-related optic damage should always be considered by doctors finding any patient with unexplained vision symptoms.
Study lead author Denize Atan, an ophthalmologist at Bristol Medical School and Bristol Eye Hospital, told ITV News it is very uncommon to go blind from a nutritional deficiency.
"The problem with this case, is that his particular eating behaviour had gone on for several years, had become entrenched and had led to multiple deficiencies," Dr Atan said.
"By the time he saw me, there was evidence he had damage to his optic nerve, that meant his potential for recovery, even with treatment, is more limited."
She said medical professionals will be left surprised patients could become blind from purely dietary means.
"That was one reason for publishing the case, to raise awareness about this, that it's important and it's a serious complication of nutritional deficiency," she said.
"I think sometimes we can be blase, about it and maybe think we can take vitamin supplements and that will protect us against any problems, but that's not true.
"It's much better to have a healthy, balanced varied diet to obtain all the vitamins and nutrients you need, rather than rely on supplements."
“The risks for poor cardiovascular health, obesity and cancer associated with junk food consumption are well known, but poor nutrition can also permanently damage the nervous system, particularly vision,” the report said.
“It is rare in developed countries. The condition is potentially reversible if caught early. But if left untreated, it leads to permanent blindness.”