Rationale: Diplopia due to ocular motility disturbance is a common complication after glaucoma drainage device (GDD) surgery. The treatment options include prescription prism glasses, strabismus surgery or GDD removal. However, to the best of our knowledge, GDD size reduction surgery has not been reported.
Patient concerns and diagnoses: An 83-year-old woman diagnosed with primary open angle glaucoma was referred to Tsukazaki Hospital due to uncontrolled intraocular pressure (IOP) in December 2015. We performed an EXPRESS shunt surgery on both eyes in January 2016 and a needling procedure on the left eye in May 2017. Thereafter, because IOP in her left eye remained high, we performed Baerveldt 350-mm implantation in her inferotemporal area by placing the tube at the sulcus on December 3, 2017. The next day, 4Δ hypertropia (HT) was detected in the left eye in alternate cover testing in primary gaze, and diplopia in the inferotemporal direction was demonstrated. Although IOP was controlled well between 15 and 20 mmHg in her left eye, diplopia did not improve.
Interventions: Three weeks later, we performed a plate size reduction surgery for the Baerveldt 350-mm implant. In this procedure, we cut and removed the plates placed beneath the lateral rectus muscle and inferior rectus muscle, which were thought to be responsible for diplopia.
Outcomes: Diplopia improved subjectively, but there was no drastic objective change. We prescribed prism glasses (3Δ base down for the left eye) for remaining mild diplopia. On January 21, 2019, significant objective improvement (2Δ HT with less ocular motor dysfunction demonstrated in the Hess chart) was finally observed.
Lessons: Early plate size reduction surgery, which was not immediately but ultimately effective in improving motor disturbance in our case, could be a potential option to relieve operation-induced motor disturbance. However, notably, tube shunt surgery has the risk of motility disturbances, which might require additional treatment.