contact lens primer
Peripheral Corneal Desiccation
BY TIMOTHY B. EDRINGTON, OD, MS,
FAAO, & JOSEPH T. BARR, OD, MS, FAAO
Up to 90 percent of rigid contact lens wearers present with 3 and 9 o'clock staining (a.k.a. peripheral corneal desiccation). If the staining is coalesced and long-standing, dellen formation or scarring may result. Possible causes of 3 and 9 o'clock staining include incomplete blinking, inadequate spreading of tears by the lids and/or contact lenses and improper lens edge design.
The rigid contact lens patient with 3 and 9 o'clock staining will not necessarily have any symptoms. Often, the only complaint is intrapalpebral redness of the scleral conjunctivae. Because the area of corneal disruption is away from the visual axis, vision should not be adversely affected.
Staining will reveal superficial punctate keratitis (SPK) or coalesced staining, generally at the 3 and 9 o'clock position of the peripheral cornea. However, peripheral corneal desiccation may present at the 4 and 8 o'clock position or at the 6 o'clock position. The location is dependent on lens position. If lens movement is minimal, stippling can extend from the limbus to near the lens edge. If the lens consistently positions superiorly, the staining will occur inferiorly, as well as at the 3 and 9 o'clock location.
The 3 and 9 o'clock staining may be mild with only a few observable isolated stipples or more severe to the point of coalescing. Long-term peripheral corneal desiccation may lead to dellen formation or peripheral corneal scarring.
Management should be dictated by the eyecare practitioner's assessment of the cause. If incomplete blinking is identified as the possible cause, re-contour the edge profile to enhance comfort or increase the lens diameter to diminish lid-edge interaction. Also, educate the patient on the need for complete blinking.
A thin edge profile will optimize lid apposition to the cornea beyond the lens diameter, as well as allow the lid to more comfortably cross the lens edge. If peripheral clearance is excessive, the tear film adjacent to the lens edge may be disrupted, leading to areas of dryness. A steeper peripheral curve system might solve the problem and also allow you to prescribe a thinner lens profile to maximize lid apposition to the peripheral corneal surface.
Peripheral corneal desiccation is a fit-related, not oxygen-driven, condition. Increasing the Dk of the prescribed lens without changing the fitting characteristics will not alleviate 3 and 9 o'clock staining. However, a material that wets well, such as a fluorosilicone acrylate RGP material, may encourage comfortable blinking and help maintain a good tear film.
A Quick Fix
Maintaining a moist peripheral corneal environment should minimize or eliminate 3 and 9 o'clock staining. Contact lens re-wetting drops may be used to keep the peripheral cornea moist.
Soft lens patients do not present with 3and 9 o'clock staining because of the large overall diameter of the soft lens, which drapes the cornea preventing excessive areas of peripheral corneal drying. Soft lenses may be prescribed if RGP lens design changes do not resolve or minimize the staining. For patients who need rigid lenses to obtain satisfactory vision, such as keratoconus patients, a soft lens may be temporarily prescribed for wear beneath the rigid lens. You may also consider a rigid lens design with a larger diameter to cover the entire cornea.
Dr. Edrington is a professor at the Southern California College of Optometry. E-mail him at firstname.lastname@example.org.
Dr. Barr is editor of Contact Lens Spectrum and assistant dean of Clinical Affairs at The Ohio State University College of Optometry.