COMPARISON OF EMPIRICAL VERSUS DIAGNOSTIC FITTING OF DISPOSABLE SOFT TORIC LENSES

Jacqueline Tan

Abstract

PURPOSE. To compare the empirical and diagnostic fitting methods in the selection of soft toric contact lens cylinder axis. METHOD. In a cross-over design dispensing study, 19 subjects were fitted bilaterally with four disposable prism-ballast lenses, and one dynamic stabilisation lens design. Lens orientation was measured using 10x magnification, a thin slit beam and a rotating protractor of a biomicroscope. Accuracy of empirical fitting cylinder axis selection was determined by comparing the percentage of lenses orienting within +/- 100 from the target position (zero mislocation) after one week of lens wear. Diagnostic fitting selection accuracy was determined by comparing the percentage of lenses at one week orienting within +/- 00 from lens orientation measured at Dispensing (20 minute settling). Fisher''s Exact Test was used to compare empirical versus diagnostic fitting data.

RESULTS. When fitted empirically, the percentage of cylinder axes orienting within +/- 100 from target for the five lens types ranged from 44-78%. The diagnostic fitting method selected a cylinder axis location within +/- 100 of expected orientation ranging from 50-84% for the five lens types. Diagnostic fitting significantly improved the cylinder axis selection over empirical fitting for only one prism ballast design (58% to 83% of lenses within +/-100 of target, p = 0.04). The dynamic stabilisation design had the lowest percentage of lenses within +/- 100 for empirical fitting, and this was not significantly improved by diagnostic fitting (44% vs 50%, p = 0.81). The prism ballast design that had the highest percentage of lenses within +/- 100 when fitted empirically was not significantly improved by applying a diagnostic fitting method (78% vs 84%, p = 0.75).

CONCLUSIONS. This study concluded orientation performance varied substantially between lens types. The best method for determining soft toric cylinder axis was design dependent. For four of the five designs tested, diagnostic fitting did not improve cylinder axis selection over empirical fitting.

Details

Year: 2001

Program Number: Poster 16

Author Affiliation: CRC for Eye Research & Technology, Uni of NSW

Co-Authors: Arthur Back, Thomas Naduvilath

Co-Author Affiliation: CRC for Eye Research & Technology, Uni of NSW, CRC for Eye Research & Technology, Uni of NSW

Room: Exhibit Hall C