New Possibilities of Refractive Modeling of the Cornea by the Radiation of an Argon-fluorine Excimer Laser

Abstract

Purpose: To consider new possibilities of refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Materials and Methods: Experimental (20 pork, 90 rabbit eyes) and clinical studies on photorefractive and phototherapeutic operations with saturation of the corneal stroma with riboflavin (610 operations) were analyzed. To activate riboflavin, secondary radiation induced by exposure to ablative and subablative energy densities was used. A quick transition to energy densities below the ablation threshold without additional calibrations was carried out using a “Microscan Visum-500” excimer laser (Optosystems, Russia). An objective assessment of the refractive keratomodelling effect and visual results was carried out according to the data of complex optometric studies. Results: Experimental and clinical studies have shown the advantages of refractive keratomodeling by theradiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Isotonic 0.25% riboflavin solution did not affect the accuracy of refractive ablation and blocked the negative effect of induced secondary radiation on keratocytes and corneal nerves. This reduced the aseptic inflammatory response and the risk of developing an irreversible form of fibroplasia. Ablation with riboflavin initiated a damped crosslinking effect, which increased the photoprotective and strength properties of the thinned cornea. A refractive keratomodelling effect was found when energy densities were applied below the stromal ablation threshold. The magnitude of this refractive effect depended on the total radiation dose and the topography of the affected area. This approach made it possible to implement laser-induced refractive keratomodeling without ablation of the corneal stroma. Conclusion: Refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin opens up new possibilities in laser correction of ametropia.