Accommodation "error" and retinal image quality

Aim: A modified wavefront sensor was used to investigate the\ud effect of accommodative errors on retinal image quality.\ud Methods: Ten subjects were presented with six vergence stimuli\ud between 0.17 D and 5.00 D. For each vergence distance, subjective\ud visual acuity and ocular wavefronts were measured. Wavefronts\ud were analysed for natural pupil sizes and for a fixed threemillimetre\ud pupil diameter. Visual Strehl ratios computed in the\ud frequency domain (VSOTF) and retinal images were calculated\ud for each condition.\ud Results: Subjective visual acuity was significantly improved at\ud intermediate vergence distances (1.00 D and 2.00 D; p < 0.01),\ud and decreased significantly at 5.00 D compared with 0.17 D\ud (p < 0.05). VSOTF magnitude was associated with subjective visual\ud acuity and VSOTF peak location correlated with accommodation\ud error. Apparent accommodative errors due to spherical aberration\ud were highly correlated with accommodative lead and lag for natural\ud pupils (R2 = 0.80) and accounted for 93 per cent of the total\ud accommodative error.\ud Conclusions: The combination of higher-order aberrations and\ud accommodative errors improved retinal image quality compared\ud with accommodative errors or higher order aberrations alone.\ud The one to one stimulus/response slope should not be considered\ud as ideal in the presence of higher-order aberrations. Pupil size and\ud higher order aberrations play an important role in ASR