Patterns of Pre-Fracturing the Lens Nucleus Using Femto-Second Laser and Their Impact on Energy and Hydrodynamic Characteristics of Phacoemulsification

Relevance Cataract is one of the main causes of low vision and reversible blindness in the world [1]. The use of a femtosecond laser in phaco surgery provides effective and safe removal of cataracts of any density and maturity. Currently, the effect of various models of preliminary femtosecond laser fragmentation of the lens nucleus on the parameters of phacoemulsification has not been sufficiently studied. Aim To evaluate the effect of various patterns of preliminary fragmentation of the lens nucleus using a femtosecond laser on the energy and hydrodynamic parameters of phacoemulsification, as well as on the level of corneal endothelial cell loss. Material and methods Hybrid phacoemulsification was performed on 336 patients (336 eyes) with immature cataract of grade IV density according to the Buratto classification, divided into three age groups comparable with each other. Group 1 - 103 patients (103 eyes). They underwent hybrid phacoemulsification with PFF of the nucleus with a "pizza" pattern. Group 2 - 112 patients (112 eyes), fragmentation of the nucleus with a "cylinder" pattern was performed. Group 3 - 121 people (121 eyes), fragmentation of the nucleus with a "grid" pattern was performed. The VICTUS laser system was used for preliminary fragmentation of the lens nucleus. In patients with grade IV lens nucleus density, the femtosecond laser pulse power was in the range of 7700-7800 nJ [2, 3]. During the operation, the effective time of ultrasound exposure and the volume of irrigation solution required for emulsification of the lens nucleus fragments were measured. Before the operation and 3 months after, the state of the corneal endothelium was examined in all patients. Results The minimum effective ultrasound exposure time was recorded when using the grid pattern and amounted to 4.05 s (2.88; 4.74), which is significantly less compared to the cylinder pattern, where it was 4.97 s (3.78; 5.88), and the pizza pattern, equal to 6.15 s (4.52; 7.75) (p < 0.05). The volume of irrigation solution required to emulsify the lens nucleus fragments was significantly less when using the grid pattern - 41.5 ml (33.5; 49.5) compared to the cylinder patterns - 58.5 ml (51; 66), p < 0.05, and the pizza pattern - 75 ml (66; 83.5), p < 0.01. The loss of corneal endothelial cells after the use of the "grid" pattern was 8.82% (7.59; 9.87), which is significantly lower than with the "cylinder" pattern - 9.97% (8.81; 10.83), p < 0.05, and the "pizza" pattern - 11.7% (10.62; 12.97), p < 0.05. Conclusion The "grid" pattern for femtosecond laser fragmentation of the lens nucleus most effectively reduces the energy and hydrodynamic parameters of phacoemulsification, which leads to a decrease in the loss of corneal endothelial cells, and there is also the lowest ultrasound load on the intraocular structures and a minimum volume of irrigation solution for emulsification of fragments of the lens nucleus [4, 5]. Key words: "grid" pattern; cataract; femtosecond laser fragmentation; emulsification; phaco surgery; femtolase; IOL; hydrodynamics