A severe case of avoidant-restrictive food intake disorder led to blindness in a 17-year-old boy, who for approximately seven years ate only French fries, chips, white bread, and processed pork, according to a case report published Monday in the Annals of Internal Medicine.

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The boy's diet—and his health

Denize Atan, who is the clinical lead for neuro-ophthalmology at Bristol Eye Hospital in England and the lead author on the case report, first saw the boy, a United Kingdom resident, when he was 14-years-old, and he had reported chronic "tiredness." According to the case report, the patient was known to be a picky eater, but was "otherwise well … took no medications," and was not overweight.

At age 15, the patient's hearing and vision began to deteriorate, but doctors could not determine the cause. Two years later, the patient's vision had deteriorated so much that he was deemed legally blind.

The patient again saw Atan, and testing revealed that he still had low levels of vitamin B12. In addition, the patient had developed low levels of copper, selenium, and vitamin D, and high levels of zinc. The patient also had "lost minerals from his bone, which was really quite shocking for a boy of his age," Atan said.

But Atan said the most surprising finding was how long the patient's poor eating habits had persisted. According to Atan, the boy said he'd maintained the same diet—consisting of "a daily portion of fries from the local fish and chip shop," as well as "Pringles [chips], white bread, processed ham slices, and sausage," without any fruits or vegetables—for about seven years.

According to Atan, the patient's "aversion to certain textures of food" meant "that he really could not tolerate" a large variety of foods, and "chips and crisps were really the only types of food that he wanted and felt that he could eat."

A diagnosis

Providers ultimately concluded that the boy's diet—which was lacking in variety, healthy foods, vitamins, and minerals—caused the patient's blindness.

They diagnosed the patient with nutritional optic neuropathy, which is a dysfunction in the optic nerve. The condition often is reversible if caught early but, when left untreated, the condition can lead to permanent optic nerve damage and blindness. In the boy's case, the condition has caused "blind spots right in the middle of his vision," according to Atan.

Providers also diagnosed the boy with avoidant-restrictive food intake disorder, which is a condition in which a person has a strong aversion to certain food textures or fears the consequences of eating certain foods, the Washington Post reports.

The importance of a balanced diet

The boy's case "highlights the impact of diet on visual and physical health, and the fact that calorie intake and [body mass index] are not reliable indicators of nutritional status," according to Atan.

The case also reinforces that "poor nutrition can … permanently damage the nervous system, particularly vision," the researchers wrote.

However, Atan conceded that the patient's case is very rare. "Nutritional deficiencies are actually quite common, but nutritional blindness is not," she said. However, she added, "Blindness is an uncommon but serious complication of poor nutrition."

The researchers also raised concerns that nutritional optic neuropathy may become more common due to an increase in consumers' consumption of junk food, as well as the increasing popularity of veganism, which can result in B12 deficiencies.

"It is important to eat a varied diet," Atan said. "There is not a single food that will provide all the vitamins and minerals you need—variety is the key."

Allen Taylor, director of the Nutrition and Vision Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University who was not involved with the case report, also acknowledged the importance of a varied diet, but questioned whether poor diet was the sole cause of the boy's blindness.

"There is, absolutely, a link between poor diet and vision loss," Taylor said, but he noted that such symptoms typically don't present until later in life.

"It's intriguing," he said of the case report, "But it's important to remember it's a study of only one case with very limited information in it" (Paul, Washington Post, 9/3; Aubrey, "The Salt," NPR, 9/3; Reals, CBS News, 9/3).