![]() ![]() 4 This results in a relatively steep contour approximately 90° away. Stromal thinning is known to cause corneal flattening over the area of tissue loss, and steepening at the border of unaffected tissue. Topographic analysis in our case revealed a characteristic bow-tie appearance of marked against-the-rule astigmatism oblique-inferiorly, without peripheral steepening. This rare entity has been postulated to be an abnormality of the connective tissue, 2, 3 but the exact pathogenesis is still unknown. Pellucid marginal degeneration is a bilateral, slowly progressive condition classically described between the second and fourth decades. The left eye was normal, with no evidence of corneal thinning, striae, or abnormal protrusion ( Figure 1, bottom). The intraocular pressure by applanation tonometry was normal in both eyes. The rest of the anterior and posterior segment was normal. There was no evidence of iron lines, lipid deposition, or vascularisation. The portion between the thinned area and limbus was normal in thickness. ![]() On slit-lamp biomicroscopy, the cornea in the right eye showed an irregular contour with a thin band inferiorly, approximately 1.5 mm in width and 2 mm from the limbus, with bulging above the thinned zone ( Figure 1, top). Ophthalmic examination revealed best-corrected visual acuities of 6/18 OD with −1.0/−13.50 D×110° and 6/6 OS unaided. There was no history of redness, pain, or use of ophthalmic medication during this time. Case reportĪ 46-year-old healthy Indian man presented with painless progressive diminution of vision in the right eye for 6 years. Described here is such a case, in which the other eye was normal. Unilateral isolated PMD is extremely unusual, and corneal topography provides valuable clues in suspected cases. 1 It is differentiated from other peripheral corneal thinning disorders such as Terrien's marginal degeneration and Mooren's ulcer by the absence of vascularisation, lipid infiltration, or corneal ulceration. Pellucid marginal degeneration (PMD) is a rare bilateral corneal disorder characterised by thinning in the peripheral portion of the inferior cornea with marked steepening just superior to the thinned zone. ![]()
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