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Kahook Dual Blade goniotomy may offer greater IOP reduction in patients with open-angle glaucoma

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When used as a stand-alone procedure or combined with cataract surgery, both the iStent inject (Glaukos) and Kahook Dual Blade (KDB; New World Medical) goniotomy showed a clinically significant IOP-lowering effect, according to results of the first head-to-head comparison of these MIGS technologies.

The results, which were published in the journal Clinical Ophthalmology,1 found that IOP was significantly lowered in all subgroups studied, except for a stand-alone iStent inject subgroup.

The iStent micro-implant was approved by the FDA in 2012 and the second generation iStent inject Trabecular Micro-Bypass System was FDA-approved in 2018.

According to a presentation at the 38th Congress of the European Society of Cataract and Refractive Surgeons,2 implantation with the iStent inject substantially reduced IOP in patients with open-angle glaucoma through 5 years. In this 5-year prospective study, 57 patients (57 eyes) with OAG being treated with 1 preoperative medication, underwent implantation. Efficacy outcomes included ≥ 20% IOP reduction versus baseline and IOP ≤ 18 mmHg. In more than 80% of eyes, IOP endpoints were achieved at 5 years with no medication.

The single-use goniotomy KDB device received FDA approval in 2015.

Data presented at the 2018 ASCRS Annual Meeting3 found that combining goniotomy–using the KDB–with cataract surgery appears to consistently lower IOP. In a study involving 105 eyes participants with varying levels of glaucoma severity who had previous trabeculectomy, glaucoma implant, laser peripheral iridectomy, or selective laser trabeculoplasty were included. 80% were black, 60% had diabetes, and half were taking a blood thinner. 30% had prior glaucoma laser or incision surgery. All underwent the combined procedure. Investigators measured IOP early postoperatively and at 3-month intervals for a year. Among the results:

  • Preoperatively, average IOP was 19.9 mmHg, and participants were on an average of nearly 2 medications.
  • IOP dropped to an average 16.0 mmHg at 1 month, and remained there throughout the first year.
  • 9 in every 10 eyes required no meds after the procedure.
  • No choroidal detachment, hypotony, or flat chambers were seen.
  • 2 eyes required washouts, 1 combined with an Ahmed.

Several studies have demonstrated the IOP-lowering effect of both goniotomy with KDB or iStent inject. The current study, however, is the first head-to-head comparison of the efficacy and safety profile of KDB goniotomy and iStent inject as standalone procedures or in combination with phacoemulsification cataract surgery.

In the current study, 59 patients (62 eyes) underwent goniotomy with KDB or iStent inject implantation, stand-alone or combined with cataract surgery. IOP, number of glaucoma medications, proportion of eyes achieving > 20% IOP reduction, and number of eyes with postoperative IOP < 19 mmHg at last follow-up were measured.

Patients in the KDB-alone subgroup had a mean follow-up of 20.9± 6.5 months and patients in the phaco-iStent inject subgroup had a mean follow-up of 29.5± 7.6 months.

Pre-operative IOPs in the KDB-alone, phaco-KDB, iStent inject-alone, and phaco-iStent inject subgroups were 22.2± 5.8 mmHg, 24.2± 6.8 mmHg, 20.6± 5.4 mmHg, and 20.9± 5.5 mmHg, respectively. Post-operative IOPs were 15.9± 4.3 mmHg (P = 0.004), 16.2± 6.7 mmHg ( P= 0.001), 20.9± 6.8 mmHg (P = 0.598), and 15.6± 3.4 mmHg (P = 0.003)

No major complications were recorded.

There was a mean reduction of 14.3% and 21.5% in the number of medications from baseline to last follow-up in the KDB-alone and combined surgery subgroups, respectively.

In the combined iStent inject subgroup, there was a mean reduction of 28.2% in the number of medications from baseline to last follow-up, however, there was an increase in the pre-and postoperative number of medications in the stand-alone subgroup.

The authors concluded that although both techniques appear safe and effective, “data from this study do indicate that excisional goniotomy with Kahook Dual Blade might offer a favorable IOP reduction in comparison to iStent inject implantation.”

In a Letter to the Editor regarding the study, Dr Ricardo Augusto Paletta Guedes argued that “important inconsistencies prevent definitive conclusions from the analysis.”

Dr Paletta Guedes noted that the study’s standalone iStent inject results are different than previously published studies and asked the authors to provide additional commentary and data concerning success criteria, how baseline characteristics were controlled, outlier/non-outlier results separately, amongst other things.

Dr Paletta Guedes reported being a speaker/consultant for Glaukos, Allergan, and Alcon.


  1. Arnljots TS, Economou MA. Kahook Dual Blade Goniotomy vs iStent inject: Long-Term Results in Patients with Open-Angle Glaucoma. Clin Ophthalmol. 2021 Feb 11;15:541-550. doi: 10.2147/OPTH.S284687. PMID: 33603332; PMCID: PMC7884935.
  2. Aptel F, et al. Sustained 5-year safety and IOP outcomes in open-angle glaucoma subjects treated with trabecular micro-bypass stents. Presented at: 38th Congress of the European Society of Cataract and Refractive Surgeons, October 2-4, 2020.
  3. Burk L. Combined cataract and glaucoma surgery using a single-use dual blade. Talk presented at: 2018 ASCRS-ASOA Annual Meeting; April 13-17, 2018; Washington, DC.