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R. K. Zoltoski, J. R. Kuszak, M. Mazurkiewicz, M. B. Alikhan; Reverse Engineering of Human Lenses. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2018.
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We are conducting reverse engineering studies (the process of taking a system apart and then reconstructing it to understand how it works) on the human lens to better understand transparency, accommodation and cataractogenesis.
Human donor lenses (12-85 years old) collected over two decades, were dissected so as to retrieve complete suture patterns at progressive ages. Fiber shape and organization were derived from scanning electron micrographs of the lenses and this data was used to create 3D scale computer assisted drawings (CADs) of lenses at defined time points. Progressively aged growth shell CADS were then placed on a timeline and tweened to simulate lens growth throughout life (4D analysis).
In sequence, 3 branch Y, 6 branch simple star, 9 branch star, 12 branch more complex star, and 15 branch most complex star sutures are formed respectively during gestation, infancy, adolescence, adulthood and middle to old age. Each iteration begins in the inferonasal quadrant and proceeds circumferentially, a pattern consistent with the development scheme of other ocular tissue (iris, ciliary processes, etc.). More detailed analysis of individual fiber shape reveals that each iteration has key fibers that will positionally dictate the development of the next more complex iteration. In general, a fiber that defines the origin and termination of an anterior and posterior suture branch is progressively overlain by a fiber that will define the midpoint of a suture branch in the next more complex iteration. Similarly, the fiber that defines the midpoint of a suture defines the origin and termination of a suture branch in the next more complex iteration. Animated over time, this scheme produces offset suture branches are organized cumulatively into a spiral, or screw-like configuration that is conducive to the mechanism of accommodation at the lens fiber level (the interfacing of apicolateral and basolateral fiber ends at suture).
The shape and organization of fibers in lenses in concentric growth shells has been quantitatively shown to be an underlying basis of both transparency and accommodative amplitude. The results of the current study, show dynamically, how the level of complexity necessary to effect accommodation and transparency is achieved and suggests that even a minor deviation from this exact plan could result in pathology. Indeed, analysis of certain pathological lenses (from diabetics, chronic steroid users, and secondary to some invasive surgical procedures [trabeculectomy and vitrectomy]) are all characterized by abnormal suture patterns.
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