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Komzak et al. Mini-invasive Surg 2021;5:13 I http://dx.doi.org/10.20517/2574-1225.2020.103 Page 7 of 14

Figure 2. Hydrus microstent (Ivantis inc, Irvine, CA, USA). (A) diagram of the Hydrus microbypass stent with the anterior chamber
forward. (B) is an image of the posterior chamber. Image copyright of Ivantis, Inc.

Hydrus was also investigated as a head-to-head comparison with 2 first-generation iStent (both performed
following uncomplicated cataract surgery) in the COMPARE trial, a 152-patient randomised clinical trial
[8]
by Ahmed et al. It was concluded in this study that Hydrus reduced IOP at 12 months by 1.7 ± 4.0 mmHg
compared with a reduction of 1.0 ± 4.0 mmHg in the 2-iStent group, a difference of 0.7 mmHg (95%CI:
-2.0-0.7). Medication reduction was also greater as Hydrus achieved a reduction of 1.6 ± 1.2 medications vs.
1.0 ± 1.2 in the 2-iStent group, a difference in 0.6 medications (95%CI: 0.9-0.2). Interestingly, Hydrus was
able to achieve a ≥ 20% IOP improvement in 39.7% of patients compared with only 13.3% in the 2-iStent
group and was able to achieve 30.1% in the ≤ 18 mmHg category compared with only 9.3% in the 2-iStent
[8]
group .
Hydrus: Safety profile
Adverse events were roughly comparable between both of the groups in the COMPARE trial in terms of
BCVA loss, IOP spikes, new cataracts and device obstruction. 2 patients in the Hydrus (n = 74) and 1 in the
2-iStent (n = 76) experienced a BCVA loss of > 2 lines at 12 months, and IOP spikes of > 10 mmHg were
seen in 3 patients in the Hydrus group and 4 patients in the 2-iStent group. New cataracts were seen in 2
patients in the Hydrus group and in 1 patient in the 2-iStent group and device obstruction due to any cause
was seen in 9 of the Hydrus and 10 of the 2-iStent patients.

Safety of the Hydrus microstent was generally reflective of the safety of other trabecular microbypass
devices. There was also no need for any incisional glaucoma surgery in the Hydrus group compared with
in the 2-iStent group, where 2 patients (of 76 in that group) required a secondary trabeculectomy and 1
[8]
patient required a cataract surgery .
Ab-interno canaloplasty: Mechanism of action and efficacy
Ab-interno canaloplasty (ABiC) is a procedure where a microcatheter such as the iTrack device (Ellex
Medical Lasers Pty Ltd, Adelaide, Australia) is used to perform 360˚ viscodilation of Schlemm’s canal,