Optic perineuritis is a rare syndrome characterized by bilateral, sometimes unilateral, optic disc swelling without a raised cerebrospinal fluid (CSF) pressure and visual dysfunction except for big blind spots, which are presumed to be an inflammation of the optic nerve sheaths. Syphilitic infection is known to be most commonly associated with optic perineuritis. We present three cases of optic perineuritis without syphilitic infection. Two of them showed disc swelling and blind spot enlargement bilaterally, which subsided in a good response to the corticosteroid therapy. In the remaining one case, the left eye exhibited disc swelling without visual disturbance as in the other cases, while anterior ischemic optic neuropathy occurred and produced the permanent visual field defect in the right eye, presumably due to the coincidental existence of optic disc hypoplasia. CSF in all cases showed normal pressure and lymphocytosis, which faded in response to the corticosteroid therapy. A lumbar puncture was a critical maneuver for the correct diagnosis. Despite the overall favorable outcome, immediate treatment should be considered for optic perineuritis patients, especially those who have a local anatomical vulnerability of the disc.