prescribing for presbyopia

It's Time to Switch to an RGP Bifocal

BY DAVID W. HANSEN, OD
SEPTEMBER 1999

How many times are you fooled by a patient who requires multiple visits to satisfy their presbyopic needs? You look at their records and see that they are an emerging presbyope who has previously worn soft, single-vision contact lenses, but who became frustrated with the "four B syndrome" (Bifocal patient needing Blepharoplasty surgery with Bad dry eyes and Big pupils). Each one of these individual characteristics is enough to frighten even the most experienced specialty lens clinician. But which one do you tackle first? Do you keep the patient in soft lenses? Do you switch them to monovision? Do you prescribe new designer frames and progressive lenses? What should the patient expect? What should you expect?

Recently, I learned that the aging process can be cruel and unfair and that the principles of good contact lens fitting are still a pre-eminent factor in satisfying a patient's needs.

Previously, I discussed the critical physical measurements needed for successful fitting, including refraction and cornea and lid measurements. So why did I dismiss these principles when listening to our patient express her frustration with presbyopia? I fell into the "soft lens trap," where many clinicians believe that soft lenses are the most comfortable modality and that "those patients would never get accustomed to RGP contact lenses."

A Real Life Example

Patient's Refraction:

OD -3.00 + 0.50 x 65 20/20

OS -3.00 +0.50 x 115 20/20

Central Corneal Findings:

OD 43.37/44.12 @ 66

OS 44.00/44.87 @ 100

The physical measurements of the patient's eyes and eyelids were considered normal except for a slight superior lid ptosis. Since she was new to the office, her previous lid structures were unknown. A Zone Quick Test, a tear break-up time (TBUT) analysis and corneal topography all confirmed a slight dryness of the eyes and she complained of poor near vision with her soft single-vision contact lenses. This myopic patient with pupils in excess of 4.5mm had me considering soft bifocals.

However, many of the new soft bifocal lenses, which have "zones" due to the immobility of the hydrogel material, produce flare and glare and poor distance acuity when the pupils are excessively large. Her large pupils made most soft bifocal designs unacceptable. I became increasingly aware that the best lens for her was an RGP design. Although I have enthusiastically prescribed RGP bifocal contact lenses for years, I thought to myself, "How will she accept this? Will she be able to tolerate them?" As I prepared her for her next diagnostic appointment, I knew that this was the modality that would offer her the greatest visual acuity and comfort and the best chance for long-lasting success.

Switching for Success

I truly believe that I can transfer my optimism about RGP lenses to my patients. When I entered the exam room a week later, after the patient had worn her RGP aspheric multifocals for almost a 1/2 hour, her opening comments were, "These aren't bad. In fact, they're very comfortable, and they're better than I thought they would be." I completed the diagnostic process by modifying the refraction, adjusting the fit of the contact lens and observing the movement. Soft lens patients can be converted to RGPs and are usually enthusiastic and successful about the change. Why then are we so afraid to switch materials?

My credo is to provide good binocular vision with comfortable lenses. Switching a soft lens patient to RGPs can make a patient commit to your practice for years. Are YOU willing to switch? CLS

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