The primary cause of elevated IOP in most cases of openangle glaucoma (OAG) is increased outflow resistance in the juxtacanalicular trabecular meshwork (TM) and inner wall of the canal of Schlemm.1 The goal of performing laser surgery at the anterior chamber angle is to re-establish a physiological aqueous outflow pathway. Experiments with photothermal and photodisruptive lasers (ruby, Nd:YAG, and argon) were compromised by scarring through inflammatory and healing responses.2-11 Excimer laser trabeculostomy (in Europe, “trabeculotomy”; ELT) uses a nonthermal, short-pulsed, 308-nm, xenon-chloride excimer laser to ablate the TM. The pores created have sharp edges, thus avoiding scar formation.12-15

PROCEDURE

ELT can be performed as a standalone procedure or in combination with cataract surgery (phacoemulsification plus ELT). Local anesthesia is adequate. Visualization of the TM is achieved by gonioscopy or via an endoscope. A fiber optic probe enters the anterior chamber through a paracentesis, and with the probe in direct contact with the TM, the pulsed laser energy is applied.16 In the current protocol, five to 10 pores are created over 90º of the TM (Figure). Slight retrograde bleeding from the canal of Schlemm is not considered a complication but indicates patency of the created pores. The decrease in IOP is usually present from the first day after the procedure and remains stable over time. The ELT procedure takes less than 5 minutes.17

RESULTS

The first human clinical trial of ELT was performed in Germany in 1997. In 22 eyes with OAG, the median reduction in IOP was 7 mm Hg.18 There was only minimal trauma to the eye. Of particular note, there is no conjunctival manipulation to compromise later filtering surgery.

Since 1997, numerous clinical studies have demonstrated ELT's ability safely to achieve a long-term reduction in IOP. A retrospective study assessed 70 eyes after ELT and 60 eyes after combined phacoemulsification plus ELT that had a diagnosis of primary OAG or ocular hypertension.

The study had a follow-up period of up to 26 months. The investigators reported a reduction of IOP in the ELT group from 24.1 ±0.7 mm Hg to 18.8 ±0.8 mm Hg after 1 year and to 16.8 ±1 mm Hg after 2 years (-30.3%), while the number of antiglaucoma drugs decreased slightly (1.9 ±0.1 dropping to 1.5 ±0.3 after 2 years). In the combined group, the IOP decreased from 22.4 ±0.6 mm Hg to 16.4 ±0.4 mm Hg at 1 year and 12.8 ±1.5 mm Hg after 2 years (-42.9%), while the number of antiglaucoma drugs remained almost constant (from 1.1 ±0.2 to 1.2 ±0.2 after 2 years).17

A recently published study exclusively analyzed combined phacoemulsification plus ELT (n = 24) and confirmed an immediate pressure-lowering effect. This study also confirmed a significant decrease in medication after a follow-up period of 1 year (25.5 ±2.9 mm Hg dropping to 16.5 ±5 mm Hg, -35.3%; antiglaucoma drugs, 2.3 ±1.3 dropping to 1.5 ±1.4, -34.8%).19

CONCLUSION

ELT is a promising, minimally invasive treatment for lowering IOP in eyes with OAG. It has been approved for use in the European Union and Switzerland for more than a decade. Currently, clinical studies and FDA approval are pending in the United States and Canada.

Michael S. Berlin, MD, MS, the director of the Glaucoma Institute of Beverly Hills, is also a professor of clinical ophthalmology at the Jules Stein Eye Institute, University of California, Los Angeles. As the inventor of ELT, he holds patents for the procedure in the United States and currently has patents issued and pending for next-generation ELT improvements in the United States, Canada, and the European Union.

Dr. Berlin may be reached at (310) 855-1112; berlin@ucla.edu. Ulrich F. Giers, MD, is director of the Eye Hospital, Detmold, Germany.

Lea Kleineberg, MD, is an ophthalmologist at the Eye Hospital, Detmold, Germany.

Richard P. Stodtmeister, MD, is a professor of ophthalmology at the University of Dresden, Germany.

Marc Töteberg-Harms, MD, is a clinical and basic research fellow with the Glaucoma Department at the Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. Dr. Töteberg-Harms acknowledged no financial interest in the material presented herein. He received personal funding by the Swiss National Science Foundation (SNSF Project No. PBZHP3_141457). Dr. Töteberg-Harms may be reached at marc_toeteberg@meei.harvard.edu.

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