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C.-W. Kong, R. Gerometta, A. C. Zamudio, B. Wu, O. A. Candia; Rapid Fluid Flow Across Mammalian Lens Surface During Accommodation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3165.
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Our recent work demonstrated that a volume change with fluid flow across the lens surface is involved in accommodation (Gerometta et al, Am J Physiol 293, 2007). Our purpose is to determine whether this fluid flow can occur in bovine and rabbit lenses during a physiologically relevant 200 ms period representative of in vivo accommodation.
The iris-ciliary body-zonulae-lens complex (lens complex) was isolated from fresh bovine and rabbit eyes; the aqueous side of the ciliary body ring was attached with cyanoacrylate glue to a rubber washer with a central circular opening within which the lens was situated. The attached lens complex was then incubated in Ringer’s throughout the experimental procedure within a custom-built stretching device. The stretching device contained eight motors evenly mounted on a circular module. Radial stretching and relaxing actions of the motors, simulating disaccommodation and accommodation respectively, were transmitted to the lens complex via eight complementary metal hooks that clasped the pre-pierced outer edge of the rubber washer. The motors were synchronized and preprogrammed to coordinate with the shutter of a digital camera, which was aligned with its visual axis centered along the anterior-posterior axis of the lens, so that pictures of the entire anterior lens outline were captured at: 1) the naturally relaxed condition of an accommodated lens; 2) after the lens stretching was accomplished, increasing its mean equatorial diameter (ED); 3) 200 ms after the stretching force was instantaneously released; and 4) 5 s after the stretching force was released.
Upon the imposition of an average increase in ED of ≈ 3 % (corresponding to a volume decrease of ≈ 6 % in bovine) with respect to the relaxed condition, a photograph was taken; photographs taken 200 ms after the release of the stretching force showed that in the cow (n = 9), 90 % of the increased ED reverted to its relaxed control value, while in the rabbit (n = 9), 98 % of the increased ED returned to its control value. Total recoveries to the control ED values were seen in both species 5 s after the stretching force was released.
Changes in lens volume observed with an in vitro model for accommodation occur within a physiologically relevant time frame, implying a rapid movement of fluid to and from the lens during accommodation.
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