Efficiency and accuracy of two computerized topography software systems for fitting rigid gas permeable contact lenses.

Abstract

Purpose: The world of computerized videokeratoscopy is continually evolving. Computerized videokeratoscope contact lens programs boast the capability to accurately design final rigid gas permeable (RGP) lens parameters and simulate contact lens fluorescein patterns. We evaluated the EyeSys System 2000 Pro-Fit software (v. 4.0) and Humphrey Atlas MasterVue Contact Lens Module (v. A6) for efficiency and accuracy in fitting RGP contact lenses on normal subjects.

Methods: Balanced manifest refractions, slit lamp examinations, and computerized topographical analysis with RGP module lens fitting were performed and compared for all eyes. Lens parameters were chosen after an optimal simulated fluorescein pattern was achieved by either accepting the initially recommended default lens or a modification. Final lens parameters were based on clinical performance.

Results: With the Humphrey Atlas software, which uses a default topographic tear clearance fitting protocol set by the manufacturer, 24/50 (48%) eyes required modifications to the default fitting parameters based on the simulated fluorescein patterns. Nine of 50 eyes (18%) required further modifications once the RGP lens was dispensed. The EyeSys Pro-Fit software, which allows a custom tear clearance fitting protocol set by the user as default, required modifications to 20/35 eyes (57.1%) from default fittings provided by the system. Six of 35 eyes (17.1%) required subsequent modifications once the RGP lens was dispensed. Comparison of the EyeSys to Humphrey modules revealed no significant difference in efficiency (P=0.51), defined as any changes required to the default parameters; however, the user made more modifications to the EyeSys module from the default setting. There was no significant difference in final success rates between EyeSys (82.9%) and Humphrey (82%) systems (P=1.00).

Conclusion: Although both topography guided contact lens modules offered accuracy in RGP fitting, a user programmed default (EyeSys) protocol did not improve efficiency in RGP lens parameter selection compared to a manufacturer programmed default module (Humphrey). The need for a knowledgeable contact lens fitter remains to guide the systems in achieving the optimal fit.