Corneal Topography in Atypical Pellucid Marginal Degeneration

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PurposePellucid marginal degeneration (PMD) is commonly described as a noninflammatory corneal ectasia typically involving the inferior cornea. Although reports of superior corneal changes in PMD exist, the topographic patterns of these PMD variants are not well characterized. We describe corneal topographic alterations seen in eyes with atypical PMD.MethodsComputer-assisted videokeratography was performed in 10 eyes of five patients with PMD.ResultsEight of the eyes studied had changes involving the superior cornea, with or without changes in the inferior cornea. Atypical presentations of PMD included extension of inferior peripheral thinning above the horizontal meridian and occurrence of superior corneal thinning and ectasia with or without typical inferior changes. Atypical PMD reveals topographic patterns similar to classic PMD, but corneal changes also involve the nasal, temporal, or superior quadrants or a combination of these. The topographic maps reflect the location of peripheral corneal thinning and extent of corneal protrusion.ConclusionsCorneal topographic changes in atypical PMD are similar to those seen in typical PMD but can involve the superior cornea.

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