Peripheral Autorefraction Repeatability and Peripheral Defocus of Myopic Eyes with Spherical Soft Contact Lenses

Purpose: Peripheral retinal defocus has been implicated in the progression of myopia. The purpose of this thesis was to assess the repeatability of peripheral autorefraction, and to determine the effect of commercially-available soft contact lenses on peripheral defocus of myopic eyes.

Methods: Twenty-five young adults with spherical equivalent refractions between –0.50 D and –6.00 D were enrolled. Cycloplegic autorefraction of the right eye was measured centrally and ±20°, ±30°, and ±40° from the line of sight along the nasal and temporal retina using a modified Grand Seiko WAM-5500 autorefractor. Experiment 1) The between-visit repeatability of peripheral autorefraction measurements using the Grand Seiko was determined in normal eyes. Measurements were made at two visits separated by 1 to 15 days. Five autorefraction measurements at each location were converted to vector space and averaged. Between-visit repeatability was evaluated by plotting the difference versus the mean of the measurements at the two visits (bias) and by calculating the 95% limits of agreement (LoA). Experiment 2) Four commercially-available spherical soft contact lenses (Biofinity, Acuvue2, PureVision2, and Air Optix Night & Day Aqua) were used to correct each subject. Five measurements per location were converted to power vectors and averaged. Spherical equivalent defocus (M) was used to calculate relative peripheral defocus (RPD) while wearing each contact lens and relative peripheral refraction (RPR) with no lens on the eye by taking the difference between each peripheral measurement and the central measurement. Analyses were conducted using repeated-measures analyses of variance (RM-ANOVA) and Benjamini-Hochberg adjusted post-hoc t-tests, when indicated.

Results: The mean age (±SD) and central spherical equivalent refractive error were 24.0 ± 1.3 years and -3.45 ± 1.42 D, respectively. Experiment 1) There was no significant between-visit bias for any refractive component evaluated (M, J0, J45, and RPR) at any location measured (all p > 0.05). The 95% LoA (repeatability) for defocus (M) was ±0.21 D centrally. RPR repeatability decreased with increasing eccentricity to ±0.67 and ±0.82 D at 40 degrees nasally and temporally on the retina, respectively. Experiment 2) PureVision2 did not change relative peripheral defocus (p=0.33). Acuvue2, Biofinity, and Air Optix Night & Day Aqua caused a significant myopic shift on the temporal retina (all p<0.02).

Conclusion: With knowledge of the repeatability of on- and off-axis cycloplegic autorefraction with the Grand Seiko, changes in peripheral measurements can be properly interpreted in longitudinal studies. Overall, these results show that the design of spherical soft contact lenses can influence the peripheral defocus profile experienced by a myopic eye. Though spectacles have been reported to increase peripheral hyperopia, several contact lenses tested reduced peripheral hyperopia. Longitudinal studies are required to more fully understand the impact of peripheral defocus on myopia progression and eye shape.