Pellucid Marginal Degeneration (PMD) Differential Diagnoses

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

Diagnostic Considerations

Keratoconus 

Keratoconus is the major mimicker of pellucid marginal degeneration.

Similarities between PMD and keratoconus have been attributed to the absence of firm criteria for each disease entity.

Keratoglobus 

Keratoglobus causes generalized thinning of the cornea.

The thinning is most marked at the limbus, extending circumferentially for 360°.

The whole cornea protrudes, in contrast to the regional thinning seen in keratoconus and the inferior paralimbal thinning in pellucid marginal degeneration.

Terrien marginal degeneration

Terrien marginal degeneration affects an age group similar to that affected by pellucid marginal degeneration.

Terrien marginal degeneration can be bilateral.

Although this condition can be associated with large amounts of astigmatism, it can be differentiated from pellucid marginal degeneration because the superior cornea is predominantly affected and because the area of thinning is often associated with vascularization and lipid deposition.

Furrow degeneration

Furrow degeneration has some features of pellucid marginal degeneration.

An intact epithelium is present, and the area of corneal thinning is not vascularized, at least in the acute phase.

The differentiating feature is that the area of thinning is closer to the limbus with virtually no intervening zone of normal cornea, unlike the findings in pellucid marginal degeneration.

Furrow degeneration occasionally involves the superior cornea, and an associated adjacent area of scleritis may be present.

Edges of the furrow are steeper than the gradual attenuation seen in pellucid marginal degeneration.

Furrow degeneration occurs adjacent to the lipid deposition in arcus senilis, which is typically observed in elderly patients.

Peripheral corneal melting disorders

Peripheral corneal melting disorders, such as Mooren ulcer, or peripheral melting secondary to rheumatologic disorders are characterized by pain.

This pain may be severe in cases of Mooren ulcer.

Associated findings include an epithelial defect over the area of thinning and corneal vascularization adjacent to the area of thinning in the acute phase.

Contact lens–induced warping of the cornea

Contact lens–induced warping of the cornea can mimic the appearance of pellucid marginal degeneration on corneal topography.

Differential Diagnoses

  • Contact Lens Complications

  • Furrow degeneration

  • Keratoconus

  • Keratoglobus

  • Mooren ulcer

  • Terrien marginal degeneration