The effects of vertical rectus muscle surgery on the anterior segment and iris fluorescein angiogram were documented in 43 eyes of 41 adult patients. Characteristic iris sector perfusion defects were seen in 33 of 37 eyes (89%) after primary vertical rectus muscle surgery (no previous surgery on these muscles). Although iris perfusion defects were commonly present, associated clinical signs were mild. Two patients developed permanent pupillary changes after simultaneous surgery on two rectus muscles (superior/inferior rectus muscles and contiguous inferior/medial rectus muscles). In most patients, clinical findings resolved and the iris circulation recovered during the first 2 weeks after surgery. In 3 of 8 patients with grade 3 anterior segment ischemia (pupil dysfunction and cells) or early "postoperative uveitis," recovery of iris circulation took up to 12 weeks. These findings indicate that the time course of recovery of the anterior segment circulation after vertical rectus muscle surgery may be shorter than previously assumed.