prescribing for presbyopia

Multifocal Selection That's Above Par

BY DAVID W. HANSEN, OD

In the game of golf, selecting the appropriate club is critical for a winning game. Of the 14 golf clubs permitted in the bag, more than one may be useful in a particular situation. The same is true when confronted with a presbyopic contact lens dilemma -- you need to carefully select the most beneficial option for the patient's needs. Counsel presbyopes about the multifocal options, explaining soft and RGP advantages and disadvantages. Can we switch a successful hydrogel patient to RGPs? Absolutely, and I do it all the time. Are RGPs the only successful modality? No! There's a wide variety of soft multifocals now available. So remember, no one club is right for every shot.

Soft Multifocal Considerations

Age, refraction, corneal topography (and central K reading), pupil size and patient visual demands will usually help you select the appropriate soft or RGP lens.

Age -- If the patient is an emerging presbyope (early 40s) with intermediate demands and no severe astigmatism, consider a soft multifocal lens. After about age 47, soft multifocals are less likely to be successful, and you'll want to explore the RGP options.

Refraction -- Although we now have soft multifocals for most prescriptions, including astigmats, there are limitations to consider. Is the patient a severe astigmat? Is intermediate acuity needed for computer work for more than 30 percent of the day? Is overall visual acuity critical for occupational demands?

Small to moderate astigmatism can be resolved with the latest soft lens bifocal technology by Westcon and Ocu-Ease. Intermediate needs can be met with any number of simultaneous image lenses such as Unilens, Allvue, SoftSite and Simulvue (Unilens); Sunsoft's MultiFocal and Additions; Wesley Jessen's Hydrocurve II bifocal; 4-Vue and Xtra (The Lifestyle Co.); Specialty Ultravision's Specialty Progressive; PolyVue (Ideal), Esstech PS and PSD Bifocals (Blanchard); Bausch & Lomb's Occasions; Abcon's Abcon D and N; the Acuvue Bifocal; and others. Soft multifocals produce good acuity, but with a different type of sharpness. Education will help create realistic expectations. Some patients demand the acuity of their eyeglasses or of a translating RGP, while some patients will trade acuity for the perceived comfort of a soft lens. I say "perceived" comfort because RGPs can be very comfortable but usually require excellent edge contours and some adaptation.

Corneal topography (and central K) -- As in single-vision designs, corneal toricity can be masked in multifocals. If there is significantly less refractive astigmatism than the corneal astigmatic topography, you can use a soft multifocal lens. The position of the overall contact lens may be affected by the apex location on the cornea. Soft multifocals with larger diameters will usually provide optimum centration and utilization of the different zones of the lens.

Pupil size -- In my view, pupil size is more critical in soft lens designs because they have predetermined zone sizes, but RGPs can be manufactured with various parameters. Also, many of the hydrophilic lenses have center near designs which can interfere with pupil size. So, pupil measurements with various light intensities are critical.

Visual Demands -- Remember, the patient's computer usage is probably the most useful factor to know when making a multifocal selection. Choose a lens that provides the maximum intermediate acuity. Center near lenses are an excellent choice for computer users because they usually don't have distance acuity demands. Even modified monovision can assist near and distance changes in focus. CLS

Dr. Hansen, a diplomate and fellow of the American Academy of Optometry, is in private practice in Des Moines, Iowa.