Effect of intraoperative delayed time on correction accuracy in 1050 Hz excimer laser-assisted in situ keratomileusis

This study aimed to analyze and compare the effects of intraoperative delayed time (IDT) on refractive correction accuracy in femtosecond laser-assisted stromal in situ keratomileusis (FS-LASIK) using 1050 Hz excimer laser equipment. Eighty-one eyes of 81 myopic and astigmatic patients were divided into three groups according to the IDT: mild delay (IDT < 5 s, 29 eyes), moderate delay (5 s ≤ IDT < 10 s, 26 eyes), and severe delay (10 s ≤ IDT ≤ 60 s, 26 eyes) groups. Uncorrected distance visual acuity (UDVA), spherical equivalent (SE), and intraocular pressure (IOP) were measured 1 week, 1 month, and 3 months postoperatively. The static cyclotorsion and dynamic cyclotorsion components (SCC and DCC, respectively) were recorded. Central corneal thickness was measured before and 1 week after the operation. Differences in the UDVA, refractive power correction error (RPCE), and corneal ablation error (CAE) between the different groups were compared. The postoperative UDVA of the three groups was good; no significant difference as observed in the SCC and RPCE 1 week after surgery. The DCC and RPCE at 1 and 3 months postoperatively in the three groups significantly varied. For patients with an IDT less than 10 s, no significant difference was observed between the actual and theoretical ablation corneal thicknesses. However, for those with IDT longer than 10 s, the actual ablation thickness was greater than the theoretical ablation thickness. The CAE increased with the IDT lengthening, and the average actual ablation depth increased by 0.09 μm for every extra second. Education and training on preoperative ocular fixation should be emphasized. Patient delay in laser ablation due to poor cooperation may still lead to RPCE and CAE, even though the 1050 Hz excimer laser has the highest ablation speed, highest tracking speed, and seven-dimensional eye movement tracking.