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A. C. Zamudio, R. Gerometta, D. Porcel, O. A. Candia; Volume Change During Accommodation in Cow and Human Lens. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2816.
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© ARVO (1962-2015); The Authors (2016-present)
To test in an in vitro cow lens and in a two-dimensional human lens model the premise that during accommodation the lens gains fluid when it gets rounder and loses fluid when it gets flatter.
Two approaches were employed: 1) Enucleated cow eyes were dissected in a way as to leave the ciliary body-zonulae-lens system intact. The ciliary body was glued to a rubber washer that could be stretched (with a custom-made device), transmitting the force to the zonulae and flattening the lens while it was submerged in either Ringer’s (RGR) or oil. Lateral photographs of the lens were taken with the lens relaxed (RLX) (i.e.: rounded) or stretched (STR) (i.e.: flattened). 2) Geometrical figures of human lenses were created in Photoshop® with data of equatorial length, anterior-posterior thickness and radii of curvature obtained from the literature. The schematics drawn were the side profiles of a) A 20 year old crystalline lens at 0 D and 10 D and b) A 45 year old lens at 0 D and 4 D of accommodation. The resulting sagittal views of cow and human lenses were analyzed by ImageJ software. From the parameters obtained, a formula derived from the horn torus was used to calculate all volumes in ml.
We obtained the following values:It can be seen that the cow lens under RGR reversibly loses volume with stretching, whereas a nonreversible change occurs under oil; until it is transferred afterward to RGR. In the human lens at both ages, a loss of volume proportional to the accommodative change is observed.
We have found in an in vitro model that simulates natural accommodation and in a geometrical model of the human lens, that a movement of fluid out and into the lens occurs during the process. This fluid movement may also take place internally between lens fibers. Thus, any impediment to this movement may impair the accommodative process.
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