Toric Soft Lenses for Planned Replacement

BY THOMAS G. QUINN, O.D., M.S.
SEPT. 1996

Now our astigmatic patients can enjoy all the benefits of frequent replacement -- improved safety, more consistent comfort and enhanced visual performance -- with toric soft lenses. Patients appreciate the less rigorous care regimen and the security of having a new lens readily available in case they lose or damage a lens. Parents like knowing their teen-ager lens wearers have this safety margin built into their contact lens system.

WHAT IS AVAILABLE?

Table 1 lists the parameters of the three currently available systems, all of which are prism ballasted.

TABLE 1: FREQUENT REPLACEMENT TORIC SOFT LENSES
LENS TYPE*	MATERIAL	TORIC SURFACE	BASE CURVE	OAD	SPHERE POWER	CYLINDER POWER	AXES	OZ
Gold Medalist Toric (Bausch & Lomb) 4 pk/ DW	57% H20	front	8.3, 8.6	14.0	+4.00 to -6.00	-0.75, -1.25, -1.75	90 & 180 ± 200 100 steps	8.0
Focus Toric (CIBA) 6 pk/ DW or EW	55% H20	back	8.9, 9.2	14.5	+4.00 to -6.00	-1.00, -1.75	Around clock 100 steps	7.5
Preference Toric (Cooper) 4 pk/ DW	43% H20	back	8.4, 8.7	14.4	plano to -6.00	-0.75, -1.25, -1.75, -2.25	Around clock 50 steps	8.6

Although manufacturers are expanding parameters, limitations do exist, particularly in cylinder power, so be sure the power you need is available before extolling the benefits of frequent replacement lenses to your patients.

Bausch & Lomb's Gold Medalist Toric is designed similarly to its Optima Toric. The material characteristics are different though, resulting in different on-eye performance. The smaller size of the Gold Medalist Toric can benefit patients with small apertures who have difficulty applying lenses. B&L provides spherical prism ballasted Gold Medalist trial lenses for easy calculation of desired lens power following a sphere-cylinder overrefraction. From this, you may order individual sphero-cylinder diagnostic lenses for dispensing and response assessment. If you must change parameters, discard these individual lenses and order new trial lenses.

Gold Medalist Toric lenses are supplied in packs of four. Dispense a single pack per eye for quarterly replacement, or three packs per eye for monthly replacement.

The Focus Toric lens by CIBA Vision is made of the same material as the Focus spherical lens and the Spectrum lens. This material is somewhat slippery, so be sure patients can remove the lens before leaving the office. Instilling a drop of lubricant in the eye prior to removal often facilitates this process. Thin orientation lines inscribed on the Focus Toric lens are sometimes difficult to find while viewing the lens on the eye with a slit lamp. Create a horizontal slit lamp beam to help locate these markings.

CIBA Vision has Focus Toric fitting sets and you may order individual lenses to assist with fitting. If you must change parameters, discard the initial diagnostic lenses and order new ones.

Focus Toric is offered in packs of six for monthly replacement. It is approved for daily or extended wear. My experience has shown all soft toric lenses are better worn on a daily wear basis. This minimizes the potential adverse effects from the diminished oxygen transmissibility associated with prism ballasted lenses.

The Preference Toric lens by CooperVision offers the widest variety of astigmatic power options. It is now available in an 8.4 base curve in addition to the original 8.7 base curve design. Its 43 percent water content material has good deposit resistance and is easy to handle. A diagnostic set of eight is available.

The Preference Toric is marketed for quarterly replacement as a box of three lenses with a fourth lens shrink-wrapped to the box. This fourth lens is dispensed as the initial lens. If modifications are needed, return this lens to the supplier along with the unopened box of three lenses within 100 days. If the initial lens is successful, simply dispense the three lenses. CLS