Optimage health6/27/2023 A birth-year effect was found for those belonging to the highest quintiles of household wealth in both ELSA (β = 0.125 p < 0.001) and HRS (β = 0.170 p < 0.001). The level of education moderated the life-course effect on health in both ELSA (β = -0.082 p < 0.05) and HRS (β = -0.084 p < 0.05). Two Bayesian mixed-effects multilevel models were used to assess cohort effects on health in ELSA and HRS separately, controlling for the effect of household wealth and educational attainment. A common latent health score based on Bayesian multilevel item response theory was used. The sample comprised 55 684 participants from the first seven waves of the English Longitudinal Study of Ageing (ELSA), and the first 11 waves of the Health and Retirement Study (HRS). This study aims to analyse trends in health status in two large nationally representative samples of older adults from England and the USA. People age differently, and there is a need to disentangle whether healthy-ageing pathways can be shaped by cohort effects. Different methods of computing population averages provided upper and lower limits to the mean optical transfer function and mean point-spread function for our population of eyes.Whether worldwide increases in life expectancy are accompanied by a better health status is still a debate. Using the Marechal criterion, we conclude that correction of the 12 largest principal components, or 14 largest Zernike modes, would be required to achieve diffraction-limited performance on average for a 6-mm pupil. No evidence was found of a universal anatomical feature responsible for third-order optical aberrations. Correlation of aberrations from the left and right eyes indicated the presence of significant bilateral symmetry. The largest pupil for which an eye may be considered diffraction-limited was 1.22 mm on average. For example, the average amount of higher-order aberrations present for a 7.5-mm pupil was equivalent to the wave-front error produced by less than 1/4 diopter (D) of defocus. On average, the total wave-front variance produced by higher-order aberrations was less than the wave-front variance of residual defocus and astigmatism. To first approximation, wave-front error fell exponentially with Zernike order and increased linearly with pupil area. However, for any individual eye the aberration coefficients were rarely zero for any Zernike mode. This result indicates that a hypothetical average eye representing the central tendency of the population is nearly free of aberrations, suggesting the possible influence of an emmetropization process or evolutionary pressure. We found that the population averages of Zernike coefficients were nearly zero for all of the higher-order modes except spherical aberration. ![]() We infer from these results that subjective best focus occurs when the area of the central, aberration-free region of the pupil is maximized. The residual Zernike coefficients for defocus were not zero but varied systematically with pupil diameter and with the Zernike coefficient for spherical aberration in a way that maximizes visual acuity. Zernike expansions of the experimental wave-front aberration functions were used to determine aberration coefficients for a series of pupil diameters. ![]() Sphero-cylindrical refractive errors were corrected with ophthalmic spectacle lenses based on the results of a subjective refraction performed immediately prior to experimentation. A Shack-Hartmann aberrometer was used to measure the monochromatic aberration structure along the primary line of sight of 200 cyclopleged, normal, healthy eyes from 100 individuals.
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