REFRACTORY PRIMARYOPEN-ANGLE GLAUCOMA

Segment dilation of Schlemm’s canal using a novel stainless steel spiral expander appears safe and effective for reducing intraocular pressure (IOP) and medication use in patients with medication-refractory primary open-angle glaucoma, reported Galina Dushina MD at the XXXII Congress of the ESCRS in London.

The intracanalicular device is patented in Russia and was designed and developed by a group of inventors at the ophthalmic unit of Skhodnya Hospital and Department of Ophthalmology, Medical Institute, Peoples’ Friendship University of Russia: Kumar Vinod MD, PhD, Frolov Mikhail MD, PhD, Dr Dushina and Bozhok Elena MD. It is made of 0.05-mm thick, medical grade soft vanadium stainless steel wire that is wound around a 0.2mm stainless steel microprobe to create a spiral having the same curvature as Schlemm’s canal.

Dr Dushina presented one-year outcomes from 12 eyes with preoperative IOP above 21mmHg on maximum IOP-lowering medication. In two patients who had end-stage glaucoma, the surgery was performed to salvage the eye, and five patients underwent concomitant cataract surgery.

Mean IOP was 25.1mmHg preoperatively, 11.2mmHg at one month postoperatively, and 13.4mmHg at 12 months, a 46 per cent reduction from baseline. The surgery was judged a complete success (IOP reduction >25% or ≤18mmHg without medication) in five eyes, and the remaining seven eyes met criteria for partial success (same IOP thresholds with medication use). Mean daily medication use decreased from 2.4 preoperatively to 1.1 at 12 months. Of the seven patients on medication, three were using a single drop, one was on two drops, and three were on three medications.

“There is early rehabilitation with this surgery, and we have not seen any serious complications or inflammation at the insertion site. Now, randomised controlled studies with longer follow-up and larger patient populations are required to confirm the efficacy and safety of this technique,” said Dr Dushina, Department of Ophthalmology, Peoples’ Friendship University of Russia, Moscow.

Watertight closure

The ab externo surgery involves exposure of a 3.0mm area of Schlemm’s canal with a technique similar to that used for deep sclerectomy but without creating a window in Descemet’s membrane. After first dilating a 5 to 6.0mm segment of unexposed Schlemm’s canal with a cohesive viscoelastic and microprobes with diameters 0.2 to 0.3mm, the expander device is mounted on a microprobe for insertion. Watertight closure of the deep and superficial scleral flaps and conjunctival flap is verified at the end of the procedure.

“Insertion of the device into the canal is the only new element of this viscocanalostomy surgery, and it was easily done except in one patient who had previous glaucoma surgery,” Dr Dushina observed.

However, microperforation of the trabecular meshwork at unexposed sites of Schlemm’s canal occurred intraoperatively in three eyes due to insufficient dilation of the canal. In the latter cases, one end of the device resided in the anterior chamber angle, but it was not touching any tissue.

The only other device-related event occurred postoperatively at a second follow-up visit when pressure during examination with a gonio lens caused the body of the device to dislocate into the angle. The two ends remained embedded in Schlemm’s canal, and the patient’s IOP was controlled at one year with
use of one medication and no evidence of inflammation.

Galina Dushina: dushina_galina@mail.ru