contact lens business
A Bit of Hope for the Presbyope
Another clever multifocal design increases the prospects for a good outcome and a happy patient.
By Tina Callina, COMT and Mark Packer, M.D.

Most of today's soft multifocal lenses provide simultaneous vision, with both distant and near objects presented for focus at the same time. Lens designs using this principle include:

• concentric design (a central optical area encircled by ring-shaped zones of different powers)
• aspheric design (a change in power from center to edge produced by a progressive change in curvature across the front or back surface)
• diffractive design (light rays directed to two separate foci via interference rather than refraction).

CooperVision has recently introduced a soft multifocal with an innovative new design variation that combines the principle of monovision with concentric and aspheric lens designs.

Frequency 55's "D" and "N" lenses reverse the functions of the central and peripheral zones.

The Best of Both Worlds

CooperVision's new Frequency 55 Multifocal design is a complementary inverse geometry lens system with a unique fitting approach. The "D" lens is distance-centered, and typically used for the dominant eye; the "N" lens is near-centered, for the nondominant eye. Both lenses feature a spherical central zone surrounded by an aspheric annular zone, followed by another spherical, peripheral annular zone.

Notably, the D lens and N lens have different central zone sizes:
2.3 mm and 1.7 mm respectively. (Because the pupil constricts when focusing at near, a smaller near zone is just as effective as a larger distance zone. This also allows more distance coverage in the outer rings of the N lens, improving distance vision.)

This design results in optimal vision and excellent binocular performance at all ranges. It also provides increased flexibility when fitting presbyopes with varying visual demands.

Successful Fitting

There are three keys to an excellent outcome:

Determine whether the patient's vision use is near-centered or distance-centered. For a predominantly distance-centered individual, the D lens is initially placed on the dominant eye with the N lens on the nondominant eye. For a primarily near-centered individual, the initial lens selection is reversed. The availability of three add powers (+1.50D, +2.00D and +2.50D) allows for a myriad of creative fitting strategies, so you can find the best overall visual solution for each patient.

Choose appropriate candidates. Presbyopes who are emmetropic at distance are generally less satisfied with this lens because of their normally excellent uncorrected distance acuity.

Make sure expectations are realistic. Patients may sacrifice a small amount of clarity at one or both ranges. Also, conditions that reduce contrast sensitivity may decrease near acuity slightly (although this can be remedied by the occasional use of minimally powered readers). Patients must understand that these lenses won't re- create the "perfect" vision of youth.

A Great Alternative

In our experience, patients who have been dissatisfied with other multifocal options are often quite happy with these lenses. They're definitely worth considering for the presbyopic contact lens patient.

Dr. Packer is in private practice in Eugene, Ore., and clinical assistant professor of ophthalmology at Oregon Health & Science University. Ms. Callina is a certified ophthalmic medical technologist with Drs. Fine, Hoffman & Packer in Eugene, Ore. Neither author has any financial interest in CooperVision or the Frequency 55 lens.