Abstract
Abstract: :
Purpose: To characterize the anatomical and morphological features of human and rabbit corneal endothelial cells in the far peripheral region adjacent to Schwalbe’s line. Methods: Optisol-GS stored human corneas were obtained from the Georgia Eye Bank (ages 17-66 yrs). The peripheral corneal endothelium was evaluated on H&E sections and corneal endothelial rims (obtained from donor corneas used in keratoplasty) were stained for 7 minutes using 1% Alizarin red dye to determine far peripheral cell density. Additionally, donor human corneas were fixed for scanning and transmission electron microscopy to evaluate the peripheral anatomy. Finally, donor human corneas were stained with Bodipy phallicidin, to examine the cytoskeleton with fluorescent microscopy. For comparison, New Zealand white rabbits (10 weeks to 2 years) were obtained and the corneal endothelium was stained with Alizarin red dye to determine cell density in the central, paracentral and far peripheral regions. Results: In the human corneas, H&E staining and electron microscopy (n=9) reveal a transitional (large cells) endothelial cell zone (100-120µm across) next to Schwalbe’s line. Scanning EM montages illustrate the transitional zone. Adjacent to these cells, there is an area of markedly increased endothelial cell density (ECD). This area is approximately 100-150 µm in diameter. The corneal endothelial cells then decrease in number toward the central cornea. Far peripheral ECD from Alizarin red stained rims (n=6) also show an increased ECD when compared to central eye bank reported ECD’s. By comparison, the peripheral ECD of rabbit corneas (10 wks, 8 mos, 24 mos) show that the central ECD is greater than the far peripheral ECD which is opposite the results obtained from human corneas. Conclusions: The data from this anatomic study confirm the increased ECD in the far periphery in the human cornea. There is a definite transitional zone of larger endothelial cells adjacent to Schwalbe’s line, followed by a highly packed (greatly increased cell density) zone as one moves centrally. Peripheral ECD in the rabbit corneas are decreased compared to the central ECD’s and there is no transitional zone adjacent to the outflow channels. Supported by NEI P30EY06360, EY00933, RPB
Keywords: cornea: endothelium • anatomy • cornea: basic science