Prolonged preoperative use of glaucoma eye drops linked to risk for trabeculectomy failure
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Key takeaways:
- A lower Glaucoma Medication Intensity Index (GMII) was tied to longer surgical success duration.
- Older age at surgery, higher GMII and subsequent cataract surgeries were risk factors for surgical failure.
Extended preoperative use of topical glaucoma medications with preservatives may negatively affect long-term trabeculectomy outcomes, according to a study published in Scientific Reports.
“Considering that trabeculectomy is typically performed in patients who were already treated with multiple glaucoma medications for extended periods, understanding the effect of long-term preoperative medication use on surgical outcomes is crucial,” Somi Lee, from the department of ophthalmology at Yeungnam University Hospital in Korea, and colleagues wrote.
In a retrospective study of 201 patients (309 eyes) with primary open-angle glaucoma who underwent trabeculectomy between 1999 and 2014, the researchers assessed the association between preoperative topical glaucoma medication with preservatives and long-term outcomes. They calculated a Glaucoma Medication Intensity Index (GMII) to quantify use of these medications and determined cumulative success rates after surgery.
According to study results, cumulative success rates for all patients were 89.3% at 1 year, 70.6% at 5 years, 59.2% at 10 years and 46% at 20 years.
Upon dividing the patients into surgical success and failure groups, based on the last follow-up visit, the researchers found that the GMII was significantly lower in the surgical success group at all timepoints. In addition, the low GMII group, defined as having a GMII less than 4.35, had a longer duration of surgical success and lower IOP at 20 years compared with the high GMII group.
Further, older age at surgery, higher GMII and subsequent cataract surgeries were significantly associated with surgical failure. Age at surgery or glaucoma diagnosis was positively and negatively associated with GMII and cataract surgery, respectively, following trabeculectomy.
“The prolonged preoperative use of glaucoma eye drops is a risk factor for trabeculectomy failure,” Lee and colleagues wrote. “The GMII can clinically quantify the cumulative use of glaucoma medications and help determine the optimal timing of surgery. Further research is needed to understand how long-term use of these medications affects conjunctival changes as well as bleb formation and function after trabeculectomy.”
Perspective
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This study was successful in establishing a method to quantify the amount of glaucoma medications a patient has taken before undergoing a trabeculectomy, which served to better isolate the direct impact of prior medication use on surgical success rates.
The study significantly demonstrates that patients with a higher usage of glaucoma medications had a higher incidence of surgical failure, which suggests that surgical intervention should be considered sooner.
One shortcoming of this study, however, is that it excluded preservative-free glaucoma drops, and because many preservatives are known to contribute to conjunctival inflammation, it cannot yet be definitively determined that prolonged use of glaucoma medications themselves are contributing to surgical failure rather than the preservatives themselves.
It was also shown that surgical failure had a significant correlation with older age at the time of surgery; therefore, it would be prudent for future studies to better control the age of patients at the time of trabeculectomy.
In short, after reviewing this study, practicing ODs can consider referring their glaucoma patients for surgical consultations sooner rather than later, but further studies are needed before significant changes are made to the clinical standard of care.
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