Peripheral aberration measurements: elliptical pupil transformation and variations in horizontal coma across the visual field

Abstract

Background:  The aim was to determine the critical eccentricity at which two methods of elaborating peripheral wavefront measurements are significantly different and to characterise horizontal coma in healthy young adults.

Methods:  Peripheral aberrations were determined for 20 observers for central and eight peripheral gaze positions up to 20° using an IRX‐3 aberrometer. In one subject, additional measurements up to 40° were obtained. Two definitions of stretching coefficients were compared. The raw empirical data were compared with theoretical modelling.

Results:  For both 3.5-mm and 6.0-mm pupils, no significant differences were observed between recalculated and non‐recalculated elliptical pupils for both methods (p > 0.05) up to 20° eccentricity. For eccentricities greater than 20° and up to 40°, significant differences between circular and elliptical pupils at some eccentricities were apparent, which corresponded to theoretical models. Wide individual variations in horizontal coma across the peripheral field were observed.

Conclusions:  The data suggest that for eyes with average levels of aberrations, the elliptical transformation is of no practical importance for eccentricities up to 20°. In some cases the slope of horizontal coma was reversed compared with previous findings in normal eyes.

Key words:

• aberrometry
• elliptical pupil transformation
• horizontal coma
• myopia
• peripheral aberrations

ACKNOWLEDGEMENT

The authors thank Linda Lundström for providing the Matlab code for recalculating the Zernike aberrations and are grateful to David Atchison for his help with theoretical modelling and comments on a draft of the article.