Ab interno trabeculectomy
Removal of trabecular tissue with small-gauge vitreous cutter effective in lowering IOP
Adrian Gavanescu MD
Early results with an ab interno trabeculectomy technique performed with a 23-gauge vitreous cutter under gonioscopic view can produce substantial intraocular pressure (IOP) reductions in patients with open-angle glaucoma, according to Adrian Gavanescu MD, of Clinical Hospital Nicolae Malaxa, Bucharest, Romania.
“This is an internal filtering procedure involving the excision of trabecular meshwork tissue and leaving a large distance between edges to prevent scarring and fibrosis,” said Dr Gavanescu in a poster presentation at the XXXIV Congress of the ESCRS in Copenhagen, Denmark.
He presented the results achieved in 17 open-angle glaucoma patients who underwent the ab interno trabeculectomy procedure, with or without cataract surgery.
In the five patients who underwent the procedure in combination with cataract surgery, the mean IOP at six months follow-up was 13.5mmHg. That compared to 21.6mmHg preoperatively and amounted to a 37.5% reduction. Among those who underwent ab interno trabeculectomy alone, the mean IOP was 14.5mmHg at six months. That compared to 26mmHg preoperatively and amounted to a 44.24% reduction.
In addition, all patients were able to maintain their low pressures throughout follow-up without further use of IOP-lowering medications. The only postoperative complication was hyphaema which occurred in two patients but disappeared within eight to 10 days.
The selective ab interno trabeculectomy procedure begins with the creation of two 1.0mm near-limbal corneal incisions with a 20-G lance knife, one at 2 o’clock for the anterior chamber maintainer and the other at 10 o’ clock for insertion of the vitreous cutter. A miotic agent is then used to obtain better access to the angle.
The next step is to visualise the trabecular meshwork using a goniolens. If the pigmented portion of the meshwork is still not visible, inducing hypotony will enable visualisation of Schlemm’s canal.
The goniolens is then removed and the vitreous cutter inserted into the anterior chamber. The goniolens is then replaced on the cornea and the vitreous cutter’s tip is advanced until it makes contact with the trabecular meshwork.
The surgical technique has evolved since the time of the poster presentation at the XXXIV Congress of the ESCRS, from two 1mm incisions to one 2.2mm incision that can accommodate both the vitreous cutter with a special irrigator on top, to maintain the anterior chamber depth
After gently pressing the iris, the surgeon inserts the tip of the vitreous cutter into the meshwork and activates its infusion/aspiration and cutting functions to ablate an arc of 30 to 90 degrees of trabecular meshwork tissue and the inner wall of Schlemm’s canal.
The patient’s postoperative regimen includes pilocarpine, one drop four times a day for two months; dexamethasone, one drop four times a day for two weeks; and netilmicine, one drop four times a day for two weeks.
This new procedure was also presented at the 20th ESCRS Winter Meeting in Athens, Greece, the 12th European Glaucoma Society Congress in Prague, Czech Republic, and at DOG 2016 in Berlin, Germany.
The surgical technique has evolved since the time of the poster presentation at the XXXIV Congress of the ESCRS, from two 1mm incisions to one 2.2mm incision that can accommodate both the vitreous cutter with a special irrigator on top, to maintain the anterior chamber depth.
Adrian Gavanescu: firstname.lastname@example.org
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