Analysis of lateral coma changes after wearing a rigid gas-permeable contact lens and its relationship to a shift of the pupil center

Abstract

Objective To investigate the association between pupil location and lateral coma before and after wearing a rigid gas-permeable contact lens (RGPCL).Methods In this prospective case control study,corneal topography was taken from 42 bare eyes of 21 subjects before lens wear and 1 month after wearing the RGPCL and corresponding wavefront aberrations of the anterior corneal surface were calculated with a Matlab program.Pupil location and diameter were measured by corneal topography.Wavefront aberrations of the whole eye were taken with a WAVE analyzer for the same 42 eyes with and without RGPCL.And all the wavefront aberrations were calculated within a 6.0 mm area.Results The lateral shift of the pupil center was observed to be significantly temporal both for right eyes (-0.067±0.141 mm for bare eyes,and-0.103±0.129 mm after lens wear,t=2.240,P＜0.05) and left eyes (0.059±0.159 mm for bare eyes,and 0.114±0.132 mm after lens wear,t=-3.371,P＜0.01) after wearing RGPCL.And pupil diameter increased accordingly (3.69±0.61 mm for bare eyes,and 3.91±0.49 mm after lens wear,t=-2.865,P＜0.01).For bare eyes,lateral coma was significantly different from baseline when wearing RGPCL.The mean values for the baseline and lens wear were-0.104±0.075 μm,0.019±0.050 μm (right eyes,t=5.697,P＜0.01) and 0.127±0.074 μm,-0.001±0.079 μm (left eyes,t=5.113,P＜0.01) for the cornea and 0.012±0.072 μm,0.097±0.054 μm (right eyes,t=5.291,P＜0.01) and-0.038±0.071 μm,-0.099±0.051 μm (left eyes,t=4.387,P＜0.01) for the whole eye.The lateral shift of the pupil center was significantly correlated with the lateral coma of the cornea (r=-0.583,P＜0.01),whole eyes (r=-0.534,P＜0.01) and pupil diameter (r=0.501,P＜0.01).Conclusion The results suggest that the temporal shift of the pupil center could change the pattern between the cornea and whole eye from compensation to passive.And the pupil diameter may be one of the reasons for this variation. Key words: Contact lenses,rigid gas-permeable ; Lateral coma; Pupil center