prescribing for astigmatism

The Boom in Frequent Replacement Torics

BY THOMAS G. QUINN, OD, MS
JUNE 1998

How often have you had to tell an astigmatic patient that disposable or frequent replacement soft contact lenses are not an option available to him? Those days are in the past. Here's the latest scoop on the newest toriccontact lens options.

Two-Week Replacement Torics

Advantages of this schedule include safety, comfort and convenience, as well as the ease in which patients wearing two-week replacement spherical lenses can be switched to toric lens correction if an astigmatic error is compromising visual performance.

Wesley Jessen's FreshLook Toric is the first toric soft lens designed for two-week replacement. It is manufactured utilizing wet mold technology from phemfilcon A, the same material used in Wesley Jessen's DuraSoft 3 lens. FreshLook Toric has a toric back surface and thin zone design with minimal prism, similar to the design of the DuraSoft 3 Optifit conventional toric lens.

Bausch & Lomb's soon-to-be-released two-week replacement SofLens66 Toric is a back surface toric design manufactured from alphafilcon A utilizing the company's Molded Form-Cast technology. The patented Lo-Torque design enhances stability of lens rotation, according to the company. In addition to prism ballasting, the lens anterior and posterior optic zone diameter is designed to decrease thickness differences across this area, providing a balanced vertical thickness profile. A 360-degree comfort chamber provides equal edge thickness around the lens circumference, minimizing potential destabilizing effects from lid interaction with the lens during a blink. The lens offers axes around the clock in 10-degree increments. I've had the opportunity to work with this lens on a population of 15 patients and have found its performance to be quite predictable.

Monthly Replacement Torics

CooperVision's Frequency 55 Toric lens joins CIBA Vision's Focus Toric in the monthly replacement lens category. The ease of remembering to replace lenses at this interval should enhance patient compliance. Frequency 55 Toric has the same design as CooperVision's quarterly replacement Preference Toric, but is made from the Frequency 55 methafilcon A material. The company plans to expand the parameters of the lens to include low plus sphere powers and a -1.75D cylinder power.

Other Options

The Multiples Toric quarterly replacement lens by Sunsoft is a front-molded, back lathed toric surface lens using prism ballasting with eccentric lenticulation. Multiples Toric offers cylinder powers up to -6.00D. Included is a -0.50DC option for the particularly sensitive patient who is disturbed by low levels of astigmatism.

Biocompatibles offers a six-month and one-year replacement cycle for its new Proclear Tailor-Made Toric. This 59 percent water content lens has the widest range of sphere powers available in a planned replacement lens. It is a lathe-cut, back surface toric design with front surface prism ballast stabilization. The Tailor-Made Toric system custom selects lens diameter (0.2mm steps) and base curve (0.1mm steps) based on the patient's spectacle prescription, keratometry readings and vertex distance. Axis orders are taken to one degree and labeled within the ANSI standard of plus or minus five degrees. Tailor-Made Toric is made from omafilcon A material, the same material used for the Proclear spherical lens.

These new lenses, in combination with available toric options and RGP lenses, give us the tools to fit virtually any healthy astigmatic patient.

Dr. Quinn is in group practice in Athens, Ohio, and has served as faculty member at The Ohio State University College of Optometry.