Improving TransPRK surgery with Microscan Visum 1100 Hz device for myopia correction

Abstract

Transepithelial photorefractive keratectomy (TransPRK) with excimer laser “Microscan Visum” (1100 Hz) is a one-stage surgery which does not require changing the sequence of stages for epithelium removal and ablation of cornea stromal part. The “know-how” of Russian excimer laser manufacturers allows to significantly reduce corneal tissue overheating during TransPRK surgery. A new approach to TransPRK surgery consists in simultaneous use of Platoscan program, age nomogram and size of epithelium initial thickness.Purpose: to assess functional outcomes and changes in the corneal epithelium thickness after TransPRK surgery in patients with myopia in the period from 1 month to 1 year.Material and methods. Sixty-six eyes of 33 patients were included in the trial. Average patients’ age was 25.6 ± 6.8 (mean 17–40); 18 men and 15 women. The average spherical component was –2.57 ± 1.54 diopters (from –0.75 to –5.75). The average cylindrical component before surgery was –0.79 ± 0.71 diopters (from 0.00 to –3.5); 45 eyes with mild myopia, 21 eyes with moderate myopia. Epithelium thickness was measured with RTVue-xR Avanti device (Optovue, USA). Calculations were made using Platoscan program and age nomogram (OOO “Opto-systems”, Russia). Assessment of functional outcomes was made using generally accepted standards in refractive surgery.Results. TransPRK has shown its high efficacy, safety, predictability and accuracy in patients with myopia correction. Analysis of OCT findings of the anterior segment using epithelial maps showed that there is no complete restoration of epithelium thickness both in cornea center and in cornea periphery in 7-mm zone by the end of the first month after TransPRK surgery. In one month after TransPRK, epithelium thickness restored by 86.64 % in the center and by 87.99 % in 7-mm zone. Complete restoration of epithelium thickness in the center and in periphery was reached in 6 months. Corneal epithelium thickness in the surgical field increased by 7.9 % both in the center and in periphery in 12 months after the surgery. The ratio of epithelium initial thickness in the center and in periphery to the total cornea thickness before and after the surgery was 10–12 % for the entire study period.