Optimizing Surgical Technique

Optimal Performance of Selective Laser Trabeculoplasty

Dahlgren T, Ayala M, Zetterberg M¹
Industry support: None

ABSTRACT SUMMARY

This prospective, multicenter, masked, randomized controlled trial compared the IOP reduction and the time to glaucoma treatment escalation with four different selective laser trabeculoplasty (SLT) treatment protocols. Investigators assessed 400 patients (513 eyes) who had primary open-angle glaucoma, pseudoexfoliative glaucoma, or ocular hypertension. Individuals who had previously undergone laser treatment and/or were currently receiving glaucoma medical therapy were allowed. Those who had a history of glaucoma surgery, a highly pigmented trabecular meshwork, intraocular inflammatory disease within the previous year, or a change in glaucoma medication within the previous 3 months were excluded.

All patients were pretreated with 4% pilocarpine. SLT was performed with a Tango Laser (Lumibird Medical) using the Ocular Latina SLT lens (Ocular Instruments) and a coupling gel. The diameter of the laser spots was 400 µm, the duration was 3 nanoseconds, and the wavelength was 532 nm. The four SLT treatment protocols were as follows: 180º with standard energy, 180º with high energy, 360º with standard energy, and 360º with high energy. Standard energy was defined as laser power titrated to just below the appearance of cavitation bubbles. High energy was defined as the appearance of cavitation bubbles at 50% to 75% of the treatment spots, with a maximum power of 1.4 mJ. For the 180º and 360º treatments, 50 ±5 and 100 ±10 laser spots were used, respectively.

The 360º high-energy protocol achieved the greatest IOP reduction on average at 1 and 6 months, with an average reduction of 5.4 mm Hg (P < .001). This protocol also resulted in the highest number of patients with a 20% IOP reduction after SLT alone at 6 months. In addition, the median time to glaucoma treatment augmentation was more than twice as long with the 360º high-energy protocol (1,323 days; P < .001). Adverse effects were rare in all groups, but the most severe (central retinal vein occlusion) occurred in the 360º high-energy group.

DISCUSSION

How do the results of this trial compare with those of earlier studies?

The study by Dahlgren and colleagues was adequately powered to analyze four treatment protocols. The 360º high-energy treatment protocol was found to be superior, and the difference was clinically significant. Previous reviews showed no significant effects of energy on IOP reduction, and smaller studies found that 360º treatment might be more efficacious than 180º.^2,3

How could the study findings assist clinicians?

A variety of protocols are used for SLT, a long-standing treatment for glaucoma and ocular hypertension. Many physicians employ protocols they learned from colleagues or developed in clinical practice.⁴ The study by Dahlgren and colleagues¹ could guide ophthalmologists on the development of a treatment protocol that best fits their patient population.

Interim Analysis of Clinical Outcomes With Open Versus Closed Conjunctival Implantation of the Xen45 Gel Stent

McGlumphy EJ, Do A, Du A, et al⁵
Industry support: Partially funded by AbbVie

ABSTRACT SUMMARY

This multicenter retrospective study compared open and closed conjunctiva techniques for the implantation of a Xen 45 Gel Stent (AbbVie). Mitomycin C was injected subconjunctivally in all cases.

With the ab interno closed conjunctiva technique, the stent was injected through a clear corneal incision into the superonasal angle until the device exited the sclera 2 mm posterior to the limbus. No primary needling was performed. With the ab externo closed technique, the injector was introduced 7 mm posterior to the limbus, advanced subconjunctivally to 2 mm, and then tunneled into the anterior chamber.

With the ab interno open conjunctiva technique, a 3–clock hour superonasal peritomy was performed, and the injector was introduced through a clear corneal incision. The stent was then injected into the superonasal angle until it exited the sclera 2 mm posterior to the limbus, after which the conjunctiva was closed with a nylon or polyglactin suture. With the ab externo open conjunctiva technique, a 3–clock hour superonasal peritomy was performed, and the injector was placed 2 mm posterior to the limbus and deployed into the anterior chamber. The conjunctiva was closed as previously described.

Patients followed various postoperative steroid and antibiotic regimens depending on the surgeon. Complete success (defined as an IOP < 21 mm Hg or > 20% IOP reduction without medications, with no reoperations, and with no catastrophic events) was achieved in 42.5% and 24.7% of the open and closed groups, respectively (P = .01). Overall success (defined as complete success but with topical medications) was achieved in 64.2% and 37% of the open and closed groups, respectively (P < .001). Bleb needling was performed on 12.4% and 40% of patients in the open and closed groups, respectively. IOP spikes occurred more frequently in the closed versus the open group (40% vs 18%). Adverse events, including suprachoroidal hemorrhage, transient hypotony, implant exposure, and vision loss, were similar between the groups. Choroidal effusion, however, was less likely in the closed group (4.1% vs 13%), and occlusion of the Xen tip by iris tissue was more likely in the closed group (12% vs 1.7%).

DISCUSSION

How do the results of this study compare with earlier findings?

McGlumphy and colleagues provide an excellent update on their earlier research.⁶ Findings from the current study⁵ indicate that the open conjunctiva approach has advantages over the closed conjunctiva approach for the management of patients with severe glaucoma.

Other studies have described the Xen’s overall efficacy in refractory cases.⁷ McGlumphy et al, however, draw a direct comparison between two techniques.⁵

How could the study findings assist clinicians?

The Xen is a relatively new device, and surgical techniques are evolving. The results of this study could help guide surgeons on how to improve their surgical technique.