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D.H. Geroski, D.G. Dawson, G.P. Holley, H.E. Grossniklaus, H.F. Edelhauser; Correlation of confocal microscopy to the histology and ultrastructure of human LASIK corneas . Invest. Ophthalmol. Vis. Sci. 2004;45(13):195.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To correlate ex vivo confocal microscopy to histology and ultrastructure in human corneas after LASIK surgery. Methods: Postmortem corneas (n=6) from 4 patients with a prior history of LASIK surgery (19–30 months postop) were received from U.S. eye banks. The corneas which had been stored in Optisol GS for 3–5 days, were mounted in a chamber and the endothelium perfused with BSS Plus (37o C, 15 mm Hg) for 1 hour. Confocal microscopy with the Nidek Confoscan 3 was performed in the center of each cornea. The corneas were then processed for toluidine blue stained light microscopy and transmission electron microscopy. Normal Optisol GS stored (34 hrs to 5 days) corneas were examined in a similar manner as controls. Results: Confocal microscopy was found to produce optical sections of 30 µm in thickness which were able to clearly identify the LASIK flap interface region in all corneas. Flap thicknesses measured by confocal microscopy were found to correlate closely to the flap thickness measurements obtained by light microscopy examination. The interface region showed a normal density of quiescent keratocytes with scattered bright microdots measuring 2.0 µm in diameter and particles that measured 10–15 µm in diameter. Light microscopy of this same region showed a 2–4 µm thick PAS positive lamellar scar that was present in all corneas as well as foci of microscopic epithelial ingrowth. Transmission electron microscopy (TEM) showed that the central lamellar scar measured 1.3 µm–5.0 µm in thickness which predominantly consisted of electron dense granular material with small amounts of normal diameter collagen fibrils that were randomly directed and wide–spaced. The electron dense material appears to be produced by quiescent keratocytes that are present around and occasionally in the wound. Sections of the lamellar scar region occasionally contained intracellular vacuoles measuring 0.5 to 2.3 µm in diameter present in the keratocytic cell processes and isolated necrotic epithelial ingrowth cells measuring 13 um in diameter.Conclusions: The central region of human LASIK corneas shows histologic and ultrastructural characteristics of a hypocellular lamellar scar with a normal density of surrounding keratocytes. Confocal microscopy is able to identify the scar mainly by the appearance of bright reflective microdots and particles in the optical sections containing the interface region. Clinicopathologic correlation suggests that the microdots and particles represent intracellular vacuoles in interconnecting processes of keratocytes and implanted necrotic epithelial ingrowth cells, respectively
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