A 57-year-old woman had a history of DM for 10 years with infrequent medical checkups. In May 2006, she was hospitalized for amputation of the first to fourth toes in her left foot, which were damaged by gangrene. During the hospitalization, she received intensive insulin therapy, which reduced her glycated hemoglobin level from 13.0% to 5.4% (to convert to a proportion of total hemoglobin, multiply by 0.01) within 2 months, and in June she reported blurred vision in both eyes. A hospital ophthalmologist found bilateral optic disc swelling, with best-corrected visual acuity of 20/20. She was referred on September 11, 2006, to our institute because of further vision loss that occurred on August 29th. At the initial visit, her best-corrected visual acuity was 60/200 OD and 40/200 OS. Pupillary response to light was prompt and complete bilaterally, and there was no relative afferent pupillary defect. She had marked optic disc swelling but no retinal hemorrhages or exudates in either eye. Fluorescein angiography showed dye leakage only from the optic discs (Figure 1). Visual field testing showed enlarged blind spots and relative cecocentral scotomas in both eyes. Radiographic assessment found no intracranial or intraorbital pathologic conditions. Her erythrocyte sedimentation rate was within normal limits. Blood pressure was 128/76 mm Hg. Stratus OCT revealed hyporeflectivity of the subretinal space in the macular area, which was contiguous to the swollen optic disc at least in the left eye (Figure 2). The hyporeflective space spontaneously disappeared along with resolution of the optic disc swelling in 2 months. Final visual acuity was 20/20 OD and 20/50 OS on May 16, 2008.