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Colton Heinrich, Andrew Kemp, Jessica Mathew, John Goosey, Jan Bergmanson, Texas Eye Research and Technology Center; In Keratoconus are Epithelial and Stromal Changes Correlated?. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2569.
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The purpose of this study was to quantify histopathological changes to anterior limiting lamina (ALL) and epithelial basement membrane (BM) peripheral to Fleischer’s ring in keratoconic (Kc) corneas, to determine if a correlation exists between these changes, and to search peripheral stroma for histopathological signs of prominent nerves.
Nine surgically removed Kc corneal buttons and two control corneas were preserved and processed for light and transmission electron microscopy (TEM) using an established protocol. Five digital pictures per cornea were obtained from both ALL and BM with the Tecnai G 12 twin TEM at 4200x and 16500x respectively. Two measurements were taken per micrograph using a millimeter rule and adjusted to scale. Average values were calculated and compared.
The average ALL thickness for Kc was 7.841µm (Range=5.68 - 10.22µm) and for control was 9.80µm (Range=9.70 - 9.90µm). The average BM thickness was 0.4311µm (Range=0.19 - 0.69µm) and was 0.17µm (Range=0.16 - 0.19µm) for Kc and control respectively. No correlation was found between the thickening of the BM and the thinning of the ALL (r=-0.2). Abnormal nerve fibers with thickened basement membranes were found within the Kc peripheral stromal tissue.
The thinned ALL and thickened BM supported previous reports of being characteristics in patients with Kc, not only centrally but also peripherally. However, the lack of correlation between the abnormalities of the ALL and BM provided evidence that these pathological processes are independent of each other. Stromal nerve fibers observed in the stroma were abnormal and may explain the loss of corneal sensitivity noted in Kc patients but these alterations appeared not to correlate well with their distinct prominence as seen clinically.
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