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J. O. Hjortdal, A. Ivarsen, II, W. Fledelius; Long-Term Changes in Epithelial and Stromal Thickness After PRK or LASIK. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2359.
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To compare changes in epithelial and stromal thickness after LASIK or PRK over a 3-year period.
One eye in each of 45 patients with myopia ranging from -6.00 to -8.00 diopters (D) (spherical equivalent spectacle refraction) was randomized to LASIK (n = 25) or PRK (n = 20). Data were collected prospectively before, and 1 week, 1, 3, 6, 12, and 36 months after surgery. Measurements included confocal microscopy through focusing (CMTF) of the central cornea. From the CMTF intensity signal central epithelial thickness (CET) and central stromal thickness (CST) was calculated. Re-treatments were not performed during the first year, and retreated eyes were excluded from the 3-year follow-up.
CET and CST were similar in the two groups before surgery. After surgery CST increased gradually and slightly in LASIK treated eyes from 403 µm at one week to 415 µm after one year. In PRK treated eyes, CST showed a more pronounced increase from 389 µm at one week to 410 µm after one year. Following LASIK, CET changed from 46 µm pre-op to 54 µm one week after surgery, with no further changes during the first year. In PRK treated eyes CET increased from 39 µm after one week to 51 µm after one year. From one to three years after surgery CET and CST did not change significantly in either of the two groups.
The epithelium thickens after PRK and LASIK, but it takes up to one year after PRK until epithelial thickness is stable, while a stable epithelial thickness is obtained already one week after a LASIK procedure. Stromal regrowth is much more prominent after PRK compared with LASIK. Over very long time (one to three years after surgery) the thickness of the individual central corneal layers appears to be stable.
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