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R. K. Zoltoski, E. Wyles, E. A. Knighton, J. Brandt, S. Vogt, A. J. O'Brien, M. Mazurkiewicz, J. R. Kuszak; Measuring Lens Anterior Star Suture Response to an Accommodative Stimulus Across Age. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2803.
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Structural analysis of ex-vivo primate lenses suggests that the interfacing of non-uniform fiber ends at the anterior and to a lesser extent the posterior star sutures is the underlying anatomical basis for the mechanism of accommodation. Modeling of the lens has provided more information about the dynamic lens changes that occur during growth and accommodation that corroborate these observations. In this study, we report the quantitative changes in anterior star sutures during dynamic accommodation in young to presbyopic adults in-situ using the slit lamp that confirm this mechanism.
Normal myopic subjects, ranging in age from 7 to 55 (n=40), were photographed using a Haag-Streit slit-lamp (16x magnification) with particular emphasis on individual lens anterior star suture branches. Photographs of the nasal half of the lens were obtained in a dilated eye in both the dysaccommodated and accommodated states (maximal accommodative amplitude, using minus lenses). ImageJ (NIH) was used to analyze the sutures.
In all states, an anterior star-like suture pattern is visible across all ages, with increasing number of branches occurring with age. A suture branch is characterized by a dark band bracketed by a pair of broader diffuse bands. The area of the dark band (µm2) in a dysaccommodated state is similar across age (<40 years = 0.040±0.005, >40 years = 0.038±0.011). The dark band area decreases in response to a 2.5D stimulus to a similar degree in both age groups (-27.8±4.2% vs -18.9±7.0%). When further accommodation is possible, a greater decrease in the area is observed (-43.5±6.2% at 5 D and -60.5±6.7% at 10D stimulus).
The dark band of the suture branches indicates an area of minimal scatter, possibly caused by the end-to-end arrangement (non-overlapping) of fiber cells at the sutures in the dysaccommodated state. As fiber ends actively interface (overlap), there is a decrease in the area of this band. With age, lens fiber ends are still able to overlap, but there are a lesser number of shells that are capable of this overlap, resulting in a decrease in accommodative ability. Further analysis of these observations factoring in growth rate changes provide more insight into the mechanism for loss of accommodative abilities across age.
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