Subfractional composition of tear fluid after RLEX Smile femtosecond refractive surgery. Comparative study
Purpose. Investigating the characteristics of the ocular surface and corneal tissue reaction after ReLEx Smile surgery by analyzing the subfractional composition of tear fluid using laser correlation spectroscopy and compared with other types of refractive corneal surgery. Materials and methods. The prospective research included 65 patients (129 eyes) with myopia (mean 4,85 ± 1,77D): 16 patients (32 eyes) after PRK surgery, 16 patients (32 eyes) after Trans PRK surgery, these operations were performed on the excimer laser Schwind Amaris (SCHWIND eye-tech-solutions), and 33 patients (65 eyes) after ReLEx Smile surgery, performed on the femto laser VISUMAX (CZM). The eye washout containing tear film was taken before, one day and within a week after surgery: on day of epithelization (day 4th) in PRK and Trans PRK groups and on 7th day for patients of the ReLex Smile group. Afterwards, the laser correlation spectroscopy (LCS) analysis of washout was performed and data were compared, taking into account that degenerative processes are increasing low weight molecules proportions and cellular metabolism changes are increasing the proportion of moderate weight molecules. Results. On the1<sup>st</sup> day after surgery, LCS in all groups shown a spectrum shift in middle-size fractions (100-600 nm), with a statistically significant difference (p <0.05). We discovered the differences between PRK and Trans PRK in middle range particles (91-223 nm) - 17,2%, 5,2% accordingly, and in high weight range (600-2000 nm) for PRK, Trans PRK group and ReLex Smile - 3.1%, 6.0% and 1.8% accordingly. After 1 week, only in the ReLex Smile group, the overall picture of the spectrum is became almost the same as it was before surgery. In the other groups, we observed an increase of middle size particles. Conclusions. We consider a less tissue damage in ReLex SMILE group according to a shorter and less significant changes in tear film in this group. It associated with less traumatization of the cornea by a femtosecond laser. Also, a smaller size and faster sealing of the corneal incision could explain it. We assume that ReLex Smile has a less traumatic effect on the cornea than other investigated types of corneal laser refractive surgery.