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MS Sridhar; Superior Pellucid Marginal Corneal Degeneration . Invest. Ophthalmol. Vis. Sci. 2002;43(13):154.
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Purpose:To report the clinical features and topographic findings of superior pellucid marginal corneal degeneration (PMCD) Methods:A retrospective chart review was done of ten eyes of five patients of superior PMCD. Detailed history, visual acuity at presentation, degree of astigmatism, slit lamp examination findings, topographic features and Orbscan findings were noted where available. Improvement in visual acuity with spectacles or contact lens correction, surgical procedure if any, and final visual acuity were analyzed. Results:Four patients were males and one was female. All cases were bilateral. The patients ranged in age from 35 to 48 years. All cases had isolated superior PMCD. The best corrected visual acuity ranged from hand motions to 20/30 and the astigmatism from 2 to 19.5 diopters. The degree of thinning varied from 30 to 90%. The extent of thinning was commonly seen between 10 and 2 o'clock positions. Ectasia was seen below the site of thinning in all the cases of superior PMCD. Topographic features including vertical corridor of reduced power, against-the-rule astigmatism and superior loop cylinder were seen in seven eyes. The loop cylinder extended to the horizontal meridians in four of the seven eyes. Orbscan was done in two eyes of one patient and revealed an area of increased elevation in relation to the best-fit sphere superiorly corresponding to the area of ectasia in both eyes. Further in the horizontal meridian, the corneal surface showed progressive depression from the centre to periphery, suggesting a sharper bend. The visual acuity improved with rigid gas permeable contact lens in six eyes and ranged from 20/400 to 20/25. Two eyes underwent surgical intervention (Peripheral annular graft=1 and Lamellar graft=1) Conclusion:Pellucid marginal corneal degeneration can occur superiorly. It should be considered in the differential diagnosis of superior ectatic disorders. The topographic findings of a vertical meridian of reduced power and superior loop cylinder, which depends on the site and extent of thinning, is diagnostic of superior pellucid marginal degeneration.Visual rehabilitation is usually possible with contact lenses and surgical mode of management may be required in selected cases.
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