Influence of the eye refraction on the luminance-pupil diameter relationship

Purpose: Several lines of evidence have suggested that the pupil diameter is adjusted at each luminance level to provide the optimum quality of retinal image that maximizes the visual acuity. However, it is not known whether the luminance-pupil diameter (L-P) relationship is determined genetically by natural selection or adaptively based upon the retinal image quality in each individual. We conducted a study to investigate the influence of the eye refraction on the L-P relationship. Methods: Wave aberrations and L-P relationships were measured in 20 normal subjects. The wave aberration was reconstructed by the 6th order Zernike polynomial expansion, and the root-mean-square (RMS) of Zernike coefficients was used as a metric of the eye refraction. One of the subjects (Sub-TKA) underwent new corrective lenses after the initial recording, which decreased his RMS value. After re-correction, his L-P relationships were measured at 2, 4, and 8 weeks later. Results: There were considerable differences in the RMS values and the L-P relationships among the subjects. For each luminance level except under dark condition, a significant negative correlation between the RMS value and pupil diameter was found. In the Sub-TKA, his pupil enlarged gradually for about 2 weeks after re-correction. Conclusions: These two consistent results show that the L-P relationship is adaptively modified and influenced by the eye refraction.