To investigate the visual sensations experienced by patients during vitrectomy under retrobulbar anesthesia. Cross-sectional study. Fifty-six men and 45 women with a mean age of 62.2 +/- 11.9 years (range, 30 to 89 years) were studied. Twenty-two eyes had an idiopathic epiretinal membrane, 10 had an idiopathic macular hole, 29 had macular edema (16 resulting from diabetic retinopathy and 13 resulting from retinal vein occlusion), 14 had proliferative diabetic retinopathy, 13 had rhegmatogenous retinal detachment, four had proliferative vitreoretinopathy, and nine had other retinal diseases. The patients were questioned about their visual sensations during and within three hours after vitrectomy, which was performed under retrobulbar anesthesia using 2% lidocaine hydrochloride. Visual sensations perceived by the patients during surgery were reviewed. Ninety-one of the 101 patients experienced some type of visual sensation during the vitrectomy. Ninety-one (90.1%) patients reported seeing lights, 73 (72.3%) patients reported seeing one or more colors, and 57 (56.4%) patients reported seeing movements or moving objects. Of these latter 57 patients, 54 saw instruments and nine (8.9%) saw the surgeon's fingers or hands. In the 94 cases that had triamcinolone-assisted vitrectomy, 35 (37.2%) reported seeing many diffuse whirling black spots. Six patients (5.9%) found the visual experiences frightening. Visual sensations are experienced by approximately 90% of the patients despite full pain control, and surgeons should warn patients of these possibilities because they can be frightening. This should minimize patients' anxiety and stress during the surgery.