New AB externo device shows promise

The ab externo implantation of a new Schlemm’s canal expanding device, the Kumar SCE-2, combined with a standard cataract procedure has a good safety profile and can produce dramatic reductions in intraocular pressure (IOP) in patients with cataracts and glaucoma, according to the results of a study presented by Galina Dushina MD at the XXXIII Congress of the ESCRS in Barcelona, Spain.

“The combined surgery resulted in significant reductions in IOP and the use of hypotensive medication from baseline without any major complications,” said Dr Dushina, Department of Ophthalmology, Peoples’ Friendship University of Russia Medical Institute, Moscow.

The uncontrolled non-randomised interventional case series involved 19 eyes of 19 patients with cataracts and open-angle glaucoma who underwent the combined procedure. The patients had a mean age of 73.3 years, all had an IOP greater than 21mmHg on maximal anti-glaucoma medication, and all had a follow-up of more than 18 months following implantation of the Schlemm's canal expander.

The World Glaucoma Association’s criteria for complete success – a decrease in IOP greater than 20 per cent or IOP of 18mmHg or less without medication – was achieved in seven (47 per cent) of 15 patients at six months and in four (33 per cent) of 12 patients at 12 months. Partial success – the same IOP reductions but with the use of anti-glaucoma medications – was achieved in 40 per cent of patients at six months and 50 per cent of patients at 12 months.

In addition, mean IOP was decreased by 41.1 per cent from a preoperative value of 23.1mmHg to 11.8mmHg at six months (p = .0000007), and by 45.4 per cent from a preoperative value of 23.6mmHg to 12.5mmHg at 12 months (p = .000001). Furthermore, the mean number of IOP-lowering medications patients used fell from 2.6 preoperatively to 0.7 at six months (p = .0000001) and 1.1 at 12 months (p = .0008).

The Kumar SCE-2 consists of a coil of 0.04mm-thick medical grade stainless steel wire, 2.5mm to 3.0mm in length with an inner lumen diameter of 0.12mm, and a curvature like that of Schlemm’s canal. The SCE-2 is the second generation of the Kumar SCE and was developed by Kumar Vinod MD, PhD, Mikhail Frolov MD, PhD, Dr Dushina and Elena Bozhok MD. The Peoples' Friendship University of Russia Medical Institute, Moscow holds the patent for the device.

THREE STAGE PROCEDURE

Dr Dushina and her associates performed the combined glaucoma and cataract procedure in three stages. The first stage is similar to deep sclerectomy, with the creation of scleral flaps and the unroofing of 3.0mm of Schlemm’s canal, although without the creation of a Descemet’s window. The second step is the phacoemulsification of the cataract and the implantation of the intraocular lens.

The final stage involves the viscodilation of a 5.0mm to 6.0mm segment of Schlemm’s canal with a cohesive ophthalmic viscosurgical device, followed by the insertion of the canal expanding device, mounted on a specially designed and similarly curved 0.2mm-diameter stainless steel microprobe into the ostia of Schlemm’s canal. Once the scleral expanding device is in place, the probe is removed, leaving the Schlemm’s canal expander behind. The procedure is concluded with the watertight closure and suturing of the scleral and conjunctival flaps.

Intraoperative complications included five cases of microperforation due to inadequate viscodilation of Schlemm’s canal and one case of posterior capsule rupture (five per cent). Postoperatively, two cases (10 per cent) required YAG laser trabeculopuncture to control IOP. There were no cases of hypotony, endophthalmitis or shallow anterior chamber. In addition, there was not a single case of inflammation at the insertion site.

“We found that the implant was easy to implant and that patients had a rapid rehabilitation. Randomised controlled and comparative studies with longer follow-up and larger groups are required in order to confirm the efficacy of the technique,” Dr Dushina concluded.

Galina Dushina: dushina_galina@mail.ru