Contact Lens Design & Materials
Scleral My Dry Eye
BY DAVID L. KADING, OD, FAAO
Specialty contact lenses are not always prescribed simply to improve clarity of vision—they are occasionally indicated for managing other conditions as well. Up until recently, only a small number of specialty contact lens practitioners were fitting scleral lenses, despite the fact that several decades of peer-reviewed reports in the literature indicate the therapeutic benefits of scleral lenses. Patients who have severe ocular surface disease, such as keratoconjunctivitis sicca, may also benefit from wearing scleral lenses as a protective medical device.
How Scleral Lenses Can Help Dry Eye Patients
Dry eye patients can suffer from debilitating ocular discomfort; scleral lenses can provide both comfort and incredible relief. There are two main hypotheses to explain why this is the case.
A scleral lens is designed such that a reservoir of fluid sits between the contact lens and the corneal surface (Figure 1). Therefore, the first hypothesis is that the fluid layer acts as a protective moisture layer for a compromised epithelium, providing constant moisture to the ocular surface in addition to neutralizing the refractive error.
Figure 1. Optic section view (left) and side profile view (right) of the scleral lens fluid reservoir that bathes the dry eye throughout the day.
Second, the large scleral shell covers the entire cornea and protects it from exposure to the air. Environments in which a patient will most notice the benefit of this protection are in windy outdoor conditions as well as in buildings, cars, and other places in which there is artificial air circulation. Regardless of ocular surface status, most patients find scleral lenses very comfortable upon application.
The ocular surface and quality of tears in dry eye patients usually does not provide a smooth surface for good optics. This results from the instability of the tear film and often also from epithelial defects or other corneal insults that cause roughness on the surface of the eye. The fluid layer held between a scleral lens and the eye smooths out these defects to create a better refractive surface, so visual acuity in such patients can often also be improved as compared to spectacle correction.
Choose Your Filling Solution Wisely
At present, the only solution approved by the U.S. Food and Drug Administration for use with scleral lenses is preservative-free saline. Because the solution in the reservoir typically remains behind the lens with little tear exchange during wear, it is important to not use other solutions that may contain preservatives or other components that would be toxic to the cornea with extended exposure. This is important for any patient, but even more so for dry eye patients whose ocular surface is already uncomfortable and compromised.
A Tool for Severe Dry Eye
When scleral lenses are used therapeutically, they can be of great benefit to dry eye patients. It is important to consider them when managing patients who have a compromised ocular surface. CLS
Dr. Kading owns the Specialty Dry Eye and Contact Lens Center in Seattle. He is the co-owner of Optometric Insights with Dr. Mile Brujic. He has received honoraria for consulting, performing research, speaking, and/or writing from Alcon Laboratories, Allergan, Bausch + Lomb, Biotissue, Contamac, Essilor, Nicox, Oculus, RPS Detectors, TearScience, Valley Contax, and ZeaVision. Follow him on Twitter @davekading.