Viscodilation of Schlemm canal and trabeculotomy for reducing intraocular pressure and medication use in pseudophakic eyes

Minimally invasive glaucoma surgery (MIGS) has become well established as an option for early intervention in the treatment of primary open-angle glaucoma, particularly when performed in combination with phacoemulsification cataract surgery.¹ Adoption of MIGS as a standalone procedure is also growing but lags behind use with cataract surgery.² This is likely due to a combination of reasons including product-approved indication limitations, and that in a standalone procedure, glaucoma treatment is the primary reason for surgery, whereas in a combination procedure, the MIGS component is “piggybacked” onto a cataract surgery that was already required and adds minimal additional risk. Nevertheless, there is currently a move toward “interventional glaucoma” and earlier procedural intervention.^3,4 Standalone MIGS is also an opportunity to provide a MIGS procedure to those patients who, for whatever reason, were not offered MIGS at the time of their cataract surgery. The OMNI Surgical System (Sight Sciences, Inc.) is the only MIGS FDA-cleared for both microcatheter canaloplasty and trabeculotomy in a single procedure. Three-year retrospective registry outcomes for standalone use have been reported previously.⁵ This study reports 2-year outcomes from a small, prospective multicenter study using this technology.

This was a prospective, single-arm, multicenter, study using a medication washout at study baseline, and at 12 and 24 months of follow-up. The study was institutional review board (IRB)–approved (WCG IRB, Puyallup, WA), followed the tenets of the Declaration of Helsinki, and all participants provided written informed consent before participation. The study was registered on ClinicalTrials.gov (NCT04872348) before enrollment. Eligible patients had mild-moderate glaucoma (visual field mean deviation better than −12 dB), previous uneventful cataract surgery, screening medicated intraocular pressure (IOP) <33 mm Hg using 1 to 5 topical ocular hypotensive medications, and unmedicated (after washout) diurnal IOP (mean of measurements made at 9 am, noon, and 4 pm) ≥22.5 mm Hg. All IOP measurements were Goldmann and were the mean of 2 measurements using the operator/reader method. If both of a participant's eyes qualified, the eye with the higher IOP was selected as the study eye. The surgical procedure was performed as described previously.⁶ Two-sample, 2-sided t tests were used to compare outcomes at baseline with months 12 and 24 (Microsoft Excel for Microsoft 365 MSO, v. 2506). A Bonferroni-adjusted significance level of 0.0125 was used to account for the multiple comparisons.

The study enrolled 18 participants (18 eyes) who underwent baseline medication washout. Average (SD) participant age was 75 (8.2) years, the majority were female (n = 11, 61%), and most (n = 17, 94%) identified as White race. Average mean deviation was −4.4 (5.8) dB. Diurnal IOP at baseline and follow-up timepoints is shown in Figure 1. The mean IOP reduction from the baseline of 26.1 mm Hg was −9.7 (6.3) and −10.6 (5.9) mm Hg at months 12 and 24, respectively; both statistically significant (P < .001).

Figure 1.

Mean IOP at the medicated screening visit, and at study baseline, month 12, and month 24. Study baseline and months 12 and 24 IOP were diurnal IOP and followed a washout of any ocular hypotensive medications. Error bars are ±1 SD. **Statistically significant, P < .001 vs study baseline, 2-sided, 2-sample t test.

Medication use at baseline averaged 1.8 (0.9) with all participants on at least 1 medication (range 1 to 4). Medication usage dropped to 0.9 (1.2) at month 12 and 0.5 (0.8) at month 24, both statistically significant (P < .001) (Figure 2). Two-thirds (67%, 10 of 15) of participants were medication-free at month 24.

Figure 2.

Mean ocular hypotensive medication use at the medicated screening visit, and before washout at month 12 and month 24. Error bars are ±1 SD. **Statistically significant, P < .001 vs study baseline, 2-sided, 2-sample t test.

Twelve participants reported 17 ocular adverse events, generally mild and self-resolving. Only 1 adverse event was considered to be related or possibly related to the procedure (dry eye). There were 2 secondary interventions for IOP control, an SLT at 17 months and a gel stent at 15 months.

This study shows that the OMNI procedure (canaloplasty + trabeculotomy) provides effective IOP and medication reduction when used as a standalone procedure in pseudophakic eyes. Although there are few publications reporting outcomes for this procedure in pseudophakic eyes, our results are consistent with those that have been reported. In the retrospective ROMEO study, Vold et al. reported mean 12-month IOP of approximately 15 mm Hg on approximately 1 medication (no medication washout) for standalone patients (n = 48).⁷ Follow-up of ROMEO standalone patients (n = 29) at 24 months found similar, sustained results of between 13 and 15 mm Hg on just over 1 medication.⁸ Data extracted from the Intelligent Research in Sight (IRIS) registry for a larger group of eyes (230 eyes of 196 patients) showed that the OMNI procedure resulted in reduction of mean IOP and medications from 22.1 mm Hg on 2.1 medications to 15.2 on 1.5 and 15.1 on 1.1 at months 24 and 36 with average eye level reductions of 5.6 to 7.1 mm Hg.⁵ Although the IRIS registry study population included a substantial number of eyes diagnosed with severe glaucoma and with one-third of the procedures being standalone in phakic eyes, the results are remarkably consistent with what we report here.

The most critical limitation of this study is its small size. With only 18 participants, caution should be exercised when generalizing the results more widely. Nevertheless, as stated above, the present results align well with larger retrospective study outcomes for standalone use of the OMNI procedure.^5,7,8 Another consequence of the small sample size is the possible underrepresentation of minority groups. Quigley and Vitale using a random effects model and published data from 111 papers estimated that the proportion of patients with open-angle glaucoma identifying as Black in the United States was approximately 25%; however, the proportion of Black patients undergoing standalone OMNI surgery from an IRIS registry study was 8.7%—much closer to the 6% reported herein.^5,9

Canaloplasty together with trabeculotomy as performed by OMNI provides a comprehensive treatment of the trabeculocanalicular outflow pathway that has been repeatedly shown to be safe and effective. The procedure is implant-free and is indicated for use combined with cataract surgery, or as shown here, a standalone procedure. OMNI could be a very good option for patients with glaucoma postcataract surgery.