The Importance Of Supraciliary Implant Surgical Positioning Assessed By Ultrasonic Biomicroscopy And Its Association With Intraocular Pressure And Safety Outcomes

Devices utilizing the supraciliary space can provide a long-term intraocular pressure (IOP) decrease and aqueous outflow via the uveoscleral pathway. Success may depend on risks of device malposition or migration. Ab-interno placement of such devices can result in partial intraciliary placement, instead of supraciliary. A novel cilioscleral interposition device (CID), implanted using an ab-externo surgical technique, seeks to mitigate these risks, without involving the iridocorneal angle.  Device position observed by ultrasonic biomicroscopy (UBM) and its relationship with IOP in a cohort of patients implanted with CID out to twelve months with primary open-angle glaucoma (POAG) and primary angle closure glaucoma (PACG) was assessed.

A single center, single surgeon, prospective, clinical study in Yerevan, Armenia which completed recruitment in 2022 (clinicaltrials.gov ID NCT05236439).

The CID was implanted in patients with a diagnosis of POAG or PACG (Shaffer 1-4) requiring surgical intervention due to inadequate topical therapy. Two full-thickness scleral incisions 2 mm from the surgical limbus were made enabling ciliary muscle view. The CID is made of flexible hydrophilic acrylic and implanted by sliding it into an OVD-created subscleral space, over the ciliary muscle. OVD was then removed and scleral incisions sutured. Topical hypotensives were discontinued postoperatively. Expert reviewers assessed latest available postoperative outcomes (range M6 to M24) of IOP, adverse events, and UBM. UBM position was assessed by observing device location in relation to anatomical landmarks, and areas of hypoechogenicity.

Mean IOP at baseline in the intent-to-treat cohort of fifty-six patients (mean age 64.8 ±11.1 years) was 23.5±1.7mmHg at baseline, which reduced to 14.2±3.2mmHg postoperative. Hypoechogenic area classification lateral to CID was associated with lower postoperative mean IOP (largest area seen in 10 subjects, mean IOP 10.5±3.0 mmHg). UBM review demonstrated no instances of intraciliary device placement, nor any cases of postoperative device migration. POAG and PACG outcomes were similar.  There were no serious adverse events, no clinically significant hypotony, and no evidence of fibroses on UBM. A single case of device rupture of the iris root occurred during surgery, but the device position was stable at M12.

CID implantation was efficacious for POAG and PACG patients alike in this study with a substantial and sustained IOP reduction out to M24 in some cases.  The CID surgical implantation technique supported long term positional stability in the supraciliary space, without migration or fibrosis. A larger area of hypoechogenicity on UBM was associated with lower IOP. Safety was overall favorable. The use of an ab-externo versus ab-interno surgical approach ensured proper supraciliary placement, and prevented complications related to anterior chamber penetration.  This makes CID a promising option, which still preserves the option of future traditional surgery.