Prospective study of ab externo erbium:YAG laser sclerostomy in humans

Er:YAG laser-assisted filtration surgery: initial results in rabbits

Background

Glaucoma is a leading cause of global blindness, especially preventable blindness. The increased prevalence of glaucoma has led to a growing demand for newer, safer, more rapid, and simpler treatments for the reduction of intraocular pressure (IOP). In this study, we evaluated the safety and feasibility of performing filtration glaucoma surgery with an Ab-Interno Er:YAG laser in rabbits.

Methods

Nine New Zealand White rabbits age 16weeks were studied. After subconjunctival injection of mitomycin C (MMC), a novel Ab-Interno Er:YAG laser probe was inserted into the anterior chamber (AC) through a clear corneal 1mm paracentesis and directed at the trabecular meshwork adjacent to the MMC injection area. A pulsed laser beam was applied to create a patent sclerostomy connecting the AC to the subconjuctival space, resulting in a filtering bleb. The laser system used was the Er:YAG laser system - LAS25-FCU, (Pantec Biosolutions AG, Liechtenstein). Parameters used: Wave lengh: 2940nm, Pulse length: 100400sec,frequency: 250Hz. Average laser power in accordance to the fiber tip diameter: 0.85W(range 0.80.92W). Complete ocular exams, including IOP measurements, were performed on 1, 7, 14, and 23days postoperatively. Three rabbits were sacrificed on days 1, 14, and 23, and histological examinations were performed on all nine eyes.

Results

All procedures resulted in a functional medium-large superior bleb without significant complications. The bleb was sustained in all rabbits by day 14 and in one of the three rabbits that reached the last follow-up at 23days. No cases of postoperative hypotony were observed. There was a transient significant reduction in mean IOP on postoperative days 5 and 7 (P=0.028). Histopathological analysis revealed a patent full-thickness scleral tunnel with only a minor degree of surrounding coagulation necrosis.

Conclusions

The Ab-Interno laser sclerostomy procedure is potentially safe and effective based on initial experience in an in-vivo rabbit animal model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01986-4.

Laser treatment of periocular skin conditions

Advances in laser technology in recent decades have increased the options for the treatment of dermatologic conditions of the eye and eyelid. Benign tumors can be laser-ablated with relative ease, and vascular and melanocytic lesions can be precisely targeted with modern lasers. In this contribution, we review treatment of periocular pigmented lesions, including melanocytic nevi and nevus of Ota; vascular lesions including telangiectasias, port wine stains, and infantile hemangiomas; hair removal; eyeliner tattoo removal; laser ablation of common benign periocular tumors, such as syringomas, xanthelasma, milia, and seborrheic keratoses; and laser resurfacing. The recent advent of fractionated laser technology has resulted in dramatically decreased healing times for periocular skin resurfacing and fewer adverse effects. Fractionated laser resurfacing has now nearly supplanted traditional full-field laser resurfacing, and safe treatment of rhytides on the thin skin of the eyelids is possible. Proper eye protection is, of course, essential when using lasers near the eye. Patient preparation, safety precautions, and risks--intraocular and extraocular--are discussed herein. As laser technology continues to advance, we are sure to see improvements in current treatments, as well as development of new applications of cutaneous lasers.

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.

Erbium: YAG laser trabecular ablation (LTA) in the surgical treatment of glaucoma

BACKGROUND AND OBJECTIVE

Laser trabecular ablation (LTA) aims to remove trabecular tissue and to open Schlemm's canal in order to improve outflow facility in glaucomatous eyes. The purpose of our study was to investigate the pressure-reducing effect of LTA in chronic open-angle glaucoma 1 year following laser surgery.

STUDY DESIGN/MATERIALS AND METHODS

Eleven eyes of 11 patients with chronic open-angle glaucoma were treated by circumscribed laser ablation of the trabecular meshwork. We used an Erbium:YAG laser (2.94 microm) with a quartz fiber contact endoprobe (320 microm core-diameter, 385 microm coating-diameter) applying 11-30 single neighbouring laser pulses (5-7 mJ) to the trabecular meshwork by an ab-interno approach. Laser procedure was gonioscopically visualized.

RESULTS

Mean maximum intraocular pressure (IOP) of all 11 patients before LTA was 36 mmHg and dropped down to 22 mmHg after a mean follow-up of 12 months following LTA; this represents an IOP decrease of 38% (P=0.008). The average number of medications per eye dropped from 2.8 to 1.5 per eye (P=0.021).

CONCLUSION

Although IOP lowering effect of Erbium:YAG laser trabecular ablation did not prove as effective as in filtering procedures, LTA might be a valuable alternative in glaucoma surgery especially in order to avoid conjunctival scarring and postoperative hypotony.