IMPORTANCE Vitreous floaters are common and can worsen visual quality. YAG vitreolysis is an untested treatment for floaters. OBJECTIVE To evaluate YAG laser vitreolysis vs sham vitreolysis for symptomatic Weiss ring floaters from posterior vitreous detachment. DESIGN, SETTING, AND PARTICIPANTS This single-center, masked, sham-controlled randomized clinical trial was performed from March 25, 2015, to August 3, 2016, in 52 eyes of 52 patients (36 cases and 16 controls) treated at a private ophthalmology practice. INTERVENTIONS Patients were randomly assigned to YAG laser vitreolysis or sham YAG (control). MAIN OUTCOMES AND MEASURES Primary 6-month outcomes were subjective change measured from 0% to 100% using a 10-point visual disturbance score, a 5-level qualitative scale, and National Eye Institute Visual Functioning Questionnaire 25 (NEI VFQ-25). Secondary outcomes included objective change assessed by masked grading of color fundus photography and Early Treatment Diabetic Retinopathy Study best-corrected visual acuity.RESULTS Fifty-two patients (52 eyes; 17 men and 35 women; 51 white and 1 Asian) with symptomatic Weiss rings were enrolled in the study (mean [SD] age, 61.4 [8.0] years for the YAG laser group and 61.1 [6.6] years for the sham group). The YAG laser group reported greater symptomatic improvement (54%) than controls (9%) (difference, 45%; 95% CI, 25%-64%; P < .001). In the YAG laser group, the 10-point visual disturbance score improved by 3.2 vs 0.1 in the sham group (difference, −3.0; 95% CI, −4.3 to −1.7; P < .001). A total of 19 patients (53%) in the YAG laser group reported significantly or completely improved symptoms vs 0 individuals in the sham group (