Clinical Findings and Management of Pellucid Marginal Degeneration Using Scleral Lenses Over INTACS and Corneal Collagen Cross-linking with Riboflavin

Abstract

This case study provides an analysis of an individual affected by pellucid marginal degeneration (PMD). This particular case demonstrates the effectiveness of new scleral lenses over a severe form of PMD that underwent corneal crosslinking (CXL) with riboflavin over intra-stromal corneal ring segments (INTACS). PMD is a rare, progressive, degenerative corneal disease typically characterized as peripheral, bilateral, and inferior ectasia producing a crescent shape. It has been found more commonly in males and appears between the second and fifth decade of life showing no signs of ethnic predilection. Although there is no evidence of the prevalence and etiology of PMD, it may be postulated that PMD is poorly differentiated because this disease is often confused or used interchangeably with keratoconus (KC). KC is a developmental anomaly in which a part of the cornea becomes thinner and bulges forward in a cone-shaped fashion as a result of non-inflammatory stromal thinning. KC is predominantly bilateral (90%) and according to recent studies demonstrates a prevalence of 2.3%. The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study found the genetic predisposition of KC to be at 13.5%, whereas other studies found it to be between 6–10%. This means most of those found having KC have no known association with the disease. More importantly, the cause of KC is still unknown. Regardless, the Federal Drug Administration (FDA) approval of KC treatment using CXL in April 2016 has shown excellent promise of improving the visual potential for patients with this progressive disease. This case demonstrates the usefulness of utilizing scleral gas permeable (GP) contacts over INTACS post CXL to provide optimal, stable vision, comfort and therapy. In addition, this paper shows an innovative way to utilize corneal topography to ensure proper fitting scleral lenses.