Patients with PMD mostly presented in their third to fourth decade of life with decreased visual acuity due to increase in against-the-rule astigmatism. This ectatic disease commonly involves the inferior cornea, with an area of thinning extending from the 4-o´ clock to the 8-o´ clock positions. The term “pellucid” means clear and first time was used by Schlaeppi to describe the corneal clarity and the absence of lipid deposition, scarring or vascularization, despite the presence of ectasia. Pellucid marginal degeneration (PMD) is an idiopathic, progressive, noninflammatory, ectatic corneal disease characterized by a peripheral crescent of inferior corneal thinning. Updates on management of pellucid marginal degeneration: Topographic patterns, differential diagnosis, and surgical options. Keywords: Differential diagnosis, pellucid marginal degeneration, surgical options, topographic patterns Different surgical techniques are available for PMD management however, none of them were found to be effective, so further studies will be needed in the future. Spectacles, soft and rigid gas permeable contact lens are the main visual correcting method in early stage of the disease. Corneal topography is the main diagnostic tool of PMD with characteristic diagnostic patterns “crab-claw” or “butterfly.” PMD could be mistaken as KCN, keratoglobus, and other peripheral thinning conditions such as Terrien marginal degeneration and Mooren's ulcer. It is difficult to differentiate between keratoconus (KCN) and PMD by slit lamp, especially in the detection of early and subclinical stages of the diseases. Pellucid marginal degeneration (PMD) is a rare ectatic corneal disease involving the inferior part of the cornea. All rights reserved.DOI: 10.4103/sjopthal.sjopthal_20_20 Abstract This review describes the clinical features of PMD, its differential diagnosis and various management strategies presently available.Ĭopyright © 2010 British Contact Lens Association. Since patients with PMD make poor candidates for laser vision correction, an awareness of the topographical and slit-lamp features of PMD will be useful to clinicians screening for signs of corneal abnormality before corneal refractive surgery. Several surgical procedures have been used in an attempt to improve visual acuity when spectacles and contact lenses do not provide adequate vision correction. The vast majority of PMD patients are managed using spectacles and contact lenses. In rare cases, patients may present with a sudden loss of vision and excruciating ocular pain due to corneal hydrops or spontaneous perforation. Visual signs and symptoms include longstanding reduced visual acuity or increasing against-the-rule irregular astigmatism leading to a slow reduction in visual acuity. Unless corneal topography is evaluated, early forms of PMD may often be undetected however, in the later stages PMD can often be misdiagnosed as keratoconus. Ocular signs and symptoms of patients with PMD differ depending on the severity of the condition. The prevalence and aetiology of this disorder remain unknown. The condition is most commonly found in males and usually appears between the 2nd and 5th decades of life affecting all ethnicities. Pellucid marginal corneal degeneration (PMD) is a rare ectatic disorder which typically affects the inferior peripheral cornea in a crescentic fashion.
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