Corneal topography in atypical pellucid marginal degeneration

Purpose. Pellucid marginal degeneration (PMD) is commonly described as a no ninflammatory corneal ectasia typically involving the inferior cornea. Alth ough reports of superior corneal changes in PMD exist, the topographic patt erns of these PMD variants are not well characterized. We describe corneal topographic alterations seen in eyes with atypical PMD. Methods. Computer-a ssisted videokeratography was performed in 10 eyes of five patients with PM D. Results. Eight of the eyes studied had changes involving the superior co rnea, with or without changes in the inferior cornea. Atypical presentation s of PMD included extension of inferior peripheral thinning above the horiz ontal meridian and occurrence of superior corneal thinning and ectasia with or without typical inferior changes. Atypical PMD reveals topographic patt erns similar to classic PMD, but corneal changes also involve the nasal, te mporal, or superior quadrants or a combination of these. The topographic ma ps reflect the location of peripheral corneal thinning and extent of cornea l protrusion. Conclusions. Corneal topographic changes in atypical PMD are similar to those seen in typical PMD but can involve the superior cornea.