Bietti crystalline dystrophy: A genetic eye disease that leads to progressive night blindness and visual field constriction and is characterized by the formation of crystals in the cornea (the clear covering of the eye), yellow shiny deposits on the retina, and progressive atrophy of the retina and choroid (the back layers of the eye). Average age of onset is 29. Lipid inclusions are present not only in the cornea but also in blood lymphocytes, suggesting a systemic disorder of lipid metabolism. There is no known treatment. The disease is an autosomal recessive trait (the gene is on chromosome 4q35-qter) and is named for G. B. Bietti, an Italian ophthalmologist, who described it in 1937. Also called Bietti crystalline corneoretinal dystrophy.