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Andrew P. Kemp, Jessica H. Mathew, John D. Goosey, Jan P. Bergmanson; Life Outside Fleischer's Ring: Pathological Changes in Peripheral Keratconic Corneas. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1103.
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To quantify the histopathological changes to the anterior limiting lamina (ALL) and the epithelial basement membrane (BM) in keratoconic (Kc) corneas peripheral to the Fleisher ring, and to determine if a correlation exists between them. A second purpose was to search for histopathological clues to prominent nerves in the Kc peripheral cornea.
Five surgically removed Kc corneal buttons (age: 16-71) and one control cornea (age: 43) were prepared for light and transmission electron microscopy (TEM) using a previously established protocol. Five pictures per cornea were taken of 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.
Kc ALL thickness ranged from 5.68μm to 10.58μm (Mean 8.22μm) and BM thickness ranged from 0.19μm to 0.69μm (Mean 0.49μm). Mean control ALL thickness was 9.7μm and BM thickness was 0.16μm. No correlation was found between thinned ALL and thickened BM (R2 0.0871). Nerve fibers with a thickened or incomplete BM and an abnormal Schwann cell and axon relationship were observed in the stroma.
The thickened BM and thinned ALL reported here supported an earlier report that these layers are involved in the progression of Kc also in the peripheral cornea. However, the lack of correlation between changes in these two layers suggested independent pathological processes. Stromal nerve fibers observed were abnormal and could explain the reduced sensitivity in Kc patients.
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