Abstract
Purpose: :
Understanding peripheral optical errors and their impact on vision is important for various applications, e.g. for research on myopia development and optical correction of patients with central visual field loss. We have previously shown that resolution of peripheral low contrast objects is affected by defocus, with a loss of 0.15-0.20 logMAR/D in the 20° nasal visual field. Besides refractive errors, peripheral image quality is also degraded by higher order aberrations, primarily coma. In this study, we investigated whether correction of higher order aberrations with adaptive optics (AO) improved resolution beyond what was achieved with best refractive correction. Furthermore, we investigated the benefit of running the adaptive optics correction continuously throughout the experiment.
Methods: :
A laboratory AO system, using the Mirao™ 52D deformable mirror and the Haso™ wavefront sensor, was constructed for correcting peripheral aberrations. Through careful design of the system, it was possible to run the closed loop correction continuously for a long time, as opposed to running a closed loop in the beginning of the experiment and then freezing the mirror (frozen closed loop correction). The peripheral low contrast grating resolution acuity in the 20° nasal visual field of the right eye was evaluated for 12 subjects (age 33 ± 11 years) using three types of correction: optimal refractive correction of sphere and cylinder, frozen closed loop AO correction and continuous closed loop AO correction. Acuity at each type of correction was assessed three times per subject and polychromatic light was used.
Results: :
Running AO in continuous closed loop improved acuity compared to refractive correction for some subjects (maximal benefit 0.15 logMar, mean benefit 0.04 ± 0.06 logMAR), despite the fact that chromatic aberrations were left uncorrected. Visual benefit of aberration correction was highly correlated with initial amount of higher order aberrations (p=0.001, r=0.81). Frozen closed loop AO did not improve acuity compared to refractive correction (mean benefit 0.00 ± 0.04 logMAR).
Conclusions: :
Correction of peripheral higher order aberrations can improve low contrast resolution for some subjects, provided refractive errors are corrected and the system runs in continuous closed loop.
Keywords: aberrations • visual fields • visual acuity