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Ann Barker-Griffith, Jerrold Abraham, Hengsheng Fang, Mark Breazzano; Comparative Anatomy of Trabeculum and Smooth Zone (Schwalbe's Line) Widths of Various Primate and non-Primate Eyes by Scanning Electron Microscopy (SEM). Invest. Ophthalmol. Vis. Sci. 2013;54(15):3036.
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Animal eyes are often used in glaucoma research, but the anatomy of the irido-corneal angle has not been well defined across all species. A remaining question is which species best represents the human eye structurally. We studied the width of the smooth zone and trabecular meshwork in several commonly used animals and human, by SEM, to test the hypothesis of whether an animal model has trabeculum and smooth zone widths similar to the human eye.
Corneal-scleral rings were extracted from various formalin-fixed animal eyes, dehydrated in ethanol, and critical point dried. Scanning electron microscopy generated images of the corneal endothelial smooth zone, if present, and trabeculum from which each quadrant was measured and width calculated. The animals studied to date include: monkey (2), dog (2), pig (9), cow (6), rabbit (8), and human (26).
Preliminary studies showed absence of smooth zone in the dogs, monkeys, rabbits, and pigs studied. Furthermore, these species showed uniform width of the trabecular meshwork in all quadrants, whereas the bovine eyes showed varying trabecular widths and presence of a smooth zone (248 ± 53 µm). We have previously shown that human eyes have a wider smooth zone (103 ± 8 µm) in the superior quadrant.
The bovine eye possesses a smooth zone (Schwalbe's line) and variable quadrant width of trabeculum as in human eyes. Therefore, the cow eye may serve as a more appropriate candidate for in vivo studies. The monkey, dog, rabbit and pig eyes have dissimilar trabeculum and smooth zone anatomy from the human eye; raising questions on the suitability of these species in modeling certain human eye diseases.
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