The Tanito microhook trabeculotomy (TMH), also called the Microhook ab interno trabeculotomy (µLOT), is a novel minimally invasive glaucoma surgery (MIGS).
The procedure incises trabecular meshwork using small hooks that are inserted through corneal side ports.
The Microhook can incise the inner wall of Schlemm’s canal without damaging its outer wall more efficiently than the regular straight knife that is used during goniotomy.
The procedure involves standard sub-tenon anesthesia using 2% lidocaine or intracameral anesthesia using 1% lidocaine. Viscoelastic material is injected into the anterior chamber (AC) through the clear corneal ports created using a 20-gauge micro-vitreoretinal (MVR) knife at the 2–3 and 9–10 o’clock positions. Using a Swan-Jacob gonioprism lens to observe the angle opposite from the corneal port, a microhook is inserted into the AC through the corneal port. The tip of the microhook is then inserted into the Schlemm’s canal and moved circumferentially to incise the inner wall of the Schlemm’s canal and trabecular meshwork over 3 clock hours. Using the same procedure, trabeculotomy is performed in the opposite angle using a microhook that is inserted through another corneal port. After the viscoelastic material is aspirated, the corneal ports are closed by corneal stromal hydration.
During µLOT surgery, 3 types of microhooks, that is, straight, angled-right, and angled-left, are used. For operability, a straight hook is used to incise the nasal angle and the right-angled and left-angled hooks are used to incise the temporal angle.
Shoji Modification:
The original TMH has demonstrated consistent IOP-lowering effects and a favorable safety profile in multiple retrospective studies. However, it may be limited by suboptimal access to the temporal angle in eyes with narrow angles, deep anterior chambers, steep cornea, or deep-set orbits. The Shoji edition was developed to address these use-case constraints, featuring a longer shaft to improve reach, a slimmer posterior profile for smoother canal access, and a wider incision arc to achieve a broader trabecular incision. These design changes were intended to improve surgical control and reproducibility while maintaining reusability.
In a study comparing the original TMH procedure and the Shoji modification reported that at 12 months, surgical success was achieved in 46.4% of the original group and 50.1% of the Shoji group; at 24 months, the rates were 32.0% and 44.2%, respectively. Kaplan-Meier estimates showed no significant difference between groups (log-rank P = 1.000). Both groups achieved reductions from baseline in mean IOP and number of glaucoma medications at all time points. Postoperative complications were infrequent and comparable between groups.
Advantages:
Advantages of µLOT include: a wider extent of trabeculotomy (two-thirds of the circumference), a simpler surgical technique, being less invasive to the ocular surface, a shorter surgical time than traditional ab externo trabeculotomy, and no requirement for expensive devices.
Because there is no bleb involved in decreasing the IOP reduction, there is less likelihood of trabeculotomy causing vision-threatening complications, for example, flat AC, bleb leaks, hypotony maculopathy, choroidal detachment, and bleb infections that can occur after trabeculectomy performed with antifibrotic agents.
REFERENCES:
- Tanito, M. (2018). Microhook ab interno trabeculotomy, a novel minimally invasive glaucoma surgery. Clinical Ophthalmology, 12, 43–48. https://doi.org/10.2147/OPTH.S152406.
- Shoji T, Nishida T, Tanito M. Original vs Shoji Edition of Tanito Microhook Trabeculotomy Combined with Cataract Surgery: Comparative Clinical Outcomes. J Glaucoma. 2026 May 1;35(5):342-347. doi: 10.1097/IJG.0000000000002667. Epub 2026 Feb 9. PMID: 41662866; PMCID: PMC13105747.
- Sasidharan, Ajita; Shah, Paraali; Thulasidas, Mithun. Short-term outcomes of Tanito microhook ab interno trabeculotomy combined with phacoemulsification in primary open-angle glaucoma – A pilot study. Indian Journal of Ophthalmology 73(Suppl 2):p S250-S253, March 2025. | DOI: 10.4103/IJO.IJO_723_24
