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Peripheral Refraction And Aberratios: The Influence Of Accommodation


Purpose: : It has been suggested that peripheral optics and accommodation may have relevance in myopia development. However a complete description of peripheral retinal image quality as a function of accommodation has not been obtained yet. In this context, we measured peripheral wavefront aberrations for different accommodation stimuli.

Methods: : We used an open-view scanning peripheral wave-front sensor based on the Hartmann-Shack (HS) principle (Jaeken et al, Opt Exp 2011). The sensor operates in infrared light and measures the central 80o of visual angle along a horizontal meridian in 1.8 seconds. The path length between the eye and the first element of the HS sensor is constant across angles. A complete series of wavefront aberrations is obtained every 1o. A high contrast Maltese cross was used as accommodation stimulus for target vergences of -0.25D, -1D, -2D, -3D and -4D. Both eyes of 4 near-emmetropes and 4 moderate myopes (wearing habitual contact lens corrections) were measured. While accommodation was binocular, target and HS system alignment were maintained on the test eye. High angular resolution data of mean spherical equivalent (M), astigmatism (A), spherical aberration (SA) and horizontal (CH) and vertical (CV) coma were retrieved from the HS images analysed for a 4-mm pupil. Relative changes in peripheral refraction with respect to the central accommodation response were also calculated. We analysed each variable using multiple regression (MR) with main effects of target vergence, refractive group and up to 3rd-order trend in angle and their interactions.

Results: : The foveal accommodation response followed typical behaviour, exhibiting accommodative lag that increased with target vergence. All variables showed significant (p<<0.01 all variables) mirror symmetry between eyes. Notable statistically significant (p<0.05) effects from MR included: M, A, CV and SA changed with target vergence while CH did not. All variables showed tilt (1st-order) asymmetry except M. All variables exhibited curvature (2nd-order) except M and asymmetry of curvature (3rd-order) except CV. (e.g. on average, A increased by more than 1 D at 30o visual angle for the -4D target.) Interaction effects involving target vergence showed that tilt changed with accommodation for all variables except M and CV while curvature changed with accommodation for all variables except CV.

Conclusions: : Small, but statistically distinguishable changes in peripheral optics due to accommodation have been measured. Even with the small sample size, we found differences between refractive groups in asymmetry and curvature. These observations may be relevant to refractive error development and worthy of further investigations.

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