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Editors Selection IGR 7-3
Surgical treatment: Progress in trabecular surgery
Comment by Franz Grehn on:
12463 Clinical results with the Trabectome for treatment of open-angle glaucoma, Minckler DS; Baerveldt G; Alfaro MR et al., Ophthalmology, 2005; 112: 962-967
Minckler et al. (675), report on results of trabecular surgery with the new Trabectome® (NeoMedixCorp, San Juan Capistrano, California, USA) in 37 eyes. The rationale of this device is to probe Schlemm's canal ab interno and to ablate the trabecular meshwork and the inner wall of Schlemm's canal by electrocautery. This instrument uses infusion and aspiration to remove ablated debris and can aspirate blood reflux from the canal during the procedure. A semicircle of 30 to 60 degrees can be treated in the nasal circumference of the trabecular meshwork from a temporal approach under gonioscopic view with the instrument. Viscoelastics during surgery, air tamponade, and corneal suture of the corneal incision were helpful.
Removal of trabecular meshwork can effectively reduce the intraocular pressure in open angle glaucoma
The IOP was reduced from a preoperative value of 28.2 mmHg without medication to 17.6 at 6 months and to 16.3 mmHg at 12 months postoperatively. Hyphema was present in 59% but cleared at a mean of 6.4 days postoperatively. Focal peripheral anterior synechiae were found in 24.3 %. Pilocarpine seems to be helpful in sheltering the lens during surgery and pulling open the cleft after surgery. Visual acuity remained constant for the period follwed. Postoperative IOP was maintained with 0.3 medications as compared to 1.2 medications preoperatively.
This study proves that removal of trabecular meshwork can effectively reduce the intraocular pressure in open angle glaucoma. This technique is attractive because the device ablates trabecular meshwork and keeps the lumen of the canal open, whereas trabeculotomy ab externo or goniotomy which open the trabecular meshwork by incision may fail due to trapdoor closure of the flap of the incised trabecular meshwork. When compared to modern trabeculectomy with Mitomycin-C, this new procedure has a favourable outcome in regard to complication rate. The IOP values achieved are, however, higher than in MMC trabeculectomy. In the first 3 months, the resulting mean IOP (with a 2/3 follow up of cases) was about 17.3 mmHg, and after 1 year (with onlly 40% follow up), the IOP was 16.3 mmHg. However, this method does not alter the conjunctiva and can be followed by filtration surgery if needed.
The comparison to other trabecular surgical methods is attractive: Trabecular aspiration (Jacobi & Krieglstein) is effective particularly in pseudoexfoliative glaucoma, but there is regression of the effect with time. Goniocurretage (Jacobi & Krieglstein) removes trabecular meshwork mechanically and seems to have a higher incidence of bleeding. Trabecular laser ablation with the Excimer laser (ELT) (Funk) creates openings into Schlemms canal and is particularly helpful as an adjunctive procedure in combined cataract/glaucoma cases. The Glaucos-stent yields in moderate IOP decrease when using 2 stents (Douglas Johnson). Classical trabeculotomy in adults is also effective, possibly through microfiltration (Dannheim & Harms, Tanihara). There is a vast body of literature on adult trabeculotomy, which shows that resulting IOP is in the range of all trabecular surgical methods, i.e. generally above 15 mmHg. Trabeculotomy is also suited for combined procedures.
The present study supports the view that this method may have future application in those open angle glaucoma cases that do not need very low IOPs. This prospective case series should support future work which might compare this method to classical trabeculectomy in a randomized trial.
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