Pellucid Marginal Degeneration Workup
- Author: Karim Rasheed, MD, MSc; Chief Editor: Hampton Roy, Sr, MD more...
Optical coherence tomography (OCT) and Scheimpflug-based corneal imaging systems can illustrate inferior corneal thinning (see image below).
Computerized videokeratography is extremely useful in detecting and diagnosing early disease, which may not be readily detectable on slit lamp evaluation. Videokeratography shows low corneal power along the central vertical axis, increased power as the inferior cornea is approached, and high corneal power along the inferior oblique meridians. The videokeratographic pattern has a classic butterfly appearance, as shown in the image below.
Pachymetry may reveal a thinning of the inferior cornea. This is a reversal of the typical pattern in which the cornea thickens from the center to the periphery. If any part of the peripheral cornea is thinner than the center, this is a cause for concern.
Orbscan may reveal a typical "kissing birds" appearance.
Histologic examination shows an area of thinning that is epithelialized, clear, and avascular. The stroma is thinned, and the Bowman layer may have breaks or may be completely absent in the affected area. Typically, lipid deposits are absent, and a normal-appearing endothelium and the Descemet membrane are present. In acute hydrops, breaks in the Descemet membrane with swelling of the stroma and inflammatory cell infiltrate may be seen.
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