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D. M. Kleinman, D. Sobti, T. S. Rowe; A Novel Treatment Approach to Cataracts: Ray Tracing Analysis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6126.
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Cataracts are the leading cause of blindness in developing countries. Despite the success of modern cataract surgery, worldwide cataract blindness is increasing and not decreasing. Clearly, a new approach to visually disabling cataract is needed. This study was undertaken to determine the potential image quality on the retina of an eye treated with a novel interventional approach to cataracts whereby a pinhole device is placed through the opacified in situ lens.
The Liou and Brennan nominal eye model was modified by creating a pinhole aperture at the midpoint of the crystalline lens. Modulation transfer function plots were used in this model to estimate Snellen acuity for far, intermediate and near fields of vision. 16.9 million light rays were analyzed for different pinhole sizes.
With a pinhole diameter of 0.18 millimeters, potential Snellen visual acuity is in the 20/70 to 20/100 range. Larger pinhole sizes led to lower predicted Snellen acuities. Estimating the amount of light on the retina reveals a reduction from 2% of normal, as is seen in a dense cataract, to 0.2% for the 0.18 millimeter pinhole system. Larger pinholes let in more light.
This study demonstrated that a pinhole device deployed into a cataractous lens could generate clinically meaningful and much improved Snellen acuity. The image quality with the optimal pinhole size would be washed out by incident flux unless this issue is directly addressed in the novel treatment system. Further technical development is underway to create a new, easily performed technique that can play a role in eradicating global cataract blindness.
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