University of Iowa Health Care

Ophthalmology and Visual Sciences

EyeRounds.org

Pellucid marginal degeneration

Category: Cornea & External

Contributor: Jesse Vislisel, MD

Photographer: Carol Chan, CRA

Pellucid marginal degeneration is a bilateral corneal ectasia that results in inferior corneal thinning with a corneal protrusion above the thinnest area. This is in contrast to keratoconus where maximal thinning occurs at the apex of the protrusion.

Figure 1: These slitlamp photographs demonstrate the corneal protrusion above the area of inferior thinning in a patient with pellucid marginal degeneration.
slit lamp image, right eye slit lamp image, left eye

 

Figure 2: The Pentacam Scheimpflug cross-sectional images from the patient in Figure 1 show the contour changes associated with the inferior stromal thinning.
Pentacam cros-sectional image, left eye Pentacam cros-sectional image, right eye
Figure 3: The axial curvature and anterior float Pentacam topography maps from the patient in Figure 1 reveal the characteristic high against-the-rule astigmatism pattern seen in patients with pellucid marginal degeneration. Inferior steepening is also present, as seen grossly in the images in Figures 1 and 2, but is too peripheral in the case to be captured on the topography scans, thus the absence of the classic "crab claw" topographic appearance.
topography, left eye topography, right eye

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last updated: 03/15/2016
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