Terrien's marginal degeneration: clinicopathologic case reports.

We report the clinicopathologic features of seven cases of Terrien's marginal degeneration. Three specimens studied were lamellar resections and four were full-thickness corneal segments. Of the four full-thickness specimens, three were semilunar and one was an annular ("doughnut-shaped") specimen. All cases had stromal thinning, vascularization, lipid keratopathy and local absence of Bowman's membrane. Descemet's membrane was markedly thickened and the endothelium was intact. Three of the four full-thickness corneal specimens showed healed ruptures of Descemet's membrane. One specimen had four healed successive ruptures in Descemet's membrane in the same area. The corneal endothelium in that area had produced a basement membrane that totalled 35 micron in thickness. The clinical and histopathologic features of pellucid and Terrien's marginal degeneration are similar. When idiopathic peripheral corneal thinning remains clear, it is regarded as pellucid degeneration; vascularization, scarring, and lipid keratopathy are regarded as Terrien's marginal degeneration. Breaks in Descemet's membrane contribute to these latter changes.