continuous wear colloquy
Epithelial Splits Don't Always Cause a "Frown"
BY LORETTA B. SZCZOTKA-FLYNN, OD, MS, FAAO
First-generation silicone hydrogel contact lenses have brought about renewed interest in some mechanical lens complications. Similar to the mechanical effects that resulted from lathe-cut, high-modulus lenses from years past, silicone hydrogel lenses can cause corneal findings that relate to the stiffness of these materials.
One such mechanical event is an epithelial split, often called a superior epithelial arcuate lesion (SEAL). You'll usually find this thin, arcuate, frown-like lesion within 1mm to 3mm of the superior limbus between 10 o'clock and two o'clock in an area that the upper eyelid normally covers. SEALs have significant overlying staining and possible underlying diffuse infiltrates.
Figure 1. A thick toric lens caused this "smile"-like epithelial split.
Treating and Preventing SEALs
Most clinicians consider an epithelial split a mild or a "non-significant" adverse event. The most common symptom is foreign body sensation or irritation. Instructing the patient to simply stop lens wear for a few days usually heals the split in the epithelium, although the recurrence rate is high and may prevent him from continuing in the same lens.
Proper patient selection may prove the best prevention. Epidemiological risk factors include steep corneas, tight eyelids and Asian eye shape, so be cautious when beginning silicone hydrogel continuous wear with such patients, especially if they have a previous history of SEALs.
Resolving Recurring SEALs
If your patient presents with a SEAL during continuous wear with silicone hydrogel lenses, then first try changing the base curve if this option exists. For example, refit from 8.6mm base curve to 8.4mm base curve in Night & Day (CIBA Vision) lenses, or vice versa.
Switching to another silicone hydrogel lens material often easily solves the puzzle. For example switch from Night & Day to PureVision (Bausch & Lomb), which will be available in the United States again in April 2005, or vice versa. Or switch to the new O2Optix lens (CIBA), which has a lower modulus of elasticity than the Night & Day lens and may reduce mechanical chafing.
Lastly, if all silicone hydrogels fail for a continuous wear patient, then I usually recommend daily wear with softer materials (such as Acuvue Advance [Vistakon] or low-Dk polymers) rather than recommending extended wear with low-Dk materials.
Turn that Frown into a Smile
No definitive, widely accepted etiology for epithelial splits exists. However, clinicians believe that they result from mechanical stress from chafing and rubbing of the cornea beneath a stiff lens material and the patient's lids.
The splits almost always occur in the superior cornea, but they can form anywhere on the cornea where significant lens-to-cornea interaction occurs. In fact, I recently observed an inferior epithelial arcuate lesion that resulted from a thick soft toric lens, which reminded me that this phenomenon isn't unique to silicone hydrogel lens wear. Presumably, the thick, prism-ballasted portion of the soft toric lens created an epithelial split beneath the thickest area of the lens, in the inferior third of his cornea, creating a smile-like pattern (Figure 1).
Dr. Szczotka-Flynn is an associate professor at Case Western Reserve University Dept. of Ophthalmology and is director of the Contact Lens Service at University Hospitals of Cleveland.