Pellucid Marginal Degeneration

Updated: Sep 08, 2014
  • Author: Karim Rasheed, MD, MSc; Chief Editor: Hampton Roy, Sr, MD  more...
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Overview

Background

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

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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) may be unpredictable.

Race

No racial preponderance has been identified.

Sex

An equal distribution exists between the sexes.

Age

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

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