Influence of accommodation on off-axis refractive errors in myopic eyes.
BACKGROUND
This study aims to understand off-axis refraction during accommodation and to identify whether the relative hyperopia generally observed in myopic eyes changes with accommodation.


METHODS
Twenty bilateral myopes (18 to 33 years) between -0.50 D and -4.25 D (spherical equivalent) and astigmatism less than 1.25 D participated in this study. A soft contact lens was used to correct refractive error for all measurements. Non-cycloplegic autorefraction was measured at the fovea and 20 degrees, 30 degrees, and 40 degrees eccentricities in the nasal and temporal retina at distances of 2 m, 40 cm, and 30 cm.


RESULTS
Peripheral refractive error, relative to central refraction, became less hyperopic with increasing eccentricity and with increasing accommodation. Lag of accommodation increased with accommodation (p < 0.001) shifting the image-shell backward relative to the retina. In the farther periphery, there was either no change in refractive error or increased myopic shifts with accommodation. Astigmatism increased with eccentricity and significantly increased in the farther eccentricities with accommodation (p < 0.001).


CONCLUSIONS
Myopes display hyperopic shifts in the center and near peripheral field during near-viewing, while the farther periphery either remains unshifted or demonstrates a myopic shift. These results are due to the combined effect of lag of accommodation and an increased curvature of field during accommodation.
Whatham
Andrew
A
Institute for Eye Research, Sydney, NSW, Australia. andrew.whatham@gmail.com
Zimmermann
Frederik
F
Martinez
Aldo
A
Delgado
Stephanie
S
de la Jara
Percy Lazon
PL
Sankaridurg
Padmaja
P
Ho
Arthur
A
D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000628:therapy; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D009216:Myopia / Q000503:physiopathology* / Q000628:therapy; D012030:Refractive Errors / Q000503:physiopathology* / Q000628:therapy; D014792:Visual Acuity; D014794:Visual Fields / Q000502:physiology; D055815:Young Adult