A teenage boy's diet reportedly caused him to go blind, and his story is bringing light to an uncommon and potentially-dangerous eating disorder.

According to a case study in the journal Annals of Internal Medicine, the teenager went to the doctor when he experienced trouble hearing and seeing. Doctors discovered that he was vitamin B12 deficient, which led them to do more tests, and eventually diagnose him with an eating disorder called avoidant-restrictive food intake disorder (ARFID).

The case report says ARFID is a relatively new disorder, which used to be called "selective eating disorder." The patient was diagnosed with ARFID after years of eating only certain unhealthy foods like potato chips and French fries.

Unlike other eating disorders, “[ARFID] is not driven by weight or shape concerns,” the case report says. In fact, people with the disorder often have a normal BMI, as was the case with the patient who lost his eyesight because of his diet.

“Height and weight were average, and body mass index was normal. However, the patient confessed that, since elementary school, he would not eat certain textures of food,” the case report says. “He had a daily portion of fries from the local fish and chip shop and snacked on Pringles (Kellogg), white bread, processed ham slices, and sausage.”

According to the case report, people with ARFID “lack interest” in food. Their sensitivity to certain food textures is heightened, and they are afraid of what will happen if they eat certain foods. According to the National Eating Disorders Association (NEDA), the disorder can cause weight loss, lack of appetite, and gastrointestinal problems, among other issues. The association adds that people with the disorder can be scared of vomiting and choking.

The disorder caused the patient to have a confirmed vitamin B12 deficiency, and the report says the patient likely also suffered from deficiencies in the following nutrients: B1, B2, B3, B6, B9, and copper.

The boy's vision loss, however, is the most jarring part of the case report, and while it might not be a primary concern when it comes to eating disorder, the four UK-based authors of the case study argue that doctors should be aware that one’s diet can drastically affect their eyesight.

“Popular media have highlighted the risks for poor cardiovascular health, obesity, and cancer associated with junk food, but poor nutrition can also permanently damage the nervous system, particularly vision,” the report says.

By the time doctors figured out what had happened to the patient featured in the report, it was too late. “He was prescribed nutritional supplements that corrected his deficiencies and was referred to mental health services for his eating disorder,” but this eyesight did not improve, according to the report.

Eventually, the boy was diagnosed with nutritional optic neuropathy, or a dysfunction of the optic nerve from nutritional deficiencies that left him blind. The case report notes that, aside from ARFID, nutritional optic neuropathy can be caused by drugs and a combination of poor diet and alcohol use or smoking. While the damage done to one’s eyes is reversible if it’s caught by a doctor early enough, the patient featured in the case report suffered from irreversible damage.

Overall, study authors said that, "nutritional optic neuropathy should be considered in any patient with unexplained vision symptoms and poor diet, regardless of BMI."