Abstract
ObjectiveTo assess anterior segment optical coherence tomography angiography (AS-OCTA) imaging of the episcleral vessels before and after trabecular bypass minimally invasive glaucoma surgery (MIGS).DesignA prospective, clinical, single-centre, single-arm pilot feasibility study conducted at National University Hospital, Singapore.SubjectsPatients with primary glaucomatous optic neuropathy undergoing Hydrus Microstent (Ivantis Inc., Irvine, CA, USA) implantation, who require at least one intra-ocular pressure-lowering medication. One or two eyes per patient may be enrolled.MethodsWe performed AS-OCTA (Nidek RS-3000 Advance 2, Gamagori, Japan) pre- and up to 6 months post-MIGS implantation using a standard protocol in all cornealimbal quadrants, to derive episcleral vessel densities (VD) using a previously described technique.Main Outcome MeasuresEpiscleral VD pre- and post-surgery, in sectors with and without the implant.ResultsWe obtained serial AS-OCTA images in 25 eyes undergoing MIGS implantation (23 subjects, mean age 70.3 ± 1.5, 61% female) with mean preoperative intraocular pressure (IOP) of 15.5 mmHg ± 4.0. We observed reductions in postoperative episcleral VD compared to preoperative VD at month 1 (mean difference −3.2, p = 0.001), month 3 (mean difference −2.94, p = 0.004) and month 6 (mean difference −2.19, p = 0.039) in sectors with implants (overall 6 month follow-up, p = 0.011). No significant changes were detected in episcleral VD in the sectors without implants (p = 0.910).ConclusionIn our pilot study, AS-OCTA was able to detect changes in the episcleral VD following trabecular bypass MIGS, which may be a useful modality to evaluate surgical outcomes if validated in future studies.
Highlights
Glaucoma is one of the leading causes of blindness worldwide [1]
The mean pre-operative intraocular pressure (IOP) was 15.5 ± 4.0 mmHg, with eyes being on an average of 1.2 glaucoma medications pre-operation, and mean Humphrey Visual Field (HVF) mean deviation (MD) was −4.9 ± 3.2 dB
All eyes had intra-operative identification of episcleral vessels after Hydrus Microstent implantation to confirm drainage of aqueous humour and intra-operative images were compared with corresponding anterior segment optical coherence tomography angiography (OCTA) (AS-OCTA) images at post-operative day 1 (Figure 3)
Summary
Glaucoma is one of the leading causes of blindness worldwide [1]. Increased intraocular pressure (IOP) is the main risk factor for glaucoma, and the mainstay of glaucoma treatment involves lowering of IOP [2, 3]. Conventional glaucoma surgeries such as trabeculectomy may effectively lower IOP, but can be associated with sight-threatening complications [5]. To address these limitations, minimally invasive glaucoma surgery (MIGS) has gained popularity in recent years. While MIGS is usually associated with a good safety profile, clinical results suggest variable efficacy in IOP reduction [8, 9]. Both iStent (Glaukos, San Clemente, CA, USA) and Hydrus Microstent (Ivantis Inc., Irvine, CA, USA) are ab interno trabecular bypass products that increase aqueous outflow, with the latter scaffolding and dilating the Schlemm’s canal as well. In a head-to-head study comparing Hydrus to iStent inject, the COMPARE study found Hydrus to have a greater rate of surgical success compared to iStent, with fewer subjects needing repeat glaucoma surgeries or medications [10]
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