Incidence and Clinical Characteristics of Postoperative Endophthalmitis After Ab-Interno Canaloplasty

Asher Khan,1,2 Kamran M Riaz,2 Neal Rangu,1,2 Vinay A Shah,2 Zain S Hussain,2,3 Mahmoud A Khaimi2 1College of Medicine, University of Oklahoma, Oklahoma City, OK, USA; 2Dean McGee Eye Institute, University of Oklahoma, Oklahoma City, OK, USA; 3University of Medicine and Health Sciences, Basseterre, Saint Kitts and NevisCorrespondence: Kamran M Riaz, Dean McGee Eye Institute, University of Oklahoma, 608 Stanton L. Young Blvd, Oklahoma City, OK, 73104, USA, Tel +1 405-271-1095, Fax +1 405-271-3680, Email Kamran-Riaz@dmei.orgIntroduction: Postoperative endophthalmitis (POE) is a rare but devastating complication of ophthalmic surgeries. Microinvasive glaucoma surgery (MIGS) procedures have become increasingly utilized for the surgical reduction of intraocular pressure (IOP). Ab-interno canaloplasty (ABiC) is a popular MIGS procedure, but POE rates and clinical effects following ABiC have not been studied.Methods: This study conducted a retrospective review of all consecutive cases of either standalone ABiC or combined ABiC with phacoemulsification performed at a tertiary care academic referral center from 2015 to 2021. Exclusion criteria included a history of incisional glaucoma surgery, retinal surgery, or additional concurrent microinvasive glaucoma surgery (MIGS) at the time of ABiC. The rates of POE after ABiC were calculated with 95% confidence intervals (CI) based on the Clopper-Pearson exact method.Results: Of 3256 cases of ABiC, one case (0.03%, 1/3256, 95% CI: 0.00– 0.17%) of post-ABiC endophthalmitis was identified. The rate of POE in standalone ABiC was 0.00% (0/1332 cases, 95% CI: 0.00– 0.28%), whereas the rate in combined ABiC with phacoemulsification was 0.05% (1/1924 cases, 95% CI: 0.00– 0.29%). Additionally, the rate of POE following stand-alone cataract surgery, 0.10%, 11/11,470 cases, 95% CI: 0.05– 0.17%), total cataract surgeries, 0.06% (17/28,013 cases, 95% CI: 0.04– 0.10%), total MIGs, excluding ABiC, surgeries, 0.08%, (3/3845 cases, 95% CI: 0.02– 0.23%) portray non-inferiority of ABiC in the risk of POE. The case of ABiC-POE presented four days after surgery and required a vitreous tap with intraocular injection of antibiotics and pars plana vitrectomy. No causative organism was identified. A final 1-year follow-up revealed a corrected distance visual acuity of 20/40 and stable glaucoma.Conclusion: The rate of POE after ABiC (1 per 3256 cases) is statistically non-inferior to the reported incidence of POE after other MIGS and incisional glaucoma surgeries.Keywords: ab-interno canaloplasty, canaloplasty, endophthalmitis, post-operative infections