Contribution of Shape and Gradient Refractive Index to the Spherical Aberration of Isolated Human Lenses

Abstract

Three-dimensional sOCT and LRT allowed reconstruction of lens geometry and GRIN in isolated lenses. The constancy of the GRIN axial power exponent, and the opposite slopes of surface and nucleus indices with age, explain the minor variations of the average index. Both geometrical changes and increase in the GRIN meridional power exponent contribute to the age-dependent shift of negative SA.

OCT 3-D surface topography of isolated human crystalline lenses

“…Dubbelman et al showed that the asphericity of human lenses in vivo tends to increase with age for both anterior and posterior surface [22]. These results are in agreement with the report by Birkenfeld et al on ex vivo lenses [9].…”

“…Methods for securing human tissue were in compliance with the Declaration of Helsinki. The handling and experimental procedures, described in detail in a prior publication [9], have been approved by the institutional Review Boards of BST and Consejo Superior de Investigaciones Científicas (CSIC). The post-mortem time varied between 1 and 3 days at the time of the experiment.…”

“…To produce a complete image of the crystalline lens, two images were captured in each position, one with the OCT focused in the first surface visible (anterior in the anterior-up image and posterior in the posterior-up image), and another with the OCT focused in the second surface and showing the image of the cuvette holding the lens and the preservation media. The procedure was described in more detail elsewhere [9].…”

“…Data ex vivo and in vivo differ primarily because the isolated lens appears in its maximally accommodated state, and therefore the young lens shows large steepening ex vivo. Ex vivo, the anterior and posterior lens surface radii of curvature tend to increase with age (at least up to past the presbyopia onset) [9,21], while in vivo, both surfaces tend to steepen with age [22].…”

“…In addition, the crystalline lens shows a gradient refractive index (GRIN) distribution, which also changes with age [4][5][6][7][8]. Recent work has shown that in human [9], as well as monkey [10] and porcine lenses [4], both the lens shape and the GRIN play a role in the negative spherical aberration of the lens.…”