Deep sclerectomy with a collagen implant using the excimer laser

Clinical application of the CO2 laser in Ab externo Schlemm's canal surgery

Purpose

This study aimed to investigate the clinical application of laser as a knife in Ab externo Schlemm's canal (SC) surgery and compare the efficacy and safety of the CO₂ laser with the conventional procedure using a surgical knife.

Methods

Patients who underwent either canaloplasty or trabeculotomy with CO₂ laser system which was used to locate and ablate the outer wall of SC at the time interval between May 2020 and May 2021 were identified, their medical files were reviewed, and their results were compared with conventional surgery group who underwent canaloplasty or trabeculotomy with conventional surgical knife at the same time period. The following datas were conducted and compared: age, sex, intraocular pressure (IOP), number of drugs, best-corrected visual acuity (BCVA), mean deviation and pattern standard deviation of visual field examination, SC opening related complications.

Results

A total of 49 patients (49 eyes) were included in this study, including 23 in the Laser surgery group and 26 in the conventional surgery group. Time for SC opening was 49.33 ± 25.23 s and 116.50 ± 31.79 s for laser surgery group and conventional surgery group, respectively. This difference between the two groups was statistically significant (P < 0.01). Hemorrhage occurred in five eyes during ablation for the laser surgery group and in 24 eyes for the conventional surgery group. In addition, anterior chamber penetration occurred in two cases for the laser surgery group and in six cases for the conventional surgery group. The success rate of identifying and opening outer wall of SC was 91.30% (21 eyes) for the laser surgery group and 76.92% (20 eyes) for the conventional surgery group. The difference between preoperative and postoperative intraocular pressure for each group was statistically significant (P < 0.01), and there were no statistically significant differences across the two groups in terms of postoperative IOP (P = 0.238) and BCVA (P = 0.389).

Conclusion

Compared with the conventional procedure using a surgical knife, CO₂ laser-assisted ablation of the outer wall of SC was less time-consuming and less technically challenging. CO₂ laser-assisted ablation also resulted in fewer complications. Furthermore, it had a shorter learning curve and a higher success rate of identifying and opening SC.

Prospective evaluation of CO2 laser-assisted sclerectomy surgery (CLASS) with Mitomycin C

PURPOSE

Our purpose was to evaluate the clinical safety and efficacy of CO₂ laser-assisted sclerectomy surgery (CLASS) with Mitomycin C (MMC) in open angle glaucoma (OAG).

METHODS

This was a prospective, uncontrolled, interventional case series. All subjects underwent CLASS procedure by a single surgeon. After the dissection of a partial thickness scleral flap, topical MMC 0.2 mg/ml was applied to the sclera and the conjunctiva for 3 min. The CO₂ laser with a beam-manipulating system was used to ablate the scleral tissue and expose the Schlemm's canal area. Primary outcomes: intraocular pressure (IOP) change, number of IOP-lowering medicaments change. Adverse events were evaluated as secondary outcomes.

RESULTS

Twenty-one eyes of 21 patients underwent the CLASS procedure. Thirteen were primary OAG (62%), two normal pressure glaucoma (10%), three exfoliative glaucoma (14%) and three others secondary OAG. With a mean (SD) follow-up of 15.3 (5.9) months, the IOP changed from 25.4 (6.7) mmHg at baseline to 10.9 (3.4) mmHg al the last visit. Mean reduction of IOP was -14.5 mmHg (95% CI, -17.7 to -11.2, P < 0.001). The median (IQR) number of IOP-lowering medication decreased from 3 (3-3) at baseline to 1 (0-1) at the last visit (P < 0.001). Visual acuity did not change significantly. Adverse events: five eyes (24%) developed iris adhesion to the filtration area that was successfully managed with office-based procedures. In one case (5%), CLASS was converted to trabeculectomy due to intraoperative perforation of the ablated area. There was one case of hypotony maculopathy successfully treated with placement of additional transconjunctival scleral flap sutures.

CONCLUSIONS

The CLASS procedure with MMC is clinically safe and effective maintaining a large reduction in IOP and in the number of IOP-lowering medications with a mean follow-up of 15 months. Iris adhesion at the filtrating area warrants further evaluation and possibly reflects the surgeon's learning curve.

Glaucoma surgery: taking the sub-conjunctival route

We are currently in the midst of a surge in interest in glaucoma surgery. Novel pathways for reducing intraocular pressure (IOP) have been tried with various levels of success over the last few years. While the trabecular bypass and suprachoroidal approaches have captured much of the attention, filtering aqueous into the sub-conjunctival space remains the gold standard for lowering IOP. This review attempts to focus on current research in surgical methods to enhance filtration by potentially improving on tried and tested methods like the trabeculectomy, deep sclerectomy, and tube surgeries.

The SuperCrescent diamond knife: an innovative blade for glaucoma surgery

Diamond blades have been used extensively in cataract surgery but their routine use in glaucoma surgery has been limited owing to the lack of controlled sharpness. The SuperCrescent knife is an ultrathin (100 μm) diamond blade that is an innovative modification of conventional blade design. Its pentium faceted trapezoidal design along with the square front surface area affords better control during dissection and has been used with success in both traditional trabeculectomies and nonpenetrating glaucoma procedures.

Nonpenetrating glaucoma surgery

Nonpenetrating glaucoma surgeries have been developed in recent years in order to improve the safety of conventional filtering procedures. The goal of nonpenetrating filtering procedures is to reduce intraocular pressure by enhancing the natural aqueous outflow channels, while reducing outflow resistance located in the inner wall of the Schlemm's canal and the juxtacanalicular trabecular meshwork. In the last few years viscocanalostomy and deep sclerectomy with external trabeculectomy have become the most popular nonpenetrating filtering procedures. Both involve removal of a deep scleral flap, the external wall of Schlemm's canal and corneal stroma behind the anterior trabeculum and Descemet's membrane, thus creating an intrascleral space. The aqueous humour leaves the anterior chamber through the intact trabeculo-Descemet's membrane into the scleral space, from where it will egress into different pathways. The technique is associated with a long learning curve. Published clinical trials comparing nonpenetrating glaucoma surgery to full-thickness trabeculectomy have a consensus on the superior safety profile of nonpenetrating glaucoma surgery but are not in agreement when it comes to efficacy, where conflicting results have been found. This article reviews the nonpenetrating surgical techniques, mechanisms of action, indications, contraindications, complications, and results.

CO2, excimer and erbium:YAG laser in deep sclerectomy

PURPOSE

Deep sclerectomy is a non-penetrating filtering procedure that is not generally accepted, as tissue dissection is difficult and varying success rates have been reported. The purpose of the present study was to compare the use of CO2, excimer and erbium:YAG lasers in dissection of the deep corneoscleral lamella.

METHODS

In enucleated porcine eyes a superficial lamellar scleral flap of 5 x 5 mm was surgically dissected. The deep lamella was removed using a pulsed erbium:YAG, a CO2 or an excimer laser (10 eyes/group). All eyes were analysed histologically and 3 in each group by scanning electron microscopy (SEM).

RESULTS

It is feasible to ablate the deep corneoscleral lamella with the CO2, excimer and erbium:YAG lasers without perforating the anterior chamber. The following histology and SEM showed a smoother surface after dissection with the CO2 and excimer lasers compared to the erbium:YAG laser. There was no thermal damage after excimer laser treatment, compared to a damage zone of 10-30 mum using the erbium laser and one of 70-100 microm with the CO2 laser.

CONCLUSIONS

Excimer,erbium:YAG and CO2 lasers allow the microsurgical dissection of the deep lamella. The excimer and CO2 lasers achieve a more regular and smoother tissue surface. The excimer laser has the advantage to dissect without thermal tissue damage.

Long-term results of Erbium YAG-laser-assisted deep sclerectomy

PURPOSE

To evaluate the long-term results of Erbium YAG-laser-assisted deep sclerectomy (DS). In this procedure, the delicate dissection of a deep corneoscleral lamella is greatly simplified by using the Erbium YAG-laser.

METHODS

Data of 14 consecutive patients (10 male, four female, age 67.7+/-10.4 years), who underwent surgery from 1999 to 2000 were analysed retrospectively. The procedure was begun as a standard DS. The deep corneoscleral lamella was dissected with a pulsed Erbium YAG-laser (energy: 40-100 mJ, frequency: 5-10 Hz). Schlemm's canal was unroofed and the lamella thinned until aqueous percolated continuously through the membrane.

RESULTS

The mean follow-up time was 50.4+/-6.8 months. The mean preoperative intraocular pressure (IOP) was 37.7+/-10.5 mmHg. The mean postoperative IOP was 16.1+/-3.9 mmHg at 1 month, 15.1+/-4.3 mmHg at 3 months, 16.4+/-4.5 mmHg at 12 months, and 17.6+/-8.7 mmHg at 50.5 months. The complete success rates (IOP< or =21 mmHg+IOP reduction > or =20% without glaucoma medication) were 83.3% at 3 months and 50% at 12 and 50.5 months. Rates for qualified success (IOP< or =21 mmHg+IOP reduction > or =20% with glaucoma medication) were 91.7% at 3 months, 92.9% at 12 months, and 78.6% at 50.5 months. The number of glaucoma medications was reduced from 3.07+/-0.92 preoperatively to 1.14+/-1.41 at 50.5 months. A single case of anterior-chamber penetration, requiring iridectomy, was the only intraoperative complication.

CONCLUSIONS

Erbium YAG-laser-assisted DS has the advantage of a greatly simplified dissection, while offering a successful long-term IOP control comparable to conventional DS.

Experimental studies on nonpenetrating filtration surgery using the CO2 laser

BACKGROUND

This study evaluated the use of a CO2 laser for performing deep sclerectomy in nonpenetrating filtration surgery.

METHODS

Three experimental models were performed: enucleated sheep and cow eyes (n=18) to determine optimal irradiation parameters, live rabbit eyes (n=20) to test feasibility, and cadaver eyes (40 procedures in 20 eyes) to study effects in human eyes tissue. After a half-thickness scleral flap was created, deep sclerectomy was performed by CO2 laser applications on the scleral bed down to the trabeculo-Descemet's membrane.

RESULTS

Fluid percolation was repeatedly achieved without penetration in sheep and cow eyes using scanned laser energy of 5-10 W at a pulse duration of 200 micros and a working distance of 35 cm. In live rabbits, deep sclerectomy was achieved without perforation in 19/20 eyes. Intraocular pressure was significantly decreased on the first postoperative day (10.3+/-5.1 mmHg lower, on average, than in the nonoperated fellow eye; P<0.001), and this persisted for 21 days. Operations on all cadaver eyes resulted in effective fluid percolation. Penetration of the scleral wall occurred in five cases only after repeated laser applications with high energy. Histologically, a thin sclerocorneal intact wall was demonstrated at the sclerectomy bed. Collateral tissue damage did not extend beyond 100 microm, and adjacent structures remained unharmed.

CONCLUSIONS

CO2 laser-assisted deep sclerectomy is a feasible and apparently safe procedure.