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Comparative Study of Outflow Facility and Intraocular Pressure in Kahook Dual Blade and iStent Inject - A Consecutive

Thomas Sherman¹, Anindyt Nagar¹, Arij Daas¹

¹Frost Research Unit, St Thomas' Hospital, London, UK.

Clinical Ophthalmology (Auckland, N.Z.)

|August 3, 2026

Abstract

Objective:

To investigate the effects of Kahook Dual Blade (KDB) ab-interno trabeculectomy and iStent inject on tonographic outflow facility in glaucoma subjects.

Design:

Comparative non-randomised observational study.

Participants:

Adult pseudophakic patients with open angle glaucoma or ocular hypertension with sub-optimal intraocular pressure (IOP) control despite maximum tolerated medical treatment.

Methods:

All patients underwent washout of all glaucoma medications before measurement of tonographic outflow facility (TOF) and IOP. Washout TOF and IOP were repeated 3 months after the surgery with either KDB or iStent inject.

Main Outcome Measures:

Tonographic outflow facility, intraocular pressure, complication rates and number of glaucoma medications.

Results:

A total of 40 patients participated in the study, 20 eyes of 20 patients were included in each group. 20 untreated eyes acted as control eyes. All patients in the iStent group underwent drop washout. Six patients in the KDB group were unable to safely undergo washout. At the 3-months post-operative visit, the mean post washout IOP was reduced by 20% (25.0±7.1 mmHg at baseline vs 19.6±3.5 mmHg at 3 months, p=0.02) whilst TOF was doubled (0.050±0.01 µL/min/mmHg at baseline vs 0.098±0.06-µL/min/mmHg at 3 months, p=0.04) from baseline in the KDB group. The iStent group showed a nonsignificant increase in mean TOF from 0.110±0.08 µL/min/mmHg at baseline to 0.145±0.09 µL/min/mmHg at 3 months (p= 0.18) and a nonsignificant decrease in median IOP 21mmHg vs 18.7mmHg (p = 1.0), Control eyes showed no significant change in the mean IOP (20.8±5.5 mmHg at baseline vs 20.5±6.1 mmHg at 3 months, p = 0.86) and TOF (baseline 0.120±0.08-µL/min/mmHg vs 3 months 0.124±0.08 -µL/min/ mmHg, p = 0.88).

Conclusion:

We demonstrated that there is a statistically significant reduction in IOP and doubling of TOF following KDB. However, patients did not show significant changes in IOP or outflow facility after standalone iStent inject implantation.

Keywords:

MIGS aqueous dynamics glaucoma

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