BY DAVID W. HANSEN, O.D., F.A.A.O.
FEB. 1996

Computers. We're all touched by them in some way. Many of our patients spend entire workdays seated at their computers, while others spend hours on the Internet in the evenings. Educational resources and games found on a computer can consume hours of a patient's visual day. Therefore, selecting the proper RGP bifocal is crucial to our presbyopic patients' vision.

DESIGN SELECTION

We now know that simultaneous or aspheric designs are more appropriate than multifocals for computer users. Translating designs usually have a "void" in the intermediate area that makes it difficult for patients to see at that critical "computer distance." Aspheric designs should be your first line of defense for patients who work at a computer more than 30 percent of their day. They enable patients to focus from far to near through the intermediate distance and provide comfortable vision without a translation "jump."

NEW OPTIONS

Within the last few months, the contact lens industry has been blessed with new designs to accentuate the intermediate distance. Tru-Form's Llevation is a translating RGP bifocal with an intermediate aspheric zone. This design allows the patient to see distance through the top portion of the lens, and near through the bottom, with a graduation of the focus in the intermediate area. Fused Kontacts developed the Tangent Streak trifocal a few years ago. This trifocal looks like an "executive" ophthalmic lens featuring the zones across the entire lateral dimension of the contact lens. Unilens Corp. introduced their Unilens Plus aspheric multifocal RGP lens that expands the parameters of the near vision and the intermediate design. This lens gives latent presbyopes and computer users a wider range of focus from far to near.

OLD STANDBYS

Conforma's VFL 3 is fit two diopters steeper than flattest K to allow greater movement through the intermediate area. This improves the flexibility of the intermediate visual demand. Permeable Technology's Lifestyle Hi-Rider lens is fit with a superior riding position and can be designed to work well with minimal head movement of the patient for more comfortable, ergonomically functional intermediate vision.

Menicon's new crescent lens in a high Dk material, the decentered DeCarle design and the Fluoroperm ST by Paragon Vision Sciences all have wide areas for near vision among translating designs.

THE BEST CHOICE

Which design is really the best? The simple answer is the one that works! As you develop a system for fitting computer users, I suggest starting with an aspheric or simultaneous lens if residual astigmatism is not a problem. Pupils of 5mm or greater under mesopic conditions can be a problem when fitting aspheric designs. The movement of translating lenses may create a vertical "jump." But flare, glare and lens movement may bring you back to aspheric lenses. I suggest reviewing your patient's visual demands, length of time spent at the computer, and environmental conditions. These three components will guide you to proper design selection. CLS

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