The Contact Lens Never Dispensed

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

A wide range of traumatic surgical or disease-related conditions can result in an irregular corneal surface.

The following signs will help you identify irregular corneal astigmatism: 1.) irregularity or doubling of the lower right keratometric mire; 2.) distortion of projected corneal images such as photokeratoscopy, video keratoscopy rings or grids; 3.) identification of the videokeratoscopy CIM (Corneal Irregularity Measure) or SRI (Surface Regularity Index); or 4.) scissoring motion of the retinoscopy reflex.

Irregular astigmatism within the pupillary margin often results in a loss of best corrected spectacle acuity. In such cases, a rigid contact lens can effectively neutralize the anterior corneal astigmatism and significantly improve visual acuity.

This month, we review the use of a diagnostic rigid lens refraction to determine an individual's best corrected visual acuity. Our patient is a 26-year-old female with a five-year history of extended wear disposable lenses. She was a bilateral -8.00D myope who wore her seven-day disposable lenses for 30 days with monthly lens removal and disposal OU. Ten months ago, she experienced a foreign body sensation, conjunctival injection and cloudy vision in the right eye only. She was diagnosed as having three spontaneous corneal ulcers that were treated aggressively with appropriate antibiotic therapy.

Recent slit lamp examination revealed one dense, paracentral ulcer within the visual axis and two fainter ulcers mid-peripherally at 1 o'clock and 6 o'clock (Fig. 1). The corneal epithelium and sensitivity were intact over the ulcer sites. Stromal scarring was noted within the anterior 50 percent of the cornea. The anterior chamber and crystalline lens were clear. The left eye was normal.

FIG. 1: CORNEAL SCARS SECONDARY TO INFECTIOUS KERATITIS.

FIG. 2: IRREGULAR ASTIGMATISM AS NOTED BY PHOTOKERATOSCOPY.

FIG. 3: FLUORESCEIN PATTERN OF THE DIAGNOSTIC RIGID LENS.

Manifest refraction OD was -8.50 -1.50 x 20 degrees with a visual acuity of 20/100. Quantitative photokeratoscopy revealed that a base curve of 7.90mm 42.75D would provide optimal mid-peripheral contact along the horizontal meridian (Fig. 2). We fitted a rigid lens, base curve 7.90mm 42.75D -3.50D 9.5 diameter (Fig. 3). A sphero-cylinder refraction revealed an overcorrection of -4.00 sphere and visual acuity of 20/50-.

The rigid lens refraction illustrated to the patient the visual potential of her eye without surgical intervention. After considering all options, the patient chose to undergo lamellar keratoplasty. Due to the 50 percent depth of the scarring, excimer laser PTK was contraindicated.

A rigid lens refraction should be part of any comprehensive workup of individuals with irregular corneal astigmatism. This information, combined with slit lamp evaluation of scar location and depth and retinal function testing, helps provide the framework to advise patients of the appropriate treatment options.

This case also illustrates the need to reiterate to patients the importance of compliance in all contact lens wear. This patient's 30-day extended wear far exceeded the recommendations of her doctor and the lens manufacturer. 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, Portland, Ore.