Doroshenko Y. Prevention of сomplications and regression of refractive effect in laser vision correction in patients with myopia and myopic fstigmatism

The dissertation is dedicated to enhancing the effectiveness of excimer laser vision correction in patients with myopia and myopic astigmatism by analyzing factors influencing the development of complications and regression of the refractive effect and developing methods for their prevention. The dissertation is based on the results of personal observations, as well as clinical and instrumental research methods. The study presents the observation results of 100 patients (192 eyes). Gender distribution: 46 males (46%) and 54 females (54%). Age range: from 19 to 47 years (mean age 27.28 ± 1.08 years). Scientific novelty of the results obtained. This study carried out a comprehensive analysis of changes in the biomechanical properties of the cornea and tear film after excimer laser correction, which allowed us to establish key patterns and risk factors that affect the long-term stability of the refractive effect. A comprehensive analysis of biomechanical changes in the cornea after various methods of refractive surgery was improved. The latest methods for assessing the biomechanical properties of the cornea (Ocular Response Analyzer) were used, which allowed us to quantitatively determine the level of corneal rigidity after PRK, LASIK, Femto-LASIK and ReLEx SMILE. It was found that the greatest decrease in biomechanical stability is observed after Femto-LASIK and LASIK, which may increase the risk of secondary ectasia in patients with a thin cornea or high degrees of myopia. The ReLEx SMILE method has been shown to have the least impact on corneal biomechanical parameters, making it the method of choice for patients at increased risk of developing ectasia. The scientific evidence between the laser correction method and the stability of the refractive effect has been clarified. The study showed that 10% of patients operated on by the LASIK method and 7,5 % of patients after LASЕK had a regression of the refractive effect within 12 months after the operation. While Femto-LASIK and ReLEx SMILE were characterized by complete stability of the obtained refractive results, which is due to the less invasiveness of the method and minimal impact on the biomechanical properties of the cornea. It was found that the main risk factors for the regression of the refractive effect are the degree of preoperative myopia, the biomechanical characteristics of the cornea, and the presence of a history of dry eye syndrome. Further development was made in the analysis of changes in the protein-electrolyte composition of tear fluid after refractive interventions. The use of the tear fluid crystallography method made it possible to establish that in 20% of patients after Femto-LASIK, the absence of a protein zone in the crystallograms is observed, which indicates a violation of tear crystallization. It was established that in patients who underwent ReLEx SMILE, stabilization of the tear film occurred within the first 30 days after surgery, while in the Femto-LASIK group this process lasted up to 3-4 months. It was found that the most pronounced changes in the architectonics of crystals in the tear fluid were observed after methods involving the formation of a corneal flap (Femto-LASIK), which can be explained by damage to the nerve structures of the cornea and impaired tear production. It has been proven that postoperative changes in the state of the tear film directly affect the stability of the refractive effect. For the first time, an individualized approach to choosing a laser correction method depending on the biomechanical parameters of the cornea and the state of the tear film has been proposed criteria for predicting the development of postoperative dry eye syndrome depending on the tear film stability index have been proposed. Practical significance of the results obtained. The use of an algorithm for predicting the risk of complications and regression of the refractive effect after laser vision correction has been developed and proposed. This algorithm is based on a comprehensive analysis of preoperative parameters, including corneal thickness, level of preoperative myopia, tear film condition and corneal biomechanical characteristics. A postoperative monitoring system is proposed, which includes dynamic assessment of the tear film condition, corneal biomechanical parameters and level of refraction. It was found that the additional use of crystallographic analysis of tear fluid allows for a more accurate prediction of the development of dry eye syndrome and temporary prevention of this complication. The approach to choosing a refractive correction method is optimized, which allows reducing the risk of regression of the refractive effect and increasing the long-term effect of treatment.