Trabecular stent bypass microsurgery for open-angle glaucoma

Severe loss of corrected distance visual acuity (CDVA) was reported in 1 patient each in the combined group and in the phacoemulsification-only group in a randomised controlled trial (RCT) of 239 patients with open-angle glaucoma not controlled on 1 medication comparing stent insertion combined with phacoemulsification (n=116) against phacoemulsification alone (n=123). In the combined group, the loss of CDVA occurred after a stroke; in the phacoemulsification-only group, it occurred after macular traction, macular hole and macular oedema treated with vitrectomy. In the same study, CDVA worse than 20/40 was reported in 7 eyes in the combined group and in 9 eyes in the phacoemulsification group at 24‑month follow‑up. The causes reported were onset or progression of macular disease (n=6), posterior capsule opacification (n=2) and dry eye (n=2). Blurry vision or visual disturbance were also reported in 3% (4/116) of eyes in the combined group and in 7% (8/117) of eyes in the phacoemulsification-only group.

Increase in intraocular pressure (IOP) above 10 mmHg after the procedure was reported in 48% of patients in the combined group of 1 of the 32 studies included in a systematic review and meta-analysis of 2,143 patients with glaucoma and cataract comparing stent insertion combined with phacoemulsification against phacoemulsification alone. In the same systematic review, rise in IOP above 30 mmHg after the procedure was reported in 15% of patients in the combined group in 1 of the studies. Elevated IOP was reported in 10% of patients in 1 of the 5 studies included in a systematic review and meta-analysis of 248 patients treated by stent insertion alone.

Cystoid macular oedema was reported in 1% of patients in the combined group of 1 of the studies included in the systematic review and meta-analysis of 2,143 patients. Macular oedema was reported in 2% (1/50) of patients in the combined group and in 4% (2/50) of patients in the phacoemulsification-only group in an RCT of 100 patients comparing stent insertion combined with phacoemulsification (n=50) against phacoemulsification alone (n=50), during the first year of follow‑up.

Optic disc haemorrhage was reported in 1 patient in each of the combined groups in the RCTs of 239 patients and 100 patients, within 24 months and 1 year of follow‑up respectively.

Hyphema was reported in 2 to 4% of patients in 3 of the studies included in the systematic review and meta-analysis of 2,143 patients, and in 3% of patients in 1 of the studies included in the systematic review and meta-analysis of 248 patients.

Subconjunctival haemorrhage was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta-analysis of 2,143 patients, and in 1% of patients in 1 of the studies included in the systematic review and meta-analysis of 248 patients.

Anterior chamber collapse was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta-analysis of 2,143 patients. Hypotony was reported in 3% of patients in 1 of the studies included in the systematic review and meta-analysis of 248 patients.

Intraocular inflammation was reported in 1% of patients in 1 of the studies included in the systematic review and meta-analysis of 248 patients.

Cataract progression was reported in 3% (4/119) of patients (2 in the 1‑stent group and 2 in the 3‑stent group) in an RCT comparing implantation of 1 stent (n=38) against implantation of 2 stents (n=41) or 3 stents (n=40) in patients with primary open-angle glaucoma not controlled on ocular hypotensive medication; the patients were treated by cataract surgery.

Goniosynechiae or iris synechiae each were reported in 1% of patients in 1 of the studies included in the systematic review and meta-analysis of 248 patients. Focal peripheral anterior synechiae were reported in 30% (15/50) of patients in the combined group and in 4% (2/50) of patients in the phacoemulsification-only group in the RCT of 100 patients within 2 years of follow‑up.

Vitreous wick incarcerated in paracentesis was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta-analysis of 2,143 patients.

Vitreomacular traction was reported in 2% (1/50) of patients in each group in the RCT of 100 patients within 2 years of the procedure.

Posterior capsule opacification was reported in 3% and 1% of patients and in 6% (7/116) of eyes in the combined group in 1 of the studies included in the systematic review and meta-analysis of 2,143 patients, in the systematic review and meta-analysis of 248 patients and in the RCT of 239 patients respectively, within 24 months of the procedure.

Epiretinal membrane was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta-analysis of 2,143 patients.

Iris atrophy was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta‑analysis of 2,143 patients.

Uveitis (iritis) was reported in 2% of patients and in 1 (n=116) eye treated by stent insertion and phacoemulsification in the systematic review and meta-analysis of 2,143 patients and in the RCT of 239 patients respectively.

Dry eye was reported in 2% of patients in the combined group in 1 of the studies included in the systematic review and meta‑analysis of 2,143 patients. Soreness or discomfort was reported in 1 patient in an RCT of 192 patients comparing implantation of 2 stents (n=94) against medical therapy (n=98); this was treated with non-steroidal anti-inflammatory medications.

Descemet folds were reported in 1 patient in each group at 1‑month follow‑up in the RCT of 100 patients; they resolved before the 3‑month follow‑up visit.

In the systematic review and meta-analysis of 2,143 patients, stent malposition was reported in 2 to 18% of patients in 6 studies, stent occlusion was reported in 4 to 15% of patients in 4 studies and blockage of the opening of the stent lumen was reported in 15% of patients in 1 study.

In the systematic review and meta-analysis of 248 patients, a need to reposition the stent was reported in 2% of patients in 1 study, stent not visible upon gonioscopy was reported in 13% of patients in 1 study, and stent replacement was reported in 5% of patients in 1 study.

Secondary surgical interventions were needed in 4% (5/116) of eyes in the combined group and in 5% (6/117) of eyes in the phacoemulsification-only group in the RCT of 239 patients, within 24 months of follow‑up (including patients who had more than 1 surgical re‑intervention). In the combined group of 116 patients, the secondary surgical interventions were stent repositioning (3% [3/116]), stent removal and replacement (1 patient), Nd:YAG laser for stent obstruction (1 patient), trabeculoplasty (1 patient) and focal argon laser photocoagulation (1 patient). Secondary glaucoma surgery was reported in 1 patient in the combined group and in 2 patients in the phacoemulsification-only group in the RCT of 100 patients during the second year of follow‑up.

In addition to safety outcomes reported in the literature, specialist advisers are asked about anecdotal adverse events (events which they have heard about) and about theoretical adverse events (events which they think might possibly occur, even if they have never done so). For this procedure, specialist advisers listed the following anecdotal adverse event: stent dislocation. They considered that the following was a theoretical adverse event: stent movement during MRI scan.