Goniocurettage for removing trabecular meshwork: clinical results of a new surgical technique in advanced chronic open-angle glaucoma

[Results of combined endotrabeculectomy and phacoemulsification surgery]

AIM

to identify indications and evaluate the efficacy of combined endotrabeculectomy and phacoemulsification surgery.

MATERIAL AND METHODS

A total of 172 patients (193 eyes) with open-angle glaucoma and cataract were enrolled. Group 1 included 102 patients (118 eyes), who were considered surgical candidates due to decompensation of IOP, group 2--70 patients (75 eyes), in whom IOP control could only be achieved with a multidrug regimen (two or more ocular hypotensive medications). The mean preoperative IOP measured with Maklakov tonometer was 26.4 ± 1.8 mmHg in group 1 and 20.5 ± 1.7 mmHg in group 2. In 134 eyes the extent of retention of intraocular fluid was determined intraoperatively by provoking blood reflux into Schlemm's canal.

RESULTS

In 6 out of 134 eyes (4.5%) Schlemm's canal was not at all filled with blood, which was considered a contraindication for endotrabeculectomy. Partial filling of Schlemm's canal with blood was observed in 26 out of 134 eyes (19.4%), complete--in 102 eyes (76.1%). All but 6 patients underwent endotrabeculectomy (ab interno trabecular excision with original forceps through the anterior chamber angle) combined with cataract phacoemulsification and intraocular lens implantation. In 11 out of 126 cases, insignificant bleeding occurred during sample acquisition. No other complications were registered. Six months after the surgery, IOP was reduced by the mean of 7.0 ± 0.6 mmHg (26.5% from the baseline) in group 1 and by 2.2 ± 0.2 mmHg (10.7% from the baseline) in group 2. The number of hypotensive medications by that time has been decreased from 2.3 ± 0.3 to 0.8 ± 0.2 in group 1 and from 1.6 ± 0.3 to 0.4 ± 0.1 in group 2.

CONCLUSION

Combined endotrabeculectomy and phacoemulsification surgery is a pathogenically oriented procedure, which improves ocular hydrodynamics and has a significant hypotensive effect.

Ab interno trabeculectomy in the adult patient

Glaucoma is a potentially blinding disease that affects millions of people worldwide. The mainstay of treatment is lowering of intraocular pressure (IOP) through the use of medications, laser and/or incisional surgery. The trabecular meshwork (TM) is thought to be the site of significant resistance to aqueous outflow in open angle glaucoma. Theoretically, an incision through TM or TM removal should decrease this resistance and lead to a significant reduction in IOP. This approach, commonly referred to as goniotomy or trabeculotomy, has been validated in the pediatric population and has been associated with long-term IOP control. In adults, however, removal of TM tissue has been historically associated with more limited and short-lived success. More recent evidence, reveals that even adult patients may benefit significantly from removal of diseased TM tissue and can lead to a significant reduction in IOP that is long-lasting and safe. In this review, we discuss current evidence and techniques for ab interno trabeculectomy using various devices in the adult patient.

Preclinical investigation of ab interno trabeculectomy using a novel dual-blade device

PURPOSE

To evaluate the effects of a novel ab interno trabeculectomy device on human trabecular meshwork (TM).

DESIGN

Laboratory evaluation.

METHODS

The TM from human cadaveric corneal rim tissue was incised using 3 instruments: (1) novel dual-blade device; (2) microvitreoretinal (MVR) blade; and (3) Trabectome. Tissue samples underwent histologic processing and comparative analyses. Subsequently, human eye perfusion studies were performed to evaluate intraocular pressure (IOP)-lowering effects of each device. Main outcome measures were degree of TM removal by histology and IOP in a perfusion model.

RESULTS

The MVR blade exhibited minimal removal of TM and obvious injury to the adjacent sclera. The Trabectome removed a large portion of the central TM, but leaflets of residual tissue remained and thermal injury was noted in all samples. The dual-blade device achieved a more complete removal of TM without injury to surrounding tissues. All devices resulted in statistically significant lowering of IOP during perfusion model studies. MVR blade treatment across 170.0 ± 14.1 degrees of TM resulted in a decrease of IOP from 18.5 ± 1.9 mm Hg to 12.8 ± 2.2 mm Hg (P < .01). Trabectome treatment across 117.5 ± 12.6 degrees resulted in a decrease of IOP from 18.8 ± 1.7 mm Hg to 11.3 ± 1.0 mm Hg (P < .01). Dual-blade device treatment across 157.5 ± 26.3 degrees resulted in a decrease of IOP from 18.3 ± 3.0 mm Hg to 11.0 ± 2.2 mm Hg (P < .01).

CONCLUSIONS

The novel dual-blade device demonstrated a more complete removal of TM without residual TM leaflets or damage to surrounding tissues and significantly reduced IOP in a human eye perfusion model.

Endoscopically controlled goniosynechialysis in managing synechial angle-closure glaucoma

PURPOSE

To propose a new surgical technique for optimized visualization of the chamber angle using ophthalmic microendoscope in goniosynechialysis (GSL).

METHODS

Patients who had acute angle-closure glaucoma with peripheral anterior synechiae or patients with flat anterior chamber after trabeculectomy underwent endoscopically controlled GSL. Ophthalmic endoscope was used before, during, and immediately after GSL to minimize the procedure of GSL and to ensure that the trabecular meshwork was exposed and the majority of the angle was opened after endoscopically controlled GSL. Intraoperative complications, postoperative visual acuity, intraocular pressures (IOPs), and complications were all evaluated.

RESULTS

Twelve eyes of twelve patients underwent the operation and the mean follow-up was 7.4+/-1.4 months (range: 6 to 10 mo). The mean preoperative IOP was 42.89+/-15.81 mm Hg. The mean postoperative IOP at the most recent follow-up was 12.72+/-3.48 mm Hg. The absolute success rate (IOP <21 mm Hg without medication) was 8 of 10. Visual acuity improved in 11 of 12 patients (91.7%). No significant intraoperative complications, such as iridodialysis, occurred in any patient. Postoperative complications included hyphema and transient corneal decompensation.

CONCLUSIONS

Endoscope conveniently provided the surgeon an optimized visualization of the anterior chamber angle. This enhanced visualization and convenience promises accuracy and safety when performing GSL.

Trabecular bypass stents decrease intraocular pressure in cultured human anterior segments

PURPOSE

To determine the effect on intraocular pressure (IOP) of bypassing the trabecular meshwork in cultured human anterior segments.

DESIGN

Prospective laboratory investigation using normal human eyes obtained at autopsy.

METHODS

Anterior segments from 21 eyes were placed in perfusion culture, and trabecular bypass stents were inserted through the trabecular meshwork, with the lumen of the tube opening into Schlemm's canal. Eyes received from one to four stents, placed equidistant apart. In eyes receiving one or two stents, additional stents were later added to a maximum of four per eye.

RESULTS

Intraocular pressure was lowered after placement of a single stent, from 21.4 +/- 3.8 mm Hg to 12.4 +/- 4.2 (P < .001). This corresponded to an 84% increase in facility of outflow. Eyes receiving more than one stent had final IOP of 11.9 +/- 3.7 mm Hg. Nine eyes had sequential addition of stents, and seven of these had a further decrease of IOP (13.6 +/- 4.1 to 10.0 +/- 4.3; P = .02). Excision of the entire meshwork, between stents, dropped IOP to 6.3 +/- 3.2 mm Hg, indicating some residual meshwork or canal resistance remained even after placement of three stents.

CONCLUSIONS

Bypass of the trabecular meshwork lowers IOP in cultured human anterior segments. One stent produced the greatest change in pressure. The sequential addition of more stents further lowered pressure in seven of nine eyes. This technique holds promise as a new clinical surgery for glaucoma.

How does nonpenetrating glaucoma surgery work? Aqueous outflow resistance and glaucoma surgery

Histologic, experimental, and theoretical studies of the aqueous outflow pathways point toward the juxtacanalicular region and inner wall of Schlemm's canal as the likely site of aqueous outflow resistance in the normal eye. At least 50% of the aqueous outflow resistance in the normal eye and the bulk of the pathologically increased resistance in the glaucomatous eye resides in the trabecular meshwork and the inner wall of Schlemm's canal. The uveoscleral, or uveovortex, pathway, which accounts for perhaps 10% of the aqueous drainage in the healthy aged human eye, can become a major accessory route for aqueous drainage after pharmacologic treatment. Surgeries designed to incise or remove the abnormal trabecular meshwork of glaucoma address the pathologic problem of the disease. Surgeries that unroof Schlemm's canal or expand the canal, such as viscocanalostomy, probably cause inadvertent ruptures of the inner wall and juxtacanalicular tissue, thus relieving the abnormal outflow resistance of glaucoma. This review is a summary of current thought on the pathophysiology of aqueous outflow resistance in glaucoma and, in light of this, provides an interpretation of the mechanism of pressure reduction created by these new surgeries.

Endoscopic surgery in glaucoma management

Endoscopically-controlled intraocular surgery has been evolving rapidly since the introduction of thinner endoprobes with increasing resolving power and higher image quality. Currently, anti-glaucomatous surgery is also beginning to take advantage of this exciting new technology. This article discusses the two main approaches to glaucoma management using microendoscopic techniques-decreasing aqueous humor production by means of laser endoscopic cyclophotocoagulation and increasing outflow facility through endoscopically-controlled selective trabecular surgery. Besides presenting clinical results, emphasis is placed on different surgeons' accounts of intraoperative endoscopic maneuverability and the spectrum of complications that may be attributed to the endoscopic nature of the surgical intervention.