When Tinted Lenses Make an Unwanted Impression

BY ROBERT CAMPBELL, M.D. & PATRICK CAROLINE, C.O.T., F.A.A.O.
FEB. 1997

Tinted and opaque hydrogel contact lenses have been in existence for more than 10 years. Throughout that time, the lenses have performed well with only a few minor complications, such as subjective peripheral field changes, difficulties in dim illumination, symptoms of dryness and -- the topic of this month's case history -- annular corneal imprints.

A GENERAL COMPLAINT OF
PERIODIC OCULAR DRYNESS

Patient K.N. is a 28-year-old woman who had worn opaque lenses successfully for one year. Her lens specifications were OD 8.6mm base curve, -3.50D power, 14.5mm diameter; OS 8.6mm base curve, -4.00D power, 14.5mm diameter. Her present lenses were three months old.

Visual acuity with the lenses was 20/20 OU and wearing time was 10 to 12 hours a day. She used a multipurpose lens care regimen for nightly cleaning and disinfection.

The patient's chief complaint was periodic ocular dryness, which did not resolve when she used preservative-free lubricants.

Slit lamp examination showed that both lenses moved and centered well (Fig. 1). Manual push-up test showed no evidence of a tight lens. Fluorescein examination after lens removal revealed bilateral five-millimeter annular corneal imprints identical in size and location to the clear (non-tinted) portion of the soft lens (Fig. 2).

FIG. 1: PATIENT K.N. WITH A WELL-CENTERED OPAQUE LENS.

FIG. 2: CENTRAL FLUORESCEIN POOLING AND IMPRESSION RING.

We instructed the patient to stop wearing her lenses and to return the next day for examination. After 24 hours, both rings had completely resolved.

TINTED VS. NON-TINTED =
DIFFERENCES IN HYDRATION

Corneal imprint rings associated with opaque hydrogel lenses are not a new phenomenon. Clements et al. first described this in the June 1988 issue of Contact Lens Spectrum. The finding is not unique to opaque lenses, but has been noted in all tinted hydrogel lenses that have clear, non-tinted central zones. The rings may be related to differences in the hydration properties of the tinted and the non-tinted zones of the lens.

The tinting dyes on the anterior surface may cause a localized reduction in water content. This change can result in differing pressure forces between the cornea and the tinted and non-tinted zones of the lens.

Corneal impression rings appear to represent a minor complication associated with tinted and opaque lenses. In our case, the patient had been experiencing transient symptoms of ocular dryness, which may have been lens-induced, solution-induced or physiologic.

We prescribed standard clear lenses on a frequent replacement schedule and a preservative-free disinfection system. The rings resolved and the symptoms of ocular dryness improved dramatically.

A number of unanswered questions remain regarding this patient. Would the impression rings have resolved if we had refit the patient into another brand of opaque lens? And what was the role of the multipurpose lens care regimen in exacerbating the dry eye symptoms? In other words, would the impression rings have resolved if the patient had switched to a preservative-free lens care regimen? In our haste to resolve the patient's problems, we did not address these questions. CLS

Dr. Campbell is medical director of the Park Nicollet Contact Lens Clinic & Research Center, Minnetonka, Minn. Patrick Caroline is an assistant professor of optometry at Pacific University, Forest Grove, Ore., and director of contact lens research at Oregon Health Sciences University in Portland.