RGP Multifocals For Dry Eye Patients

BY DAVID W. HANSEN, O.D.
AUG. 1997

Dry eyes is the number one visual complaint of contact lens patients, and RGP multifocal contact lenses compound the problem due to their thickness and the translation movements needed to produce optimum visual acuity. Before prescribing these specialty designs, it's important to perform a thorough diagnostic evaluation that includes tests for dry eye.

PATIENT HISTORY

Be sure to take a careful medical history at each yearly examination to assess changes in the patient's general health and environment. Patients in the presbyopic age group are often on medical treatment programs, especially systemic medications, that can exacerbate dry eye. Some problematic systemic medications include: antihistamines, which dry out the tear layer; hormones, which can alter visual acuity; contraceptives, which can induce corneal edema; and dermatological products such as Accutane, which decrease lacrimal production causing the drying effect.

Work and leisure environments that may alter tear production or cause dry eyes include low or high humidity, wind, dust and poor air quality. Prolonged computer usage can also have a drying effect due to inappropriate or reduced blinking.

TEAR VOLUME AND QUALITY

I suggest measuring tear volume and lacrimal quality before attempting a multifocal contact lens fitting. The Zone Quick test, distributed by Menicon, provides a good assessment of tear volume and is easily administered. The standard tear breakup time test (TBUT) is also essential for determining tear quality and for assessing a clinical comparison of the two eyes. Reduced tear volume may indicate the need for punctal occlusion to augment the reservoir of tears bathing the contact lens. Rapid tear breakup should prompt further evaluation of the meibomian and accessory glands for lid disease.

CONTACT LENS MATERIALS AND CARE PRODUCTS

The contact lens care products must be in synergy with the lacrimal system or dry eyes may result. Research has shown that high Dk materials are beneficial for corneal health, but clinically we know that material wettability is required for patient comfort. So for thinner, aspheric simultaneous RGP designs, I recommend using a lower Dk material with better wettability. For translating lenses, which are traditionally thicker, I recommend higher Dk materials to avoid the ocular health problems associated with corneal hypoxia.

LENS MOVEMENT AND SURFACE QUALITY

Aspheric or simultaneous contact lenses require critical centration over the pupillary axis and usually have less movement, so they may seal off, inhibiting the tear exchange behind the contact lens. You can evaluate this with fluorescein. If a translating lens moves too much, the mechanical movement of the lens physically hitting the glands may produce mucus and other meibomian secretions that can coat the lens, thereby reducing oxygen transmissibility, comfort and acuity. Inspect the surface quality of the contact lens at least annually. Lenses that are scratched, or those coated with cosmetics, aerosol sprays or other artifacts that produce barriers for tear exchange, must be replaced.

SUCCESS THROUGH OCCLUSION

I've found that punctal occlusion is often a beneficial addition to RGP contact lens wear in the aging presbyope. Diagnostic punctal occlusion with collagen plugs, followed by silicone implants, may greatly enhance your chances for success. CLS

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