A BITOT'S SPOT is a sharply defined, gray or white lesion involving the exposed portion of the bulbar conjunctiva. Frequently bilateral, it is triangular in shape with its base at the temporal limbus and its apex extending toward the lateral canthus. The elevated, dry, lusterless surface of the Bitot's spot is distinctively frothy or foamy in appearance. The lesion is due to a keratinization of the conjunctival epithelium and is considered to be one of the classical features of vitamin A deficiency. As such, the Bitot's spot may be accompanied by night blindness or be followed by extensive xerosis of the conjunctiva, xerosis of the cornea, and keratomalacia.
However, there is an abundance of evidence to show that a deficiency of vitamin A is not the only cause for a Bitot's spot. For example, Bitot's spots have been seen in patients with pellagra, a vitamin B deficiency state. In addition,
Levine RA, Rabb MF. Bitot's Spot Overlying a Pinguecula. Arch Ophthalmol. 1971;86(5):525-528. doi:10.1001/archopht.1971.01000010527007