A laser surgery used to lower intraocular pressure by curtailing aqueous production may be doing more harm than good, according to a new report. A Florida-based research team found significant vision loss—defined as more than two lines of acuity—occurred in 33% of patients who received the procedure. The retrospective review looked at 33 patients who underwent diode laser transscleral cyclophotocoagulation (TSCPC) for uncontrolled intraocular pressure (IOP) from 2014 to 2016.

The study supports previous demonstrations of TSCPC’s efficacy as its 48.3% reduction in IOP from baseline—after a mean follow-up of 12.6 months—is in concordance with previous reports that determined it delivers IOP reductions of 12.3% to 66% from baseline. However, “even with proven efficacy, it is the vision-threatening complications that deter the widespread use of TSCPC in patients with good vision,” the report reads.

It’s unclear why some patients experience vision loss and others don’t. Of the 11 who did, two had IOL subluxation in the setting of pseudoexfoliative glaucoma. One patient did develop vision loss as a consequence of cystoid macular edema and two had corneal pathology before TSCPC, and the authors suspect the laser procedure may have exacerbated the development of corneal edema in those patients. Another had complications with a glaucoma drainage device.

Other common complications included postoperative iritis (56.3%) and cystoid macular edema (12.5%).