One Year Outcomes Of An Ab Externo Sibs Microshunt In Combination With Phacoemulsification

Micro-invasive glaucoma surgery provides an additional therapeutic option in the glaucoma treatment algorithm, and may allow for intraocular pressure (IOP) lowering with increased safety. We aim to evaluate the efficacy, risk factors for failure, and safety of an ab-externo SIBS microshunt combined with phacoemulsification after 1 year of follow-up.

Single-center study conducted at an academic ophthalmology center in Toronto, Ontario, Canada.

This was a retrospective, consecutive cohort study of 119 glaucomatous eyes of 97 patients with an IOP above target or progressing on maximal medical therapy. Consecutive eyes underwent ab-externo SIBS microshunt surgery with mitomycin C (MMC) in combination with phacoemulsification from July 2015 to June 2019. The primary outcome was complete success, defined as: 1) no two consecutive IOP readings >17mmHg or IOP <6mmHg with >2 lines of vision loss,  2) at least 20% IOP reduction from baseline and 3) on no medications. Secondary outcomes included upper IOP thresholds of 14mmHg and 21mmHg, qualified success (with medications), change in IOP, medications, visual acuity, complications, interventions, re-operations and risk factors for failure.

Complete success was achieved in 67.5% of eyes and qualified success in 79.8%. For IOP thresholds of 14 and 21mmHg, complete success was achieved in 64.9% and 69.3%, and qualified success was achieved in 77.1% and 81.6%, respectively. At 1 year, median IOP decreased from 22 (IQR 18-27) at baseline to 13 (11-15) (p<0.0005). Medications decreased from 4 (3-4) to 0 (0-0) (p<0.0005), with 75.7% being medication free. Median logMAR BCVA improved from 0.4 (0.2-0.7) to 0.14 (0.1-0.3) (p<0.0001). An MMC dose < 0.4mg/mL (adjusted HR 2.67; 95% CI 1.24-5.75) and left eye (adjusted HR 2.30; 95% CI 1.20-4.41) were statistically significant risk factors for failure. 29 eyes (24.4%) underwent needling and 7 eyes (5.9%) underwent glaucoma reoperation. 

The SIBS microshunt combined with cataract surgery demonstrates promising rates of complete and qualified success, lowered IOP, reduced medication use, significant improvement in visual acuity, and relatively few complications and reoperations at 1 year.  Higher MMC dose may improve efficacy without a significant difference in safety. The efficacy results appear lower than previously reported data on standalone implantation, suggesting that when possible, it may be better to separate the two procedures. Patients should be advised about the higher rates of needling when the microshunt is combined with phacoemulsification. Overall, these results show a promising new procedure that may be added to a glaucoma surgeon’s armamentarium.