Reverse Geometry Design For A Post-LASIK Patient
contact lens case reports
Reverse Geometry Design
For A Post-LASIK Patient
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
Patient R.Y. underwent LASIK surgery to his right eye only in September 1998. His preoperative refractive error OD was -15.00 -4.25 x 25, with a best corrected visual acuity of 20/25.
Since his initial surgery, he has undergone two enhancements resulting in an uncorrected VA of 20/200, correctable to 20/100 with a manifest of +1.50 -3.00 x 46. He continues to wear an RGP lens on his
unoperative left eye, 43.25 -12.00/9.2/7.8 OZ, with a corrected VA of 20/25. Post LASIK K readings OD were 31.50@36/ 33.50@126 with 2+ distortion and OS 43.50@160/ 45.00@70 (Figure 1). Cross-sectional Scheinpflug photography shows the amount of tissue ablated from the right eye (Figure 2) vs. the unoperated eye (Figure 3).
Figure 1. Photokeratoscopy of the patient's post-LASIK right eye and his unoperated left
Figure 2. Scheinpflug photography of the post-LASIK right
Figure 3. Scheinpflug photography of the normal, unoperated left eye.
Traditional and reverse geometry RGPs failed due to excessive decentration and/or persistent bubbles beneath the lens. The patient was eventually trial fitted with a 14.5mm RGP MarcoLens manufactured by C&H Contact Lens in Dallas. A diagnostic lens of 42.50/ plano/14.5mm provided an excellent scleral fitting relationship; however, a large bubble remained fixed beneath the center of the lens (Figure 4).
Figure 4. Traditional MarcoLens
Figure 5. Reverse geometry
Marco-Lens design OD.
This was easily remedied by ordering the MarcoLens with a central reverse geometry design. The final lens specifications were base curve 34.50 (9.78mm,) power -2.50, diameter 14.5mm with a mid-peripheral curve of 42.50 (8.04mm) (Figure 5). The lens was manufactured in Fluoroperm 60 material. Today the patient enjoys a comfortable 14- to 16-hour wearing schedule and a stable VA of 20/30.
Many patients have benefited from the large diameter Marco-Lens design. The ability to support the lens on the more regular scleral curve helps to overcome frequent lens decentration problems associated with traditional spheric or aspheric corneal lens designs.
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.
Contact Lens Spectrum, Issue: July 2000