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O. Fass; Quantification of Diameter Changes in the Post Capsulorhexis Lens Capsule in Response to the Range of Forces the Ciliary Muscle Exerts Upon it . Invest. Ophthalmol. Vis. Sci. 2003;44(13):274.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Many of the new forms of accommodative intraocular lenses have hinges that are placed inside the remaining capsular bag after cataract extraction. The change in shape of this capsular bag in response to accommodation puts pressure on the hinges and dictates the position of the lens. As the lens moves along the visual axis the image it forms also moves and accommodation is facilitated. Although much is known about the nature of the natural lens' responses to accommodation, almost nothing is known about the empty capsular bag's response to accommodative forces. The purpose of this experiment is to apply the known forces of accommodation (as established by RF Fischer et al. in the Journal of physiology 1977;270(1):51-74) and to observe the effect they have on the empty capsular bag. Methods: Capsulorhexis and extraction of the nucleus and cortex of the lens was performed on two porcine eyes leaving the posterior capsule intact. Three sutures were placed through the ciliary muscle at 120 degrees apart from each other. The specimen was placed in a tank of water and the sutures were stretched over a series of low friction pulleys. At the end of the sutures a series of adjustable weights were attached to simulate the known range of accommodative force. Two methods were used to gauge the capsular bag change in diameter. The first capsule was measured with ultrasound and the second was measured with a digital camera with 10x zoom function. In the latter, the lens was photographed next to an object of known diameter (a dime). The change in shape of the capsule was calculated by a ratio comparison under high magnification. Results: The force was recorded in Newtons x 10-5 and plotted against millimeters of capsule diameter. The equations for ultrasound and digital camera were respectively: Y=.0012x + 10.94 / Y = .0006x + 7.7. Conclusions: A linear relationship between accommodative force and capsular bag stretch has been found and quantified. This equation shows a diameter change of 1mm from baseline in response to maximal accommodative forces, a value that may prove useful in the dynamics of hinged accommodative lenses.
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