Optic nerve sheath fenestration was performed in 26 eyes for treatment of the progressive type of common (nonarteritic) anterior ischemic optic neuropathy. During a mean follow-up period of 21 weeks (range, 6 to 52 weeks), results were as follows: visual acuity increased by two or more lines on the Snellen chart in 7 eyes; visual acuity decreased by two or more lines in four eyes; some regression of visual field defects occurred in six eyes, including two eyes in which acuity also improved. These results, attributed to surgical decompression, do not exceed the spontaneous recovery rates reported in the literature pertaining to nonarteritic anterior ischemic optic neuropathy and fail to substantiate the sanguine visual outcome in recently reported series of patients undergoing optic nerve sheath decompression.