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Marco Lombardo, Giuseppe Lombardo, Pietro Ducoli, Sebastiano Serrao; Eight Years Changes In Corneal Topography Following Advanced Surface Ablation For Myopia And Myopic Astigmatism. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5785.
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To analyze the anterior corneal topography changes during an eight years follow-up after photorefractive keratectomy (PRK) with smoothing for the correction of myopia and myopic astigmatism.
Sixty-six eyes (thirty-three patients) underwent PRK with smoothing using the Technolas 217C excimer laser platform (Bausch & Lomb, Dornach, Germany). Patients were subdivided into three groups according to the preoperative refraction: the low myopia, the high myopia and astigmatism group. Corneal topographic maps were obtained with a Placido disc topographer. The preoperative and postoperative topographical data were imported into custom software which computed the average corneal maps and average difference maps for each study group in order to quantify the corneal response to surface ablation during follow-up. Changes of surface topography inside and outside the ablation zone, which was 6.00 mm in diameter for all eyes, were further investigated.
The central region of anterior corneal topography was almost stable in all study groups, with changes less than 0.25 diopters (D) between 1- and 8-years postoperatively. A different response, in relation to the amount of refractive correction, has been measured in the peripheral cornea during follow-up: a higher flattening (P<0.05) of the peripheral region has been assessed in the high-myopia group (-0.85 D) in comparison with the low-myopia group (-0.42 D) between 1- and 8-years postoperatively. The corneal periphery steepened (+2.22 D; P<0.05) following the correction of myopic astigmatism during follow-up.
The anterior corneal topography proved to change configuration even long-term after surface ablation. Changes were mostly confined to the non ablated peripheral portion of the cornea, 6.00 to 8.00 mm from the corneal apex. PRK for the correction of myopia up to -9.00 D was shown not to influence the mechanical stability of the corneal tissue during an eight years postoperative period.
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