PubMed · 8064624
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A Ghiaroni, L Daher. 1994. The triangular suture.. https://doi.org/10.1016/s0886-3350(13)80605-0
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PURPOSE: To define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK), assess changes in patterns, associations with clinical outcomes, and the accuracy of videokeratography in predicting results, and define quantitatively the optical zone contour. METHODS: Computer-assisted videokeratography data obtained from 181 patients after PRK was analyzed. Topography patterns at two time points were characterized, and associations with clinical outcomes were tested. Power change predicted by topography was compared with refractive change, and cross-sectional power contours were analyzed. RESULTS: Seven topography patterns were defined. At 1 year, 58.6% of corneas showed a homogeneous topography, 17.7% showed a toric-with-axis configuration, 2.8% showed a toric-against-axis configuration, 13.8% showed an irregularly irregular topography, 2.8% showed a keyhole/semicircular pattern, and 4.4% showed focal topographic variants. No central island patterns were found. Of the maps, 41% changed over time. Uncorrected vision, predictability, and patient satisfaction were best in the homogeneous group. Astigmatism increased in the irregular and toric-against-axis groups and decreased in the toric-with-axis group. There was no relation of topography pattern to best-corrected vision or subjective glare/halo. Cross-sectional power profiles showed a homogeneous power change for the central 3 mm with a diminution in correction toward the periphery. The topography unit tended to overestimate refractive change for corrections of 5 diopters or less and underestimate the change for corrections greater than 5 diopters. CONCLUSIONS: Topography patterns after PRK are identifiable, time dependent, and may affect clinical outcomes. Understanding the actual corneal optical contour resulting from PRK may aid in improving both laser techniques and optical results in the future.
This article describes a diamond knife designed for safer, more precise extension of pre-existing refractive keratotomy incisions. The knife has a blade with a sharp vertical cutting edge whose progress is limited by a dull safety stop. The stop prevents extension of a wound by more than 500 microns at one time, minimizing the possibility of overextending the keratotomy incision into the optical zone. Because it requires no footplate, the knife improves visibility, allowing for more precise surgery.