prescribing for astigmatism
Reconsidering the Status Quo
BY JULIE A. SCHORNACK, OD, MED
It was inevitable from the moment silicone hydrogels entered the contact lens market that it was only a matter of time before manufacturers moved from "sphere only" options into more advanced lens designs. Today, all of the physiological benefits that come with spherical silicone hydrogel lenses are available to many of our astigmatic patients as well.
Time for an Upgrade
Human nature usually prompts us to stick with a habitual contact lens option that works for our patients. Rejecting something that works seems counterintuitive somehow.
I think the challenge on the table is to force yourself to upgrade currently successful hydrogel toric lens wearers into silicone hydrogel toric lens designs. I believe sticking with the status quo is simply not good enough. The undeniable physiological benefits are difficult, if not impossible, to ignore. Usually a simple and quick explanation to patients concerning the benefits of upgrading to a silicone hydrogel toric contact lens is all that's needed to initiate a new contact lens fitting.
Historically, some of the stabilization methods in low-Dk hydrogel toric lenses contributed to an increased differential thickness in specific portions of the contact lens. In retrospect, we often found that the areas of increased lens thickness in low-Dk hydrogel toric lenses led to signs of corneal compromise. The cornea could show evidence of localized corneal edema, corneal neovascularization, epithelial staining and even topographical changes.
With the advent of silicone hydrogel contact lenses and the substantial increase in Dk they offer, the thickness differential associated with some stabilization methods becomes less significant. I believe this lends credence to the need to move traditional hydrogel toric patients into silicone hydrogel toric lens options to decrease or eliminate such oxygen-related complications.
The availability of fitting sets that address the majority of your patients' astigmatic needs has made upgrading patients to silicone hydrogel toric lenses infinitely simpler. Nothing is more powerful than being able to instantly fit a patient with the appropriate silicone hydrogel toric lens for a test drive once he verbally agrees about the benefits of upgrading.
Taking a New Approach
Although in the past for low amounts of astigmatism (about 0.75D) I would potentially prescribe a spherical equivalent power or an aspheric soft lens design, I now aggressively pursue silicone hydrogel toric lens designs. Re-producibility and stability of toric contact lenses has progressively improved over time, resulting in a generation of silicone hydrogel toric lenses that provides superior visual performance. Some recent studies that affirm this stance have highlighted patient preferences for soft toric lens options over aspheric lens designs even for low amounts of astigmatism.
Even with the fitting sets that satisfy most astigmatic patient needs, some patients will inevitably have refractive errors that fall outside of the limits of most silicone hydrogel toric lens offerings. Keep in mind that patients who have higher spherical and cylindrical powers now have a made-to-order silicone hydrogel option available. You should always present this option to such patients when appropriate, because it's often this patient base who would benefit most from the superior oxygen transmission that a silicone hydrogel lens material provides.
Make the Switch
Many compelling factors make silicone hydrogel toric lens options desirable as the first choice modality for your patients who have astigmatic needs. Your toric patients will appreciate your desire to provide them with a lens that will ensure superior corneal physiology and successful visual performance with a premium material. CLS
Dr. Schornack is the associate dean of Clinical Education and serves in the Cornea and Contact Lens Service at the Southern California College of Optometry.