Troubleshooting Aspheric Designs: How Do I Manage Poor Visual Acuity and Inferior Decentration?
Aspheric multifocals and combination annular-aspheric designs are very easy to fit — typically empirically — using the assistance of the laboratory consultant as well as the design fitting nomogram.
Front-surface aspheric designs are often fit “On K,” and back-surface aspheric designs are often fit approximately 1D or more (depending upon back-surface eccentricity) “steeper than K.” Good centration and limited movement are important.
If the lens is dropping inferiorly, selecting a steeper base curve radius (often by 0.50D) is recommended. Alternatively, a larger lens diameter can be used as well.
Poor Visual Acuity
As these are center-distance designs, poor vision at distance often can be managed by achieving good centration. The exception would be if the patient has large pupils (≤ 6mm), in which case an aspheric design would likely not be successful.
Poor vision at near often can be managed by selecting a back-surface lens design that allows for adding more add power on the front surface. In addition, most laboratories can design the multifocal to incorporate a higher add power.
GP Lens Institute
- Building Your Practice with GP Bifocals and Multifocals
- GP Case Grand Rounds Troubleshooting Guide
- Contact Lens Clinical Pocket Guide
- GP Lens Management Guide
- Bennett E.S., Henry V.A. Contemporary Multifocal Contact Lens Primer.
- Rakow P. Refitting Soft Multifocal Patients into GPs.
- Davis R., Eiden S.B. A Rational Approach to Fitting Multifocal Lenses.
- Benoit D. Empirical Fitting of GP Multifocal Lenses.
- Quinn T., Davis R. Evolution in Fitting a Hybrid Multifocal Lens.
GP Lens Institute Advisory Committee members: Bruce Anderson OD, Marlane Brown OD, Carmen Castellano OD, Walter Choate OD, S. Barry Eiden OD, John Laurent OD, PhD, Derek Louie, OD, MS, Joe Shovlin OD, Frank Weinstock MD, Bruce Williams OD.