The purpose of this study is to evaluate the middle-term tonometric results of a new filtering procedure, the nonpenetrating deep sclerectomy with or without collagen device, in primary open-angle glaucoma. This technic aims to eliminate or minimize the complications of classical trabeculectomy.
Method: This procedure was carried out by Koslov and colleagues. This is performed under a limbal-based conjunctival flap and a superfical scleral flap, the ablation of a deep scleral flap taking away the external wall of Schlemm's canal, only living in place the Descemet membrane. One must obtain a visible filtration across the opened Schlemm's canal and Descemet membrane. To improve the aqueous filtration, a cylindric collagen device, made from porcine scleral tissue, biocompatible, known for its high water content, is fixed in the deep scleral bed with a 10/0 nylon suture. This device provides a support for the elimination route of aqueous humor and acts like a sponge, carrying the liquid by capillary action. It is sterilized by irradiation. Full guarantee against viral contamination is provided. This procedure ends in one suture (10/0 nylon) of superficial scleral flap and conjunctival closing suture. When NPDS is performed without CD a sponge of 5FU is used and the superficial scleral flap is not sutured.
Retrospective study: Our material included 111 patients, 148 eyes in CD group; 43 patients, 55 eyes in the group without CD. The average follow-up was 13.3 +/- 5.8 months in the CD group, 7.2 +/- 3.5 months in the group without CD. All patients presented a POAG without risk factors of bleb failure.
Results: The delta average IOP before the operation and at the end of the follow-up period was 7.2 +/- 6.3 mmHg in the CD group; 8.3 +/- 7.6 mmHg in the group without CD (no significant difference). The probability-success rate with the Kaplan-Meier method (IOP < or = 20 mmHg) was, in the CD group, at 18 months, 68% and 69% in the group without CD, without medical treatment. With monotherapy, the success rate was 85% in the CD group, 74% in the group without CD (p < or = 0.05).
Prospective study: Afterwards, we have conducted a prospective study comparing two groups of patients with POAG without risk factors of bleb failure, operated with and without collagen device, without 5FU in the second group. Our material included 31 patients, 31 eyes, one eye for each patient, two surgeons; 17 eyes in the CD group, 14 eyes in the group without CD. The average age was 65.8 +/- 8.2 years in the first group; 64.1 +/- 10.3 in the second group. The average follow-up was 11 months in both groups.
Results: delta average IOP was 8.3 +/- 5.8 in the CD group; 12.3 +/- 6 in the group without CD (p < 0.05). The probability-success rate without treatment at 12 months: 58% in the first group, 90% in the second group (p < 0.05) and with monotherapy: 80% and 90% (N.S.). In both studies, in both groups, except microperforations, more frequent in the prospective group without CD, no complications of the trabeculectomy were observed. The mean change in visual acuity was inferior to 0.1 at the end of the follow-up. A postoperative rise in IOP can occur. It can be due to an internal obstruction (goniosynechiae or bad filtration). It can be treated with Nd-Yag laser. It can also be due to external obstruction, treated by 5FU injections into the bleb. The success of these procedures were similar in the whole group.
Conclusion: Non penetrating deep sclerectomy can be considered as an excellent alternative to trabeculectomy in open and wide angles. It does not modify visual acuity. It carries away less complications than trabeculectomy and the use of antimitotic agents is safer. Collagen device does not seem, at middle-term, to improve tonometric results.