Article Date: 5/1/2003

contact lens case reports
Fitting Contact Lenses After RK Surgery
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO

Figure 1. Patient's post radial keratotomy corneal topography.

Over the past 30 years, millions worldwide have undergone radial keratotomy to correct refractive error. While some have enjoyed a functional outcome, others require supplemental vision correction. In the event of a sub-optimal surgical result, the patient is faced with three corrective options: glasses, contact lenses or additional refractive surgery.

Today we have a wide range of contact lens modalities, many designed specifically for the post-refractive surgery cornea. They include spherical and aspheric gas permeable (GP) and soft designs, reverse geometry GP and soft designs and large diameter 15.00mm (semi-scleral) GP designs. We successfully managed a patient intolerant to GP lenses with a new aspheric, reverse geometry, toric soft lens design manufactured by Innovations In Sight.

Figure 2. The aspheric, reverse geometry soft lens design.

Poor RK Result

SZ is a 24-year-old female who underwent bilateral radial keratotomy in November 1998. Her pre-op refractive error was about ­5.00D OU. Today, her manifest refraction is OD +1.50 ­1.50 x 150 20/20 and OS +4.75­-4.00 x 20 20/25. K readings are OD 38.25 @172 /40.37 @ 82 (2+ distortion) and OS 35.50 @ 004 / 39.12 @ 94 (1+ distortion) (Figure 1). She was fit with several spherical and reverse geometry GP designs; however, she was unable to fully adapt to the lenses.

Figure 3. Patient's right and left eye with the reverse geometry soft lenses.

We then fit her with the reverse geometry soft lens design. This lens incorporates a flat central radius of curvature, 9.70mm, to align the flatter central cornea and a steeper mid-peripheral zone of 8.30mm, 8.60mm or 8.90mm to align the "more normal" mid-peripheral cornea (Figure 2). We tried diagnostic lenses with a 9.70mm central base curve , an 8.60mm mid-peripheral fitting curve and a 14.5mm overall diameter. Following equilibration, we evaluated the lens-to-cornea fitting relationship and performed a sphero-cylinder over-refraction. We ordered the following lenses: OD 9.70/8.60, +1.50 ­1.50 x 150, 14.5mm diameter and OS. 9.70/8.60, +4.75 ­4.00 x 20, 14.5mm diameter. The lenses were ordered with a center thickness of 0.25mm to mask the irregular astigmatism. Anterior aspheric optics were used to manage the spherical aberration and coma induced by the surgery. Ultimately, the patient's visual acuity with the lenses was 20/20 OU and stable throughout her 16-hour day.

Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University. Mark André is director of contact lens services at the Oregon Health Sciences University and an adjunct professor of optometry at Pacific University.

 


Contact Lens Spectrum, Issue: May 2003