Mechanism of visual sensations experienced during pars plana vitrectomy under retrobulbar anesthesia

Purpose: To investigate the visual sensations experienced by patients during vitrectomy under retrobulbar anesthesia. Methods: 30 men and 45 women with a mean age of 65.3 ± 10.6 years underwent vitrectomy under retrobulbar anesthesia for macular disease. 28 eyes had an idiopathic epiretinal membrane, 13 had an idiopathic macular hole, 32 had macular edema (17 diabetic retinopathy and 15 retinal vein occlusion), and 2 had submacular hemorrhage. 49 patients with nonmacular disease underwent similar vitrectomy procedures and were used for comparison. An interview was conducted with the patient about his/her visual sensations during and within 3 h of the vitrectomy. Results: 70 (93.3%) of the patients reported seeing lights, 53 (70.7%) reported seeing colors, and 48 (64.0%) reported seeing movements or moving objects. Of the patients who reported seeing movements or moving objects, 44 (58.7%) reported seeing surgical instruments, and 5 (6.7%) saw the surgeon's fingers or hands. Patients with macular diseases tended to report more visual sensations than patients with nonmacular diseases. The patients' description and drawings appeared to arise mainly from the shadows cast by the intravitreal objects, and some patients perceived highly accurate details including the movements and color of the objects. Conclusions: Visual sensations are experienced by approximately 90% of the patients, and there may be a common mechanism by which patients perceive the intravitreal objects that are not focused on by the retina through the eye's optical system.