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Thomas D Raymond, James Copland, Steve Farrer, Wei Xiong, Daniel R Neal; Effect of the induction of cyclopegia on corneal topography. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1537.
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This retrospective study investigates the effect of cycloplegia on keratometry and corneal topography. Cycloplegic drugs are commonly applied to enable measurement of wavefront over large pupils for LASIK planning. In a previous study Zhou et al1 found no significant effects to corneal aberrations using a Placido disk topographer. This study revisits this topic with particular attention to keratometry and keratometric angle using a spot based topographer.
Wavefront refraction, wavefront aberration, keratometry, corneal topography and pupil diameter measurements were taken on 76 eyes of 44 subjects with virgin eyes. The measurements were acquired with the iDesign combined instrument before and after the application of 1 drop of cyclopentolate 1% at least 30 minutes prior to induce cycloplegia. In contrast to the previous studies which used Placido based corneal topography the instrument used here measures corneal topography with the iDesign spot based corneal topographer with coverage to the corneal vertex. Keratometry magnitudes, K1 and K2(steep) and steep meridian axis (K2 Angle) were analyzed using a matched pairs analysis as were the wavefront aberrations through fourth order.
The mean pupil diameter increased from 6.31 ± 0.85(1σ) mm to 7.66 ± 0.62(1σ) upon application of the cycloplegic drug; the average matched pairs difference was +1.57 ± 0.07 mm. The matched pairs analysis for K2-K1 and K2 Axis are shown in Figure 1. The astigmatism magnitude mean difference was -0.036D ± 0.016(1σ) D which was statistically significant with a P value of 0.01. The axis mean difference was -0.68 ± 1.98 (1σ) degrees which was not statistically significant (P value 0.36).
The use of cycloplegic drugs has a statistically significant effect on corneal astigmatism, but the effect is not clinically significant. The astigmatism axis was found to be unchanged. We conclude that the use of cycloplegic drugs did not significantly alter the corneal astigmatism. 1. F. Zhou, L.N. Thibos and D.T. Miller, The effect of cycloplegic drugs on corneal and whole-eye aberrations of the human eye, Invest Ophthalmol Vis Sci 2004;45: E-Abstract 2833; © 2004 ARVO. All authors are employees of Abbott Medical Optics.
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