Purpose: To report the prevalence, type, and cause of diplopia in medically and surgically treated patients with glaucoma. Design: Cohort study. Participants: A total of 195 adult patients with glaucoma treated in a glaucoma referral practice. Methods: A total of 195 adult patients with glaucoma who had undergone surgical or medical management were prospectively enrolled. Forty-seven patients had undergone glaucoma drainage device (GDD) surgery (Baerveldt 350, Baerveldt 250 [Abbott Medical Optics, Abbott Park, IL], or Ahmed FP7 [New World Medical Inc, Rancho Cucamonga, CA]), 61 patients had undergone trabeculectomy, and 87 patients were medically treated. All patients completed the Diplopia Questionnaire to assess diplopia. We defined the presence of diplopia as "sometimes," "often," or "always" in distance straight ahead or reading positions on the Diplopia Questionnaire. A chart review was performed jointly by a strabismus specialist and a glaucoma subspecialist to characterize the type and cause of the diplopia. Main Outcome Measures: Frequency, type, and cause of diplopia. Results: Diplopia was reported in 41 of 195 medically and surgically treated patients (21%) with glaucoma. Binocular diplopia due to the glaucoma procedure was present in 11 of 47 patients (23%) after GDD (95% confidence interval, 12-38), which was significantly greater than in patients after trabeculectomy (2/61 [3%]; 95% confidence interval, 0.4-11; . P = 0.002). The most common type of strabismus associated with binocular diplopia due to glaucoma surgery was hypertropia (10/11 GDD cases, 2/2 trabeculectomy cases). Monocular diplopia was found in a similar proportion of medically treated, post-trabeculectomy, and post-GDD cases (4/87 [5%], 4/61 [7%], and 2/47 [4%], respectively). Binocular diplopia not due to surgery was found in similar proportions of GDD, trabeculectomy, and medically treated cases (3/47 [6%], 5/61 [8%], and 10/87 [11%], respectively). Conclusions: Diplopia may be under-recognized in medically and surgically treated patients with glaucoma, and standardization of ascertaining patient symptoms using the Diplopia Questionnaire may be useful in these patients. Diplopia was more commonly seen after GDD than trabeculectomy, typically a noncomitant restrictive hypertropia. The prevalence of monocular diplopia and binocular diplopia unrelated to glaucoma surgery was similar among medical and surgical groups. It is important to counsel patients on the higher occurrence of diplopia associated with GDD surgery.
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