Comparison of Standalone Tanito Microhook Trabeculotomy Between Unilateral and Bilateral Incision Groups

Background/Objectives: Trabeculotomy using the Tanito microhook (TMH) is a minimally invasive glaucoma surgery (MIGS) technique that effectively reduces intraocular pressure (IOP). The optimal incision extent for standalone TMH remains unclear. This study aimed to compare the surgical efficacy and safety of unilateral (120-degree) and bilateral (240-degree) incisions in standalone TMH for primary open-angle glaucoma or late-onset juvenile open-angle glaucoma in patients without a history of intraocular surgery. Methods: This retrospective study analyzed 81 eyes of 48 patients who underwent standalone TMH at Shimane University Hospital. Patients were categorized into unilateral (29 eyes) or bilateral (52 eyes) incision groups. The primary outcomes were IOP reduction and medication score changes over 12 months. Secondary outcomes included best-corrected visual acuity (BCVA), anterior chamber (AC) flare, corneal endothelial cell density (CECD), and postoperative complications, particularly hyphema, assessed using the Shimane University Postoperative Hyphema Scoring System (SU-RLC). Multivariate mixed-effects regression and Kaplan-Meier survival analyses were performed. Results: At 12 months, IOP reduction was comparable between the unilateral (23%) and bilateral (28%) groups (p = 0.29). The unilateral group had a significantly lower medication score at postoperative day 3 (p = 0.0057) and week 2 (p = 0.033). No significant differences were observed in BCVA, AC flare, CECD, or visual field mean deviation (MD). However, the bilateral group had significantly higher hyphema scores (p = 0.017), with more cases of layered hyphema. Conclusions: Unilateral standalone TMH achieved equivalent IOP and medication score reductions compared to bilateral incisions, with a lower risk of early postoperative hyphema. The unilateral approach may be preferable for faster visual recovery.