contact lens case reports
Semi-Scleral Lenses and Post-Refractive Surgery Patients
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
In recent years a family of optical and therapeutic lenses has emerged into the marketplace called high-Dk semi-scleral lenses. These rigid lenses, designed to fit beyond the limbus, range in diameter from about 13.0mm to 18.0mm. Practitioners have used semi-scleral lenses to manage a wide range of ocular disorders including post-refractive surgery complications. Great strides have been made in refractive surgery, but ocular surgery and its inherent complications may leave some with suboptimal visual results.
A case in point is a female patient who underwent bilateral automated lamellar keratoplasty (ALK) in 1994. She subsequently developed an epithelial in-growth within the cap interface of her left eye. The cap was lifted and scraped multiple times. She went on to develop a post-ALK ectasia of the left eye (Figure 1).
At her initial visit her central keratometric readings were OD 42.37 @ 007/43.87 @ 097 and OS 44.87 @ 146/48.62 @ 056 with an apical radius of curvature of 54.00D, 6.25mm. Her entering VAs were OD 20/20 with a spectacle Rx of –2.75 –1.75 x180 and OS 20/100 with –1.25D sphere. Right eye slit lamp examination revealed a clear cornea with a residual scar at the ALK cap interface. The left eye showed a mild central stromal scar surrounded by 4mm of diffuse stromal haze.
Figure 1. Corneal topography post-ALK OU.
Historically, she had failed with a number of GP and soft lens designs and had the most success with a scleral lens design. She successfully wore the scleral lens for about four years. However, early this year she discontinued the lens due to increasing discomfort. At that time we refit the patient into the Jupiter Lens design (Medlens Innovations, Inc.).
Fitting semi-scleral lenses begins with selecting a diagnostic lens with a base curve radius equal to the radius of the steepest keratometric reading. Fluorescein is placed onto the posterior surface, and the lens is inserted onto the eye. The ideal fitting relationship should exhibit corneal vaulting and alignment in the area of the sclera curve. The final specifications of the patient's left lens were base curve 47.00D (7.20mm), –9.37D power, 0.39mm center thickness, 8.2mm optic zone and an overall diameter of 18.2mm (Figure 2). Her visual acuity with the semi-scleral lens was 20/40+ and wearing time is currently 14 to 16 hours a day.
Figure 2. Semi-scleral lens on the patient's left eye.
Tapping the Potential
This case illustrates how you can use the new generation of high-Dk semi-scleral lenses to manage a number of optical and comfort issues often associated with more traditional corneal lens designs.
We believe that with advancements in scleral lens manufacturing, materials and a greater understanding of fitting techniques that the full potential of these lenses will emerge. CLS
Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision and SynergEyes, Inc.