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J. H. Mathew, J. D. Goosey, J. P. G. Bergmanson; Stromal Lamellar Count in the Keratoconic Cornea. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3934.
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It is well known that the keratoconic (Kc) cornea becomes abnormally thin and collapses forward. The purpose of this pilot study was to establish a protocol to enable the counting of lamellae in the Kc cornea to determine whether the loss of corneal thickness is explained by a lamellar drop out.
Two surgically removed Kc corneal buttons (one due to hydrop and the other due to anterior scarring) were immediately preserved and processed for transmission electron microscopy (TEM) utilizing an established corneal protocol, ensuring minimal tissue shrinkage and distortion. A sequence of overlapping digital micrographs of the full apical cone thickness was taken at 860x microscope magnification. A seamless montage was created using PanaVue ImageAssembler 3 software and was printed (Roland FJ-52) at a final magnification of 5000x. The number of lamellae were counted using a pre-established set of criteria for identifying individual lamellae.
One of the corneas (A), with anterior limiting lamina (ALL) present, had a stromal thickness of 487um, while the other cornea (B), with ALL missing, had a stromal thickness of 212um. Cornea A had 308 total lamellae, with 64 lamellae in the anterior 100um and 62 lamellae in the posterior 100um. Cornea B had 109 total lamellae, with 41 lamellae in the anterior 100um and 59 lamellae in the posterior 100um. The anterior stroma of both corneas had an increased number of stromal cells and macrophages.
Assessment of cornea A indicated a high number of lamellae and represented an earlier phase of the disease. Cornea B, with its marked thinning and apical scarring represented a more advanced stage of the disease than Cornea A. The present study confirmed earlier observations from our laboratory that the loss of ALL is an integral feature of this disease and, for the first time, we showed that the thinning of the Kc stroma, when compared to the normal human cornea (Bergmanson, et al., Eye&CL, 31(6):281-7; 2005) is explained by the loss of collagenous lamellae. It appears that the high density of cells, especially the macrophages, was involved in the removal of tissue. The determination of exactly what is lost in the stroma of the Kc cornea is important for uncovering the cause and developing a cure for this disease.
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