Study: Using pilocarpine drops post goniotomy may reduce long-term glaucoma medication needs

Using pilocarpine eye drops following Kahook Dual Blade (KDB) goniotomy surgery may improve clinical outcomes for patients with glaucoma and reduce the need for future medications, according to new research published by faculty members and trainees in the Department of Ophthalmology at the University of Colorado School of Medicine.

“The KDB goniotomy is a minimally invasive glaucoma surgery that we do a lot here at the Sue Anschutz-Rodgers Eye Center, and there was some variability in the post-operative eye drop regimen among different providers,” says Julia Xia, MD, a uveitis fellow in the department and lead author of the study.

“Some of our providers prescribe pilocarpine drops and some do not,” she continues. “There currently is not a clear evidence-based consensus on whether the drops are beneficial in use after the surgery, so this research sought to address whether those drops made a difference.”

The study analyzed 532 KDB goniotomy procedures at the Sue Anschutz-Rodgers Eye Center between September 2015 and March 2020, with and without pilocarpine use, and measured surgical success, which the researchers defined as intraocular pressure less than 21 mmHg in addition to either a more than 20% reduction in intraocular pressure or the reduction of one or more topical glaucoma medications.

The group using pilocarpine drops had a significantly higher success rate in the first and third month after surgery as well as one year after surgery. They also required significantly less medications than the group that did not use pilocarpine.

The role of pilocarpine drops

Researchers estimate that more than 4.2 million adults in the U.S. have glaucoma, an eye disease that gradually damages the optic nerve when there’s a build-up of fluid. There is no cure for glaucoma, so ophthalmologists are tasked with helping their patients manage the disease and the excessive intraocular pressure (IOP) that leads to vision problems.

Management often includes eye drops and surgeries that aim to reduce IOP. Goniotomy is a minimally invasive surgery that opens the trabecular meshwork, the eye’s drainage system, and allows fluid to flow out of the eye, thus reducing pressure.

“If you think of the eye as a sink, we are essentially trying to augment the drain,” Xia says. “We’re making an incision to open up the natural drainage pathway.”

There are several ways ophthalmologists can perform a goniotomy, but researchers of the study focused their efforts on the Kahook Dual Blade method, which was developed by Malik Y. Kahook, MD, professor of ophthalmology and the Slater Family Endowed Chair in Ophthalmology, over a decade ago on the CU Anschutz Medical Campus.

“Pilocarpine historically has been used to lower eye pressure, but it also shrinks the pupil and creates tension in key areas of the drainage pathway,” Xia explains. “This theoretically helps ensure that the pathway remains open after someone has healed from surgery which allows fluid to better flow out of the eye.”

Patients in the study who used the drops typically did so for about a month following the procedure.

After that, they tended to need fewer glaucoma medications to manage the disease.

Looking to the long term

The findings are an important clinical tool for ophthalmologists who perform KDB goniotomy.

“The exciting part about this research is that it can be directly applicable to patients,” Xia says. “Surgeons can use this evidence as one piece of the decision-making process when thinking about what’s best for their patients.”

While the results from the study are promising, ophthalmologists, including Xia, say pilocarpine drops do often come with some nuances. For many patients, side effects include headache, blurred vision, heightened risk for retinal detachment, and temporary burning or stinging in the eye.

Cara Capitena Young, MD, associate professor of ophthalmology and medical director of the Sue Anschutz-Rodgers Eye Center operating room, says there are patients who may not be a good fit for the drops, but the research has convinced her to add pilocarpine drops back into her toolbox and discuss them with her patients.

Capitena-Young also co-authored the study.

“Drop adherence is a massive barrier to treating glaucoma, so if we can add a drop in the short term that helps reduce the number of drops needed long term, it can be a great option for some patients,” she says. “We know from this research that it can extend the success of the surgery well beyond a year, so while the drops might be an additional annoyance for a little bit, it can be worth it.”