prescribing for presbyopia
Contact Lens Calculators
BY CRAIG W. NORMAN, FCLSA
Presbyopic contact lens manufacturers have long supplied fitting charts to help us determine the first lens. But as we become more "techno savvy" and use personal computers (PCs) and personal digital assistants
(PDAs), electronic bifocal lens calculators are becoming more popular.
I'll describe some of the multifocal calculators that are available today. Table 1 lists where you can access online these calculators. I'm sure others are available now or will be in the future.
Calculating for GPs
Blanchard Laboratories' ESSential and ESSential Xtra calculator is an excellent tool to order initial lenses in these GP designs. Simply input Ks and spectacle prescription, press the enter button and the suggested design instantly appears. For an emerging presbyope who already wears lenses, you can enter that patient's refractive findings and his present single-vision GP lens specs, and the software calculates the initial ESSential design for you. Blanchard's soft lens calculator works similarly for the ESSential Soft
Toric, Quattro and PS System designs. These calculators are available for both PCs and
X-Cel offers its X-Cel Solutions PDA Calculator for its translating bifocal lenses. This program allows you to input a description of the patient's lower lid position in addition to refractive findings to improve initial lens selection. It then provides a recommended lens design, including a suggested lens diameter and seg position. Optional choices include diameter, prism amount and prism location. It lists all available parameters and features a problem-solving section called the Rx Solver.
Calculating for Soft Lenses
Vistakon offers the Acuvue Bifocal Contact Lens Calculator for PCs. It provides easy input of patient information and spectacle prescription and doesn't require keratometric measurements because of the single base curve in this lens design. This program features problem-solving components for improving distance vision, near vision or both distance and near, plus enhanced
monovision. Its print feature provides excellent hard copy for patient charts.
CooperVision's MultiTrack is the newest multifocal calculator available. While presently available only for
PDAs, it will soon be available for PCs. Drop-down menus and arrows provide data entry without typing. Simply choose the dominant eye, select the patient's visual preference for far, intermediate or near and log in the patient demographic information. Once you enter the spectacle prescription values, the software calculates the lens parameters. A nice feature is the easily accessible help menus. You can then order the lens and save the patient's prescription data for future use. Following the initial fit, you can adjust the lens prescription to best meets the needs of the patient.
Boost Your Presbyopic Success
Try these electronic lens calculators and you may see your first fit success rates improve.
Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the RGP Lens
Contact Lens Spectrum, Issue: January 2004