Optimising RGP lens fitting in normal eyes using 3D topographic data

Abstract

Purpose: To analyse, retrospectively, the effect of fitting characteristics on comfort of wear and the role that 3D topographic data can play in attaining an optimal lens fit with rigid gas permeable (RGP) contact lenses in normal eyes. Methods: Included were 60 normal myopic eyes (1.00–5.00 D) with astigmatism limited to 2.00 D. Lenses were ordered empirically, based on traditional fitting rules. Results: The initial fit based on traditional computation was accepted in 40% of the eyes. To achieve an acceptable fit, 15% of the eyes needed an adaptation of the back optic zone radius, in 28% switching from a multicurve to an aspheric lens design was indicated and in 17% a non-rotational symmetric lens design was favoured. The reason for changing the lens parameters could in 88% be attributed to mid-peripheral differences between corneal shape as found with 3D corneal topography. Average comfort of wear improved statistically significantly ( χ 2, P<0.05) from 5.2 initially to 7.7 after 3 months in the group with optimal lens fits, while comfort slightly decreased (not significant) in the group with sub-optimal fits. Switching to a non-rotational symmetric lens design, when indicated, improved comfort significantly ( χ 2, P<0.05) from 5.0 to 7.3. Conclusion: In normal eyes, the measurement of corneal shape, especially in the mid-peripheral regions, is of importance to optimise RGP lens fit. Optimised lens fits increases comfort of wear.