Theoretical derivation and clinical validation of the resolution limit of human eye to spherical lens change: a self-controlled study

PURPOSE: The aim of this study was to deduce theoretically and verify the resolution limit of human eye to spherical lens change for more reasonable design of the trial lenses. METHODS: A total of 119 normal subjects with different myopia (not more than − 6D) were included. First, the resolution limit of discernible change in spherical power was derived based on the optical model. Then, the subjects were observed to see if they could perceive the changes in spherical power as per the resolution limit and compare the difference in the best-corrected visual acuity obtained with the resolution limit and interval of 0.25D. RESULTS: Assuming that the cone cell diameter is 3 μm and the pupil diameter of 4 mm, the theoretically resolution limit was 0.05D. When the diopter of spherical power was increased, the ratios of ability to perceive 0.05D spherical lens change were 98.3% and 96.7% in right and left eyes. When the diopter of spherical power was decreased, the ratios of ability to perceive 0.05D spherical lens change were 78.9% and 83.2% in right and left eyes. The best-corrected visual acuity obtained with the 0.05 D interval trial lens was significantly better than in the 0.25 D interval on both eyes (Right eye − 0.04 ± 0.07 vs − 0.02 ± 0.06, p < 0.001; Left eye − 0.07 ± 0.06 vs − 0.04 ± 0.06, t = 8.825, p < 0.001). CONCLUSION: The resolution limit of human eye to spherical lens change was about 0.05D and the better corrected visual acuity can be obtained by adjusting the spherical power at an interval of 0.05D. Trial registration number: ChiCTR2100047074. Date of registration: 2021/6/7.