Diferentes concentraciones de mitomicina C en la prevención del haze en la queratectomía fotorrefractiva / Different concentrations of mitomycin C for haze prevention in photorefractive keratectomy

Objetivo: Evaluar la utilidad de dos concentraciones de mitomicina C para la prevención del haze en la queratectomía fotorrefractiva. Métodos: Se realizó un estudio experimental aleatorizado en 26 ojos de 17 pacientes con defectos miópicos. Los pacientes fueron asignados a dos grupos según las dosis de mitomicina C (0,02 por ciento grupo 1 y 0,002 por ciento grupo 2). La variable de respuesta principal fue la presencia de haze. Se buscó correlación entre la magnitud del haze con grado de ametropía tratada, profundidad de ablación, microscopia endotelial y resultados visuales y refractivos. Resultados: A los 6 meses la mayoría de los pacientes del grupo 1 no presentó haze (ocho ojos / 57 por ciento), y del grupo 2 mantuvieron haze 0,5 (6 ojos / 50 por ciento). En la ametropía severa el haze en el grupo 2 fue mayor que en el grupo 1 durante todo el posoperatorio, y se observó la mayor diferencia al sexto mes con 0,5 ± 0,4 vs. 1,5 ± 0,32. En ablaciones > 75 micras el grupo dos terminó con más haze que el uno, con 0,5 ± 0,44 vs. 1,75 ± 0,76. La agudeza visual sin corrección se vio más afectada en el grupo 2. No hubo daño endotelial en ningún grupo. Conclusión: La presencia de haze predomina en los casos tratados con dosis 0,002 por ciento de mitomicina C, comparada con la dosis 0,02 por ciento, aunque en este caso ambos grupos mantuvieron un resultado visual y refractivo adecuado y baja toxicidad endotelial.

Objective: Evaluate the usefulness of two concentrations of mitomycin C for haze prevention in photorefractive keratectomy. Methods: An experimental randomized study was conducted of 26 eyes of 17 patients with myopic defects. The patients were divided into two groups according to their mitomycin C doses (Group 1: 0.02 percent and Group 2: 0.002 percent). The main response variable was the presence of haze. Verification was performed of the correlation between haze magnitude and the degree of the ametropia treated, ablation depth, endothelial microscopy, and visual and refractive results. Results: At six months most patients in Group 1 did not have any haze (eight eyes / 57 percent), whereas 0.5 (6 eyes / 50 percent) in Group 2 still had haze. In severe ametropia, haze was larger in Group 2 than in Group 1 throughout the postoperative period, the greatest difference being observed in the sixth month with 0.5 ± 0.4 vs 1.5 ± 0.32. In ablations > 75 microns, Group 2 ended with more haze than Group 1, with 0.5 ± 0.44 vs 1.75 ± 0.76. Uncorrected visual acuity was more affected in Group 2. No endothelial damage occurred in either group. Conclusion: The presence of haze prevails in cases treated with 0.002 percent doses of mitomycin C, as compared with 0.02 percent doses, though in this case both groups maintained an appropriate visual and refractive result and low endothelial toxicity(AU)

Comparison of 5468 retreatments after laser in situ keratomileusis by lifting the flap or performing photorefractive keratectomy on the flap. / Comparación de 5.468 retratamientos tras láser in situ queratomileusis levantando el lentículo o mediante queratectomía fotorrefractiva sobre el lentículo.

PURPOSE: To assess visual outcomes of retreatment after laser in situ keratomileusis (LASIK) by lifting the flap or performing photorefractive keratectomy (PRK) on the flap, as well as to establish whether there was an increased risk of epithelial ingrowth (EIG) when LASIK and lifting of the flap are separated by a long time interval and to determine the incidence of corneal haze after PRK. METHODS: Retrospective study of 4077 patients (5468 eyes) who underwent LASIK and subsequent retreatment were reviewed in order to study their visual results and identify cases of EIG and corneal haze. RESULTS: Enhancements included 5196 eyes from 3876 patients that were retreated by lifting the flap, and 272 eyes from 201 patients that were retreated by PRK on the flap. No statistically significant differences were found between the retreatments in terms of predictability, efficacy, and safety. A total of 704 cases of EIG were found after lifting the flap, for which surgical cleansing was necessary in 70. Surgical cleansing decreased the efficacy index when compared with patients with EIG who did not need cleansing (P=.01). Differences in terms of safety and predictability were not statistically significant. The incidence of corneal haze after ablation of the surface of the previous flap was 14.34%, although none of these cases were clinically relevant. CONCLUSIONS: Visual outcomes were similar between patients who were retreated by lifting the flap and those who underwent PRK. The incidence of EIG when the flap was lifted was 13.55%. The incidence of EIG increases with the time elapsed between the primary procedure and retreatment.