Laser trabeculoplasty (LTP) is known as a safe and effective glaucoma therapy, but the factors that influence response duration are unknown. In a new retrospective cohort study, researchers pulled data from 79,332 eyes in the Academy of Ophthalmology’s IRIS registry that had an LTP procedure and diagnosis of glaucoma.

In responders with greater than 20% IOP reduction, any post-LTP IOP that was above 80% of baseline was considered a failure. Eyes were excluded if IOP-lowering medication or procedures were added or performed, or if the eye reached the end of follow-up.

The findings showed eyes with a higher baseline IOP had longer survival—84.2% at one year and 59.2% at two years, and 0.2% failure at six months, 6.1 % failure at 12 months and 40.8% failure at 24 months. These were better results than previously studies which ranged between 25% to 33% failure by six months and 47% to 73% failure by 24 months. The authors noted this may be due either the IRIS Registry cohort being older and/or their study defining a technical failure event separate from “treatment failure.”

Uveitis and angle recession significantly increased the risk of reaching failure events, while eyes with high baseline IOP (greater than 24mm Hg) had the longest survival compared to eyes with lower baseline IOP. Eyes not receiving glaucoma medications at the time of LTP treatment remained medication-free for a median of 197 days.

The analysis of angle recession and uveitis failures following LTP treatment may imply different mechanisms of trabecular dysfunction in these diseases, the authors noted in their study.

“At six months post-LTP, a larger proportion of angle recession eyes had failed compared to uveitic eyes,” the authors explained in their study. “However, by 18 months, the proportion of failures in both groups were comparable (47.5% angle recession vs 48.3% uveitic).” The earlier failure in the first group may be attributed to the different ways the trabecular tissues are affected in angle recession (irreversible metaplasia) vs. uveitis (partially reversible trabecular dysfunction), they speculate. “Furthermore, as IOP fluctuations may be associated with uveitis flareup, the LTP failure rates may vary greatly in different types of uveitis.” The authors caution that their results may not be easily generalizable to the public at large, given the small proportion of eyes with either angle recession or uveitis in their cohort.

Overall, the authors concluded that offering LTP to alleviate burden in glaucoma patients is effective, but “future studies that analyze LTP practice patterns and implementation lag would facilitate resource optimization in glaucoma therapy.”

Chang TC, Vanner EA, Fujino D, et al. Factors associated with laser trabeculoplasty response and duration: analysis of a large clinical database (IRIS Registry). Journal of Glaucoma. [Epub ahead of print].