Abstract
Abstract: :
Purpose: The Zernike expansion of measured wavefront aberration also includes spherical and cylindrical data of the subject's eye. The aim of the presented work was to study the effect of higher order aberrations on the wavefront refraction at different pupil sizes. Methods: Wavefront aberrations were measured in 130 untreated eyes by means of an Tscherning-type aberrometer after having dilated the pupils to a diameter of at least 6.0 mm. The wavelength used in the measuring device was 532 nm. The wavefront refractions were calculated for 3 and 6 mm pupil diameter. The change in wavefront refraction resulting from a change in pupil size from 3mm to 6 mm was correlated with the amount of higher order aberrations. Results: The correlation between the change in wavefront sphere and the amount of 4th and 6th Zernike order spherical aberration was found to highly statistical significant (p <0.001) with a correlation coefficient of R = 0.94. The change in wavefront sphere ranged from +0.4 to -0.9 D with a standard deviation of 0.3 D for all investigated eyes. A similar correlation was found for wavefront cylinder and the 4th and 6th Zernike order astigmatism (R = 0.91, p < 0.001). The change in wavefront cylinder was up to -0.8 D with a standard deviation of 0.2 D. Conclusion: Higher order optical aberrations lead to clinically relevant differences in refraction data when changing the pupil size. Thus, refraction data can only be compared at the same pupil size. In addition, such a misinterpretation of the refraction might increase the unpredictability of refractive surgery results.
Keywords: 542 refraction • 519 physiological optics • 550 refractive surgery: optical quality