Modern laser technologies for additional correction of ametropia after previous correction of myopia and myopic astigmatism

The aim of the study: To compare the results of different methods of additional correction of ametropia after previously performed laser correction of myopia and myopic astigmatism. Research methodology: A retrospective randomized study was conducted. The study included 144 patients (230 eyes) who were undergone additional correction of ametropia at different times after previous laser correction of myopia and myopic astigmatism (LASIK, FemtoLASIK, CLEAR). The average age of the patients was (34.2 ± 6.58) years. The refractions values before correction of ametropia were as follows: spherical component (-1.1 ± 0.9) diopters; cylindrical component (-0.5 ± 0.5) diopters, and spheroequivalent (-1.4 ± 0.89) diopters. The pachymetry values were (472.9 ± 39.5) micrometers. The average time between primary and repeated surgery was (5.85 ± 6.0) years. Five options were used for re-intervention: lifting the corneal flap formed during the primary surgery; forming a new corneal flap thinner than the primary flap (flap in flap); forming a new edge of the primary corneal flap using a femtosecond laser and lifting it (side-cut-only); transepithelial photorefractive keratectomy (trans-PRK); and forming the corneal flap edge mechanically using a dissecting knife after CLEAR-technique. The results of the research: Uncorrected distance visual acuity (UDVA) on the first day after additional correction was (1.07 ± 0.2); spherical component was (-0.0 ± 0.38) diopters; cylindrical component was (-0.25 ± 0.5) diopters, sphere equivalent was (-0.14 ± 0.5) diopters. Keratometry indicators were K min (38.6 ± 1.8) diopters; K max was (39.2 ± 1.9) diopters. Root mean square (RMS) wave-front indicators in the 5 mm zone were (0.51 ± 0.2). Contrast sensitivity values were (43.3 ± 14.79) at 4 mm, (44.86 ± 14.5) at 5 mm and (44.1 ± 14.1) at 6 mm. Conclusion: Post-laser correction of ametropia can be achieved in various ways, depending on the presence or absence of a corneal flap, its thickness, and the residual corneal stroma.