Deal with SEAL
BY TIMOTHY T. MCMAHON, OD, FAAO
SEAL stands for Superior Epithelial Arcuate
Lesion. In times past, practitioners have referred to this condition as "epithelial splitting" and "pseudodentrites." These lesions are almost
exclusively associated with soft lens wear. I haven't seen any
The lesions appear in the superior half of the cornea, very near or reasonably close to the limbus, and are arcuate in shape, hence the name of the condition. There is relatively little published data on this adverse event. It does not occur often; however, there is some suspicion that this problem may be more common with the new silicone hydrogel lenses. A recent poster presented at ARVO by O'Hare et al from the Cornea and Contact Lens Research Unit (CCLRU) in Sydney, Australia, indicates that SEALs form near the superior limbus with 71 percent occurring within 0.8mm of the limbus and 29 percent forming >0.8mm from the limbus.
Clinical findings associated with SEALs include a roughened epithelium that positively stains with sodium fluorescein and lissamine green. In most circumstances, there is no associated subepithelial infiltrate. However, I have seen a few chronically present cases that did develop subepithelial infiltrates and ultimately permanent anterior stromal scarring under-
neath the lesion.
What Causes SEALs?
Figure 1. Fluorescein stained Superior Arcuate Epithelial
Photo courtesy of Deborah F. Sweeney, PhD
The cause of SEAL formation appears to be mechanical in origin. A tight peripheral geometry seems to be the main culprit with the contact lens impinging on and grinding away at the epithelium. SEAL location indicates that the presence of the upper lid probably contributes to the event. Some initially thought that hypoxia contributes to SEALs. I believe their continued presence with silicone hydrogels does not support this view. Temporary lens cessation will permit the lesions to heal, typically without sequelae. As mentioned, scarring is rare. Refitting to a flatter base curve and/or changing the lens material usually solves the problem. Using a "softer" lens may achieve the same effect.
Silicone Hydrogel Wear
If SEALs occur more frequently with the new silicone hydrogel lenses than conventional hydrogel lenses, long-term management may be a problem. Silicone hydrogel lens base curve selection to date is limited (to one!), making fitting alterations impossible. For the present, move silicone hydrogel patients who develop SEALs into HEMA or glycerolmethacrylate products until more options are available. More base curve options for silicone hydrogel lenses would help address this and other fit-related problems.
Dr. McMahon is an associate professor and
Director of the Contact Lens Service at the
University of Illinois at Chicago Dept. of Ophthalmology & Visual Sciences.
Contact Lens Spectrum, Issue: July 2001