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1 Farmacología & Oftalmología, Universidad Nacional Del Nordeste (UNNE), Corrientes, Corrientes, Argentina
2 Ophthalmology, Mount Sinai School of Medicine, New York, New York, United States
3 Farmacología, Universidad Nacional Del Nordeste (UNNE), Corrientes, Corrientes, Argentina
* To whom correspondence should be addressed. E-mail: oscar.candia{at}mssm.edu.
During accommodation, mammalian lenses change shape from a rounder configuration (near focusing) to a flatter one (distance focusing). Thus, the lens must have the capacity to change its volume, capsular surface area, or both. Because lens topology is similar to a torus, we developed an approach that allows volume determination from the lens cross-sectional area (CSA). The CSA was obtained from photographs taken perpendicular to the lenticular anterior-posterior (A-P) axis and computed with software. We calculated the volume of isolated bovine lenses in conditions simulating accommodation by forcing shape changes with a custom-built stretching device in which the ciliary body-zonulae-lens complex (CB-Z-L) was placed. Two measurements were taken (CSA and center of mass) to calculate volume. Mechanically stretching the CB-Z-L increased the equatorial length and decreased the A-P length, CSA, and lens volume. The control parameters were restored when the lenses were stretched and relaxed in an aqueous physiological solution, but not when submerged in oil, a condition with which fluid leaves the lens and does not re-enter. This suggests that changes in lens CSA previously observed in human could have resulted from fluid movement out of the lens. Thus, accommodation may not only involve changes in capsular surface but also in volume. Further, we calculated theoretical volume changes during accommodation in models of human lenses using published structural parameters. In conclusion, we suggest that impediments to fluid flow between the aquaporin-rich lens fibers and the lens surface could contribute to the ageing-related loss of accommodative power.
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