20/10 Vision for a Keratoconus Patient
Greg Gemoules, OD
Coppell, TX (USA)
For a decade and a half, our practice has been visited by patients with complicated corneal conditions. Our main form of treatment has always been therapeutic (R)GP lenses. Over time, our fitting strategy evolved from corneal lenses to corneal-scleral lenses and ultimately to scleral lenses. To better understand what our patients were seeing, we acquired a wavefront aberrometer (iTrace from Tracey Technologies, Houston, Texas) in 2006.
Late 2007, we began using time-domain OCT scans of the anterior eye to design custom scleral lenses. The ultra-stable and non-rotational nature of these lenses seemed like an ideal vehicle for complex optics. In late 2010 or early 2011, we began experimenting with wavefront-guided scleral lenses. This work has culminated into several U.S. patents. We design the optics in-house using Zernike coefficients and other proprietary techniques based on the aberrometry measurements. The lenses are manufactured by Truform Optics, Euless, Texas.
Today, we are using ultra-sophisticated computer-aided design software from Dassault Systemes (Vélizy-Villacoublay, France) and Inceptra (Pembroke Pines, Florida) that has been customized for our particular needs. We are also working with newer OCT technology, and we can design lenses from virtually any kind of image file using any imaging technology.
In 2011, we compiled our early experiences with these lenses. In a cohort of 52 eyes of 26 patients, only 36% were correctable to 20/20 with conventional spectacles. When scleral lenses with standard sphero-cylindrical optics were used, 50% were corrected to 20/20 or better. When we applied wavefront-guided surfaces, the numbers vastly improved, with 75% achieving 20/20 or better acuity. Rather surprisingly, 16% of eyes achieved a visual acuity of 20/10 with wavefront-guided optics. An example of this kind of a result is presented here.
A 29-year-old gentleman was referred to our clinic by a local LASIK surgeon who declined to perform LASIK on him because of irregular corneal topographies. Our examination revealed an obvious case of moderate keratoconus in the right eye and mild keratoconus in the left.
His unaided visual acuities were 20/60 in the right eye and 20/30 in the left. With 4.5D of astigmatism in the right eye and 2.0D in the left, he was correctable to 20/30 in the right eye and 20/20 in the left with spectacles. LASERFIT lenses with standard sphero-cylindrical optics to correct the lower-order aberrations resulted in only 20/30 acuity in the right eye. A LASERFIT lens with wavefront-guided optics improved the quality of vision in his worse right eye to 20/15, while the left eye could identify 20/10 letters.
The table above shows the improvement in the higher-order aberrations with standard optics and then with wavefront-guided optics. The LASERFIT process with wavefront-guided optics typically can result in an additional reduction of the higher-order aberrations in the range of 30%-70%
In summary: wavefront technology improves higher order aberrations and visual acuity over the sphero-cylindrical optics in the majority cases, but results can and do vary.
Figure 1. Refraction maps of the right eye wearing the regular sphero-cylindrical lens (top) and the wavefront lens (bottom). Units are in 1.25D. The wavefront lens produces a flatter and smoother refraction across the entrance pupil.
Greg Gemoules received his optometry degree from the Illinois College of Optometry (USA). He moved to Texas and established his practice in Coppell, a growing suburb of Dallas (USA). He has established a large specialty lens practice and has several publications in the peer-reviewed literature. He is a pioneer in the use of optical coherence tomography (OCT) and wavefront-guided optics in the fitting of scleral lenses and has lectured at a number of conferences on the topic.