Retinal vessel density alteration after FS-LASIK for myopia with different axial lengths

To compare the effects of different types of negative pressure suction on the macular and optic disc retinal vessel density (VD) in myopic patients with different axial lengths (ALs) undergoing femtosecond laser-assisted excimer laser in situ keratomileusis (FS-LASIK) by optical coherence tomography angiography (OCTA).

A prospective, nonrandomized, controlled study. Participants underwent FS-LASIK surgery were divided into the short AL group (SAL, 22≤AL<26 mm) and the long AL group (LAL, 26≤AL<28 mm) according to the different ALs. Further, the two groups were divided into subgroups according to the corneal flap using VisuMax or WaveLight FS200 femtosecond laser (FS) platform. All patients underwent OCTA before the surgery and 1-day/1-week/1-month after the surgery. ANOVA statistically analyzed data with two-factor repeated measurement in SPSS.

Totally 108 participants (108 eyes, 18-35y) were divided into SAL group [22 patients (4 males and 18 females) were treated with VisuMax, and 24 (3 males and 21 females) were treated with WaveLight FS200] and LAL group [34 patients (4 males and 30 females) were treated with VisuMax, and 28 patients (6 males and 22 females) were treated with WaveLight FS200]. In the LAL group, there was no significant difference in macular superficial capillary plexuses vessel density (SCP-VD) in the fovea and perifovea region, but compared with the VisuMax subgroup, SCP-VD in the parafoveal region (t=2.647, P=0.010) and the whole area (t=2.030, P=0.047) in WaveLight FS200 subgroup decreased at one day after the operation and increased to a preoperative level at 1-week and 1-month after operation. There was no significant difference between SCP-VD in the two SAL subgroups, neither of deep capillary plexuses vessel density (DCP-VD) and optic nerve head vessel density (ONH-VD) in the SAL and LAL groups.

With the increase of AL and suction intensity, a transient decrease of SCP-VD in the macular region is observed at 1d postoperatively during FS-LASIK, and it increases to preoperative level at 1-week and 1-month postoperatively. However, the AL and suction intensity do not affect the macular DCP-VD and ONH-VD.