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OC John, T John; Ultrastructural Findings Of New "free-standing," Low-heat Dehydrated Human Amniotic Membrane . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4191.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The use of human amniotic membrane (HAM) in anterior segment surgery is slowly gaining in popularity. We studied the new, "free-standing' (without any carrier sheet), low-heat dehydrated (LHD) human amniotic membrane and compared it to other types of HAM that we previously reported. Methods: LHD HAM (n=4) was studied using light (LM), scanning (SEM), and transmission electron microscopy (TEM). Nuclear counts of toluidine blue-stained flat mounts under LM provided epithelial cell density. SEM specimens were directly processed, while other specimens were reconstituted in sterile balanced salt solution, fixed in 4% glutaraldehyde in 0.1 M sodium cacodylate buffer, and processed for LM and TEM. Results: LHD HAM samples appeared like embossed tissue paper, very light and flexible. Due to the type of mechanical processing, these specimens had a brick-like grid pattern, which on hydration becomes smooth with total loss of the grid pattern. The average thickness was 20 microns, which is similar to the fresh-frozen and freeze-dried HAM. The epithelial cell density was 117 6.4/mm2. SEM revealed the epithelial cells to be in a uniform, confluent sheet. The undersurface of the specimens revealed collagen fibrils in a random arrangement. TEM showed a single layer of epithelial cells with surface microvilli, and intercellular junctions. The stroma showed collagen fibrils and fibroblasts. Conclusion: The introduction of this new LHD HAM adds another dimension to amniotic membrane surgery. Absence of a carrier sheet allows direct ocular application of this new HAM. LHD HAM is structurally comparable to some of the types of currently available HAM for surgical use.
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