Because the LiGHT trial demonstrated selective laser trabeculoplasty’s (SLT) strong potential for treating patients with newly diagnosed ocular hypertension and primary open-angle glaucoma, researchers have begun investigating SLT’s potential in other forms of glaucoma. A recent study used anterior segment OCT (AS-OCT) to evaluate the presence of angle dysgenesis in juvenile-onset primary open-angle glaucoma (JOAG) as a predictive factor of SLT’s efficacy and reported that the presence of Schlemm’s canal on AS-OCT was a strong predictor for IOP reduction in these eyes.
The prospective clinical cohort study included 46 JOAG patients with uncontrolled IOP (>22mm Hg in both eyes) who were scheduled to undergo SLT. The researchers evaluated the presence of angle dysgenesis on AS-OCT, which was defined as “the absence of Schlemm’s canal and/or presence of hyperreflective membrane over trabecular meshwork as identified on AS-OCT before the SLT procedure.” They defined SLT success as an IOP reduction of 20% or more at six months, without additional IOP-lowering medications or surgery (though repeat SLT performed within the six months counted as success).
The researchers reported that 57.1% of eyes demonstrated an IOP reduction of at least 20% at six months (mean reduction 7.6mm Hg). Schlemm’s canal was found in significantly more eyes that experienced success (80%) than failure (26.6%). Other findings included:
- All eyes with hyperreflective membrane showed failure (n=5).
- All eyes with Schlemm’s canal present in more than 50% of AS-OCT B-scans showed success (n=19).
The researchers noted that “on a bias-reduced regression analysis, the identification of Schlemm’s canal on any two consecutive scans increased the chances of success at six months by 8.3 times, while the identification of Schlemm’s canal in more than 50% of AS-OCT scans was associated with a 21.4-times greater chance of success.”
An earlier study conducted by these same researchers reported that JOAG patients had a 40% success rate with SLT as a primary treatment. “We had found angle dysgenesis as seen on goniophotographs to be a predictor for failure of SLT,” they noted. “Angle dysgenesis, however, may not always be seen on gonioscopy, as it has been known to be present in histopathological samples of trabecular meshwork from eyes with gonioscopically normal-appearing angles. With the advent of HD OCT, the angle can be visualized at higher resolution to look for the presence or absence of Schlemm’s canal or abnormal tissue at the angle.”
“We believe that visualization of Schlemm’s canal on AS-OCT before performing SLT may help deliver an expected outcome-based individualized treatment plan for patients,” the researchers concluded. “The centers that possess spectral domain OCT could use it in prognosticating the outcomes.”
“Moreover,” they added, “imaging the angle for trabecular meshwork and Schlemm’s canal may help in selecting potential candidates for SLT and providing more realistic expectations when advising patients, regarding the likelihood of success/failure of their SLT treatment.”
Varshney T, Azmira K, Gupta S, et al. In vivo imaging of the Schlemm’s canal and the response to selective laser trabeculoplasty. Am J Ophthalmol. 2021. [Epub ahead of print].