Observation on effects of femtosecond laser assisted laser in situ keratomileusis for ultra-high myopia

Objective To evaluate the effect and safety of femtosecond laser assisted LASIK (FS-LASIK) in the treatment of ultra-high myopia , and to evaluate the efficacy and safety of different times after the operation. Methods The clinical data of 106 patients (211 eyes) with ultra-high myopia who were followed up for more than 1 year, was conducted between January 2013 and January 2016 in Hospital of Shanxi Province. Among them, there were 50 males (100 eyes) and 56 females (111 eyes). Age from17 to 43, average (24.09±5.32) years old. Routine ophthalmologic examinations were performed before and after surgery at 1 month, 3 months, 6 months and 1 year. Routine visual acuity was performed before surgery, including uncorrected visual acuity (UCVA) and corrected visual acuity (BCVA). The visual acuity records were indicated by the logMAR. The range of refraction, including balloon, column, and equivalent spherical lenses were examined. Exclusion of anterior segment disease, using non-contact tonometer, using binocular indirect ophthalmoscope after mydriasis fundus examination, using phoropter, using corneal topography exam and corneal shape by AB ultrasound scanning and biological measurement of corneal thickness and axial length by slit lamp microscope examination. The cornea was cut by femtosecond laser system and excimer laser. UCVA, BCVA, safety index, effective index and diopter were examined at different time after operation. Validity index=postoperative UCVA/preoperative BCVA, safety index=postoperative BCVA/preoperative BCVA. The visual acuity, safety index, effective index and diopter before and after the operation were indicated by mean ± standard deviation(±s). The overall difference between the indexes at different time points before and after the operation was compared by single factor repeated measures analysis of variance, and the multiple comparisons in the group were checked by LSD-t test. The comparison of refraction regression at different time points after operation was performed by chi square test. Results There were significant differences in UCVA at different time points before and after operation (Ftime=2767.01, P 0.05). There were significant differences in refractive regression at different time points (χ2=13.69, P<0.05). Conclusions FS-LASIK are effective in the treatment of ultra-high myopia. UCVA at each time point after 1 year was better than preoperative BCVA. With the increase of time, refractive regurgitation rate increased, after 1 year to reach 7.58%. Key words: Femtosecond laser; Laser in situ keratomileusis; Ultra-high myopia