Pellucid Marginal Degeneration (PMD)

Updated: Oct 30, 2017
  • Author: Jean Deschênes, MD, FRCSC; Chief Editor: Hampton Roy, Sr, MD  more...
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Overview

Background

Pellucid marginal degeneration (PMD) is a bilateral, noninflammatory, peripheral corneal thinning disorder characterized by a peripheral band of thinning of the inferior cornea. The cornea in and adjacent to the thinned area is ectatic. Schalaeppi first coined the term pellucid marginal degeneration in 1957.

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Pathophysiology

The etiology of pellucid marginal degeneration has not been clearly established, but collagen abnormalities, as seen in keratoconus, have been reported. The thinned and presumably weakened cornea may protrude as a result of the positive intraocular pressure.

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Epidemiology

Frequency

United States

Pellucid marginal degeneration is rare, and the exact incidence and prevalence are unknown. However, the incidence may be considerably underestimated, as this condition is often misdiagnosed as keratoconus.

Mortality/Morbidity

Deterioration of visual function results from the irregular astigmatism induced by asymmetric distortion of the cornea. The deterioration in visual function is commonly severe.

Refractive surgery, such as photorefractive keratectomy (PRK), can cause severe corneal haze, and results with laser-assisted in situ keratomileusis (LASIK) are unpredictable.

Race

No racial preponderance has been identified for pellucid marginal degeneration.

Sex

There are controversies concerning the sexual predilection of pellucid marginal degeneration. Some studies have reported no difference, [1, 2] while others have reported a male predilection. [3, 4, 5] In a 2016 Japanese study of 162 eyes with pellucid marginal degeneration, 75% of the patients were men. [6]

Age

Patients are usually aged 20-40 years at the time of clinical presentation.

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Prognosis

The affected cornea maintains its clarity. However, patients experience progressive deterioration of vision due to irregular astigmatism. [6] The prognosis of pellucid marginal degeneration is clinical.

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