New Keratoconus Lens Gains
High Marks

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

Few clinical conditions are more challenging to contact lens practitioners than keratoconus. The management of this condition with contact lenses dates to early-1888 when French ophthalmologist Eugene Kalt designed a crude glass shell to "compress the steep conical apex."

Since then, a wide variety of contact lens designs and fitting techniques have been proposed for keratoconus, most enjoying only limited success. Today, the condition can be managed adequately with contact lenses thanks to advances in topographical assessment techniques (photokeratoscopy and videokeratography), as well as advances in lens designs, materials and manufacturing techniques.

LENS AWARENESS
DECREASES WEAR TIME

This month's case history describes a 32-year-old male with a 10-year history of moderate keratoconus OD and early keratoconus OS. He had enjoyed great success with his RGP correction until recently when he reported symptoms of lens awareness OD. Maximum wearing time OD had decreased to five or six hours a day with normal all-day wear OS. He had seen two excellent contact lens practitioners and had been unsuccessful with numerous lens designs and materials.

The patient presented to our clinic with central keratometric readings of: 54.62 x 18 degrees/57.00 x 108 degrees OD, 46.75 x 146 degrees/49.50 x 56 degrees OS. We performed photokeratoscopy and video keratography OD (Figs. 1 & 2). The patient's right eye was fit with the new Rose K design lens, base curve 6.20 (54.50D), power -12.00, diameter 8.7, and he immediately reported improved comfort. The fluorescein pattern revealed relative alignment across the apex of the cone with mild mid-peripheral bearing and excellent peripheral clearance (Fig. 3). The patient returned to full-time wear.

FIG. 1: PHOTOKERATOSCOPY OF THE RIGHT EYE.	FIG. 2: VIDEOKERATOGRAPHY OF THE RIGHT EYE ILLUSTRATING PARACENTRAL TEMPORAL STEEPENING WITH SIGNIFICANT SUPERIOR NASAL FLATTENING.
FIG. 3: FLUORESCEIN PATTERN OF THE ROSE K DESIGN ON THE PATIENT'S RIGHT EYE.

KEY: CONTROL PERIPHERAL LENS CLEARANCE

The Rose K keratoconus fitting system, designed by Dr. Paul Rose of Hamilton, New Zealand, is distributed in the United States by Lens Dynamics in Lakewood, Colo. The posterior geometry of the Rose K is best described as a floating optical zone diameter which decreases as the lens radius steepens. The peripheral lens design is calculated independently for each central radius of curvature. The lens periphery can be independently steepened or flattened, depending upon the individual peripheral corneal topography.

To date, we've evaluated the Rose K design on 30 keratoconus patients symptomatic with their present contact lenses. It's our impression that this system offers advantages over previous keratoconus lens designs. With its 26-lens diagnostic set and the ability to independently adjust peripheral lens clearance (in a controlled fashion), this fitting system should be a valuable addition to contact lens practice for anyone involved in managing these challenging patients. 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.