Abstract
Purpose: Peripheral eye shape is important in the study of eye growth during emmetropization. Peripheral retinal contour can be estimated from peripheral refractions (Dunne, 1995). We used Dunne's method to measure possible changes in retinal contour in the presence of accommodation.
Methods: Peripheral refractions were measured on 40 subjects with a COAS aberrometer (Wavefront Sciences). Refractions ranged from -12 to +2D. Measurements were taken out to +/- 50o horizontally and +/- 40o vertically in 0 D and 4D accommodative states. Accommodative demand was manipulated by viewing a target through a Badal lens system. Gaze position was controlled with partially reflective beam splitter mounted on a rotating stage. Axial length measurements were obtained using a Zeiss IOLMaster. Anterior chamber depth, lens thickness, and corneal curvature were obtained using a Pentacam.
Results: Retinal contours in high myopia were consistent with a prolate eye shape. Asphericity coefficients of retinal shape varied significantly with refraction on the horizontal meridian, but not on the vertical meridian. There was a posterior shift in calculated retinal contour with accommodation, which was minimal at the fovea and varied by as much as 0.8 mm in the far periphery. The algorithm was found to be very robust to inaccurate measures of anterior chamber depth and lens thickness.
Conclusions: Dunne's algorithm is robust to computation of retinal contour in the presence of anterior chamber inaccuracies. Accommodation apparently shifts the retinal contour; this may be associated with optical changes in the eye or an actual change in eye shape.