contact lens case reports
Epithelial Microcysts in an Extended Wear Patient
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRE, FCLSA
APRIL 1998
Through the years, clinicians have come to appreciate the diverse spectrum of responses to corneal hypoxia resulting from the overnight wear of contact lenses. Responses can range from barely detectable or theyrneal thickness, epithelial microcysts, vertical striae, folds in Descemet's membrane and endothelial
from undetectable edema to increases in corneal thickness, epithelial microcysts, vertical striae, folds in Descemet's membrane and endothelial polymegethism. Most practitioners agree that current soft lens materials that are approved for extended wear are best suited for daily wear only. During overnight wear, the lenses lack the movement, biocompatibility and oxygen transmissibility necessary to avoid adverse responses. New generations of high Dk extended wear RGP and soft lens materials, including the surface-treated silicone-hydrogel materials, are on the horizon.
Extended Wear Without Follow-up Care
Patient S.H. is a 36-year-old man with a 14-year history of soft contact lens wear. He had been wearing -4.75D extended wear lenses for the past three years on a weekly disposable regimen, and had been purchasing them from an outside source. In his first eye exam in two years, S.H. presented free of ocular symptoms with a corrected visual acuity of 20/20 OU. The most remarkable slit lamp finding was the presence of numerous midperipheral epithelial microcysts (Fig. 1).
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These small, translucent interepithelial cysts initially form at the level of the basal epithelial cells following about three months of extended wear. On indirect retroillumination, the lesions appear as fine, round vesicles which are uniform in size and shape. They are thought to be comprised of disorganized basal cells, the walls of which have been compromised by prolonged corneal hypoxia. The microcysts eventually migrate toward the surface and break through the epithelium. Expulsion of the microcysts results in small, round epithelial defects which can be detected easily with fluorescein (Fig. 2). You can determine the degree of hypoxia experienced during extended wear by quantifying the level of microcyst development. The fact that microcysts take several months to develop and to disappear after discontinuing lens wear suggests that some alteration in corneal epithelial function occurs.
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Abandoning Extended Wear
Management options include: discontinuation of lens wear until the cornea is totally clear, careful management with high Dk/L daily wear lenses or continuation of extended wear with close observation of the microcysts. We advised S.H. of the possible complications with prolonged corneal hypoxia, especially in the presence of chronic epithelial defects. We switched him to a strict regimen of daily disposable lenses, and told him that extended wear materials that can satisfy his oxygen requirements may become available in the future.
Patrick Caroline is an assistant professor of ophthalmology at the Oregon Health Sciences University and an assistant professor of optometry at Pacific University. Mark Andre is director of contact lens services at the Oregon Health Sciences University.