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R. K. Zoltoski, E. Wyles, M. Burke, M. Mazurkiewicz, J. R. Kuszak; In situ Observation of the Human Crystalline Lens Response to Dynamic Accommodation Across Age. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3778.
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Analysis of ex-vivo primate lenses suggests that an underlying basis for the mechanism of accommodation is the interfacing of fibers ends at suture branches. In an unaccommodated state, the fibers ends are arranged end to end, while during accommodation, the fibers slide over each other and overlap to create a thicker lens. We report results of in-situ slit-lamp analysis of human anterior suture appearance in the accommodated vs. the unaccommodated state that is consistent with the ex-vivo studies.
Lenses from normal myopic subjects ranging in age from 6 to 55 (n=30) were photographed using a Haag-Streit slit-lamp, with particular emphasis on individual anterior suture branches, while the subjects were either not accommodating or attempting to accommodate to a 2.5, 5, 7.5, or 10D stimulus.
When accommodation was relaxed, an anterior star-like suture pattern was visible across all ages. The number of branches increased with age, such that in younger lenses, three suture branches were the maximum seen, while in the older lenses, 4 or more sub-branches were visible. We were able to consistently observe a dark band bracketed by a pair of broader diffuse bands. When accommodation was stimulated and the subject was able to clear the image, a single more diffuse band that approximated the size of the previously described pair of diffuse bands was apparent. The central dark band became smaller as the accommodating stimulus increased. The suture patterns became much more difficult to isolate at the higher levels of accommodative stimulus in the younger subjects, as the diffuse bands of one suture branch began to blend into the diffuse bands of the next suture branch. In the older subjects, who were not able to clear the accommodative stimulus, there was little change in the appearance of the suture branches during the accommodative process.
The dark band was consistent with minimal scattering due to the end-to-end arrangement of fiber cells at the sutures in the unaccommodated state. The more diffuse bands were consistent with increased scattering due to the active overlap and interfacing of fiber ends at the sutures thereby eliminating the central dark band. Using in-situ slit-lamp analysis which was completely consistent with the ex-vivo microscopic analysis, it may be possible to objectively determine the accommodative abilities of a lens in-situ and assist in accommodative disorders diagnoses.
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