Lens Adhesion and RGP Daily Wear

BY ROBERT CAMPBELL, M.D. & PATRICK CAROLINE, C.O.T., F.A.A.O.
JAN. 1996

Lens adherence or binding is one of the most significant complications of RGP extended wear. Approximately 80 percent of patients experience occasional lens adherence upon awakening. However, this report describes a case of lens adhesion in an individual wearing RGP lenses on a daily wear basis.

WHEN SUCCESS GOES AWRY

Our patient is a 38-year-old female with a 16-year history of successful rigid lens wear. For the past two months she has experienced ocular dryness, a slight decrease in wearing time and spectacle blur. These symptoms gradually worsen toward the end of the day.

Slit lamp examination revealed bilateral, non-moving lenses with debris and mucus trapped beneath them (Fig. 1). Both lenses were displaced superior temporally with 1+ conjunctival injection OU. Fluorescein revealed minimal dye penetration beneath the center of the lenses. Manipulation of the lower lens edge broke the adhesive force allowing further diffusion of the dye, which produced a "fern leaf" pattern. After removing the lenses, we noted 360 degrees of corneal indentation with central punctate and peripheral arcuate staining (Fig. 2).

FIG. 1: PATIENT'S LEFT EYE SHOWING A BOUND RGP LENS. NOTE THE MUCUS TRAPPED BENEATH THE LENS.

FIG. 2: 360-DEGREE CORNEAL INDENTATION RING AND PUNCTATE STAINING IMMEDIATELY AFTER REMOVAL OF THE BOUND RGP LENS.

THE ETIOLOGY OF ADHERENCE

There are a number of hypotheses concerning the etiology of RGP lens adherence. These include lens suction or flexing effects, negative pressure effects, tear film mucous adhesion and lens care solution effects. The phenomenon is largely patient-dependent, and traditional lens design modifications may or may not resolve the adherence in individual cases.

The most accepted theory for lens adherence is proposed by Helen Swabrick, O.D., Ph.D., from the Cornea and Contact Lens Research Unit at the University of New South Wales, Australia. Her observations and studies indicate that adhesion results from a thinning or loss of aqueous tears that causes an increase in the viscosity of the post lens tear film. The resulting highly viscous layer of mucus-rich tears binds the lens to the corneal surface. The lens remains bound until the adhesion is broken (manually or with blinking) and the mucous film is diluted and thickened by aqueous tears. Dr. Swabrick's studies with fenestrated lenses show that negative pressure (a steep lens-to-cornea relationship) is not responsible for the adhesion, nor is lens flexibility (thinness) a major factor.

THE CARE PRODUCT IS THE CULPRIT

In reviewing our patient's care regimen, we learned that she had recently changed brands of lens care products. We advised her to return to the original system; she had no further episodes of lens adherence and she resumed her full wearing time.

As this case illustrates, it's important to monitor lens care products that may increase mucous response or decrease aqueous tear volume in individual patients. It's also important that you instruct individuals who wear their lenses overnight to observe lens movement upon awakening. Repeated occurrence of lens adherence that requires manipulation to free the lens may signal the need to discontinue extended wear. CLS

Dr. Campbell is medical director of the Park Nicollet Contact Lens Clinic & Research Center, Minnetonka, Minn. Patrick Caroline is director of contact lens research at Oregon Health Sciences University, Portland, Ore.