Scientists from the University of Bristol examined the case of a young patient whose extremely picky eating led to blindness, and have warned of the dangers of a poor diet.

The unidentified patient told doctors he had only eaten fries from the fish and chip shop, Pringles potato chips, white bread, slices of processed ham and sausage since elementary school, and he avoided foods with certain textures. He first visited a doctor at age 14, complaining of tiredness, according to a case report published in the Annals of Internal Medicine on Monday.

He wasn’t taking any medication, had a normal BMI and height, and showed no visible signs of malnutrition.