Pellucid marginal degeneration is a rare eye condition that affects the cornea, the transparent front layer of the eye. In this disorder, the cornea becomes thinner along its lower edge and bulges outward, altering its normal shape.

This irregularity leads to distorted and blurred vision that can significantly affect visual quality. Although it shares similarities with keratoconus, its thinning pattern is different, and it usually progresses slowly over time.