Scleral Lenses &
Lynette Johns OD FAAO FSLS
Schornack et al. reviewed the fits and topographies of 54 eyes wearing standard Jupiter scleral lenses for dry eye conditions or keratoconus.1 While there was a loose correlation between the reference sphere and the steep and flat keratometry readings, they concluded that diagnostic fitting may still be required. When fitting scleral devices, topographers may not provide a valuable measurement for starting the fitting; however, they can be a great asset to guide care during and after the fitting.
We fit scleral devices on a 44-year-old keratoconus patient wearing very flat-fitting corneal (R)GP lenses over piggyback soft contact lenses. Her vision with the piggyback lenses was 20/30+2 OD and 20/30-2 OS. There were multiple anterior subepithelial elevated opacities OS>OD. Initial topographies showed central irregularities inconsistent with typical keratoconus patterns.
The scleral devices were well-vaulting (>400 micron) and provided adequate room for her corneas to unmold. Diagnostic devices with varying amounts of front-surface eccentricity (FSE) were trialed. The right eye accepted 0.8 FSE (7.9 base curve, +3.00 power), and the left accepted 0.6 FSE (7.9 base curve, +3.00 power) to optimize the acuity. Her initial acuity was 20/30+2 in both right and left eyes with her devices. With the same lenses two weeks later, the acuity changed to 20/50-1 OD and 20/50-2 OS. She rejected optical FSE at that visit (OD: 7.9 base curve, +1.00 power; OS: 7.9 base curve, +0.25 power). Her second pair of devices corrected her to 20/25-2 OD and 20/30-1 OS, and the fit remained the same. The topographies from that visit suggested steepening of the ectasia, but still an irregular pattern.
Four months later, the topographies demonstrated a more traditional keratoconus pattern, suggesting that the corneas had unmolded from the flat-fitting corneal (R)GP lenses. Her acuity measured 20/30 OD and 20/50 OS. She accepted 0.8 FSE in both eyes (OD: 7.9 base curve, +2.25 power; OS: 7.5 base curve, +2.75 power), and she achieved 20/30+2 OD and 20/30 OS with less ghosting. The vault was narrow over her left cornea, requiring a 200 micron increase.
Right eye initial (top), after 2 weeks (middle) and
four months (bottom)
Our office uses diagnostic trial devices to begin our fits. We do not use topography as a starting point, but we order one for all of our ectasia and post-transplant cases. In this case, topographical changes may explain the vision fluctuation that we observed with the same device between visits. Perhaps the changes in her topographies altered her higher-order aberrations through the device. If we had waited for the corneal topography to stabilize, we may have reduced the number of devices we dispensed. However, that would have compromised her visual functioning during the unmolding process, and she may have returned to her corneal lenses. Topography served as a great educational tool for the patient and provided reassurance and an explanation of her visual experience.
The changes in vision and topography prompted us to trial different optics to enhance her vision during the corneal unmolding process. The final powers varied with different amounts of asphericity, indicating the need to use trial lenses with FSE combined with over-refractions to determine the best acuity and optical quality for the patient. Aspheric optics may enhance the vision of patients wearing devices for ectasia.2
Left eye initial (left), after 2 weeks (middle) and four months (right)
Dr. Lynette Johns has been the senior optometrist at the Boston Foundation for Sight since 2005.
She is a graduate of the New England College of Optometry where she completed a residency in cornea and contact lenses. She is adjunct clinical faculty at the New England College of Optometry.
Dr. Johns is a fellow of the American Academy of Optometry and a fellow of the Scleral Lens Education Society.