The corneal topography is a key fadiagnosis Typically a bilateral condition, but iit can be rarely unilateral. Conclusion Pellucid marginal corneal degeneration is a rare idiopathic non-inflammatory ectatic corneal disease characterized by a narrow band of corneal. In advanced stages, more invasive treatments are necessary, such as corneal resections and transplants. The treatment is based, in early stages, on glasses, lenses or intracorneal rings. Topography confirms the diagnosis, as well as distinguishes MPD from other non-inflammatory ectatic diseases of the horn such as keratoconus, posterior keratoconus by classically showing a very peripheral inferior ectasia with a 'butterfly wing' appearance. Discussion The diagnosis of the disease is initially clinical, where functional signs include decreased visual acuity or worsening of significant irregular astigmatism, and biomicroscopy shows a thinned inferior corneal band. As a treatment, scleral lens placement in the right eye was proposed. In contrast, the left eye had a normal topographic appearance. Anterior astigmatism of-8.5 D at 107° was noted on the OD, and-0.4 D at 142.5° on the OG. On the axial map, we noted flattening of the upper vertical hemimeridians and camber of the oblique and lower vertical hemimeridians. Topography of the right eye showed corneal thinning that predominated inferiorly on the pachymetric map.The elevation maps objectified a corneal protrusion above the thinning area. The cornea of the adelphic eye is normal. In biomicroscopy, we observed a band of cornea thinned inferiorly, separated from the limbus by a crescent of normal cornea in the right eye. Results The clinical examination found a Best corrected visual acuity of 4/20 in the right eye (OD) and 20/20 in the left eye (OS). Methods We report the case of a 37-year-old female patient, without any particular history, who presented a progressive decrease in visual acuity of the right eye without any notion of redness or associated pain. The aim of our work is to study the clinical and topographic characteristics of the disease, its differential diagnosis and therapeutic strategies through a unilateral case and a review of the literature.

It is often confused with keratoconus because of clinical, histological and topographical similarities. Resume Introduction Pellucid marginal corneal degeneration (PMCD) is a progressive, non-inflammatory disease of the lower cornea.

Pellucid corneal degeneration