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Jose I. Velarde, Dolores Ortiz, Javier Llorca, Jose N. Fernandez Cotero; Steepening In Temporal Peripheral Corneal Topography After Lasik Surgery In Myopic Patients And Its Relation With Surgical And Ocular Parameters. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1481.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the biomechanical response of the peripheral regions of the cornea following Lasik for the correction of myopia and correlate these findings with the differences between attempted and achieved central corneal flattening values.
This retrospective study included sixty-six right eyes (28 males and 37 females) with a mean age of 32.5 ± 8.1 years that underwent Lasik with EC-5000 Nidek scanning excimer laser. A superior-nasal hinged corneal lamellar flap was made by the same surgeon using the Moria microkeratome system. The Orbscan II slit scanning software allows to obtain the numerical difference maps between preoperative and postsurgical tangential power. Data of peripheral steepening were obtained for five points placed from 150º to 210º annular zone, every 15º, with a radius between 3.5 and 4.0 mm from the corneal apex. Unintended central corneal flattening was calculated as the difference between the final central corneal power predicted by the laser algorithm and the post-surgical values.Student's t-tests and multivariate regression analysis were used to compare central and peripheral topographic outcomes, surgical parameters and preoperative values (p values lower than 0.05 were considered significant).
Three months after surgery, mean value and standard deviation of temporal steepening were 3.09 ± 2.12 diopters (-0.97 - +10.63). Regarding the unintended central corneal flattening a mean value of 0.29 ± 0.75 diopters (-2.10 - +1.60) was measured. Statistically significant correlation was found between mean temporal steepening and age (r=0.38), stromal ablation (r=0.41) and central corneal power (r=0.25); and also between unintended central corneal flattening and transition zone (r=-0.47), flap diameter (r=-0.25) and the available stroma diameter (r=0.36).
The topographical changes of the peripheral regions of the cornea, connected with its biomechanical response after the flap cut and stromal ablation in myopic LASIK, doesn't seem to have a direct relation with the differences between central corneal power, predicted by the laser algorithm, and postsurgical central corneal power values.
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