Front Toric Reverse Geometry Scleral Lens Fit
on a Post-Radial Keratotomy and Post-Astigmatic Keratotomy Patient
A 51-year-old female reported for specialty lens fitting. She had a history of bilateral radial keratotomy (RK) surgery combined with astigmatic keratotomy (AK) in 1980. Lately, the patient complained of decreasing vision. She was interested in wearing contact lenses but had recently failed in them after an attempted fitting by another practitioner.
Figure 1 + 2
The patient’s visual acuity with new spectacles was OD +3.50 -1.25 X 003 20/40 (ghosting), OS +4.75 -2.25 X 040 20/40 (ghosting). Slit lamp exam showed bilateral RK/AK cuts without excessive wound gape or neovascularization (Figures 1 and 2). Topographies showed severely oblate corneas with mild irregularity (Figures 3 and 4).
Figure 3 + 4
The patient was diagnostically fit with 17.5mm scleral lenses (Boston XO). The lenses had 6 diopters of reverse geometry incorporated into PC 1. Lenses were dispensed with the following parameters:
Diameter/OZ 17.5/10.0 17.5/10.0
Base curve 43 diopters 45 diopters
Power -6.50 -8.00
PC1/w 7.26/1.45 6.98/1.45
PC2/w 10.0/0.9 10.0/0.9
PC3/w 13.0/0.9 13.0/0.9
PC4/w 15.0/0.5 15.0/0.5
Center thickness 0.49 0.49
The patient’s vision with the lenses measured OD 20/25 and OS 20/30 (shadowing). Her vision OS improved to 20/20 with an over-refraction of +0.50 -0.75 X 180. No lens flexure was evident with over-keratometry. A front-surface toric scleral lens was ordered with a power of -7.50 -0.75 X 180 for her left eye, which improved her vision to 20/20. At her last follow up she reported being happy with the comfort and vision that her scleral lenses (Figures 5 and 6) gave her, although she still experienced mild ghosting of her vision.
Figure 5 + 6
Summary & Discussion
Fitting severely oblate corneas with GP designs can be difficult. Scleral lenses are ideal for most of these patients because of their inherent stability. A reverse geometry scleral design helps to ensure an even corneal vault and to reduce risk of mid-peripheral touch. Any residual cylinder can be effectively corrected by using front surface toricity.
Greg DeNaeyer is a 1998 graduate of The Ohio State University College of Optometry. He completed a hospital based residency at the Columbus VA Medical Center. Greg joined Arena Eye Surgeons in 1999 and is currently the Clinical Director. His primary interest is specialty contact lenses.
Greg is the president of the Scleral Lens Education Society and is a Fellow of the American Academy of Optometry. He is a contributing editor for Contact Lens Spectrum and a contributor to Review of Cornea and Contact Lenses and Optometric Management. Currently his primary research is focused on profilometer designed scleral contact lenses, scleral lenses that correct higher order aberrations, and topical drug delivery devices. He has consulted for Visionary Optics, Essilor, Inspire Pharmaceuticals, B+L, and Aciont.