Pellucid marginal corneal degeneration in a teenager.

A teenage boy presented to the clinic complaining of poor vision in both eyes. His best-corrected visual acuity was 20/25. The slit lamp examination revealed vertically oval corneas, crescentic peripheral inferior corneal thinning and ectasia in both eyes. Corneal topography showed against-the-rule astigmatism with mean keratometry (Km) of 45.1 and 45.2 dioptres in the right and left eyes, respectively. High-resolution optical coherence tomography corroborated the clinical findings, and the patient was diagnosed with pellucid marginal corneal degeneration (PMD). Collagen cross-linking was performed in the right eye. Left eye cross-linking is awaited. Although PMD is typically seen in middle-aged (third-fourth decade) patients, it can also occur at earlier ages. Collagen cross-linking can be considered to prevent the progression of the condition.