Strabismus/Diplopia After Glaucoma Drainage Devices: A Systematic Review of Method-Dependent Rates, Time Courses, Risk Factors, and Managements

Purpose: To synthesize method-dependent rates, time courses, risk factors, mechanisms, and management of strabismus/diplopia after glaucoma drainage device (GDD) surgery. Methods: PRISMA2020 systematic review (PROSPERO CRD420251110465) across seven databases to 21 July 2025, including randomized trials, cohorts, and case series. Outcomes were prespecified: incidence (early (less than 3 months) and late (more than 12 months), visit prevalence by standardized orthoptics or patient reported outcome measures (PROMs), and chart documented postoperative occurrence. Narrative synthesis followed SWiM guidance. Denominators were per patient for diplopia/strabismus and per eye for motility limitation. Results: Ninety-one studies (11,681 patients from 12,068 eyes) met criteria. Onset clustered early (median 6 weeks), followed by two trajectories, many cases remitted with capsule remodeling; a minority persisted with restrictive tethering. Apparent rates varied by ascertainment and unit: persistent diplopia was 0 until 5% in contemporary chart ascertained cohorts, around 5% at 1 year and around 4% at 5 years in standardized orthoptic trials, and up to around 23% at 1 year in PROM studies. Surgical anatomy and tissue planes outweighed device family or nominal plate size: inferior placement increased early strabismus (around 21% at 3 months vs 0% with superior placement), and pars plana entry showed higher diplopia than anterior chamber entry in matched cohorts. Mechanism was predominantly restrictive (posterior fixation-like) from capsule-muscle coupling. Management mirrored the natural history: early symptoms often resolved with observation/prisms; persistent, clearly restrictive deviations benefited from capsule aware adhesiolysis with limited, targeted rectus surgery; device revision/explant was uncommon. Conclusion: Post GDD motility morbidity is chiefly restrictive and measurement dependent. Reports should separate incidence from visit prevalence, distinguish any from persistent diplopia, and use per patient denominators for diplopia/strabismus and per eye for motility limitation. Future trials should standardize orthoptic endpoints, pair PROMs with imaging of the plate-muscle interface, and power for motility outcomes alongside IOP.