Impact of scleral tunnel length on the position of IOLs in flanged intrascleral haptic fixation

Purpose: To investigate the effect of scleral tunnel length on the effective lens position and tilt of the intraocular lens (IOL) in flanged intrascleral haptic fixation (ISHF) using anterior segment optical coherence tomography (AS-OCT). Setting: Tertiary institution. Design: Retrospective case-control study. Methods: This study included 55 and 42 eyes that underwent ISHF with 1.0- and 2.0-mm scleral tunnels, respectively. Twenty-three eyes that underwent sutured fixation were used as a control. The anterior chamber depth (ACD), scleral tunnel length, incident angle of haptic, and tilting of optic were analyzed using AS-OCT. Results: The mean postoperative ACD, vertical tilt angle, and spherical equivalent of the 1.0-mm were 5.27 ± 0.39 mm, 6.04 ± 4.87°, and 0.38 ± 1.03 D, respectively. The ACD and vertical tilt angle of the 1.0-mm were larger than those of the others (p<0.001 and p<0.05, respectively), and the postoperative spherical equivalent was more hyperopic (p<0.05). The 2.0-mm exhibited a lower frequency of tilting greater than 7°. The inter-eye difference in ACD between in-the-bag fixation and ISHF of the1.0-mm tunnel was significantly greater than that in the 2.0-mm tunnel (p<0.05). The 1.0 mm tunnel had a significantly larger incident angle and a longer tunnel length (p<0.001, respectively) and showed a greater difference in the tunnel length on both sides (p<0.05). Conclusion: A shorter tunnel yielded a more unstable IOL position, greater variation in angle and tunnel length, and longer ACD during ISHF. An exact 2.0-mm tunnel must be created on both sides to achieve a stable and predictable IOL position.