We present detailed ophthalmic findings in a case of tuberculum sellae meningioma with acute visual symptoms due to optic canal involvement. A 62-year-old Japanese woman reported a 1-week history of headaches and blurred vision in her left eye. Her visual acuity was 0.3 in the left eye with no ophthalmoscopic abnormalities. A relative afferent pupillary defect and inferior temporal field defect were found in the left eye. Pattern visual evoked potentials were undetectable in the left eye. Enhanced magnetic resonance imaging showed a 9 mm intracranial lesion around the left optic nerve anterior to the chiasm. She was diagnosed with granulomatous inflammation because of the increased cell counts and protein concentration in the cerebrospinal fluid. She was treated with steroid pulse therapy, and her visual acuity and visual field defect improved to normal in 3 weeks. However, 16 months after the onset, she suffered from headaches again and had a complete loss of vision in her left eye. There was no response to steroid pulse therapy. Enhanced magnetic resonance imaging revealed that the lesion had extended into the left optic canal, and emergency tumor removal surgery was carried out. The histopathological diagnosis was meningioma. One month after the surgery, her left visual acuity improved to 1.2, and her visual field was almost normal. Pattern visual evoked potentials were present but had a prolonged P(100) latency of 170 ms. A thinning of the ganglion cell complex was detected by optical coherence tomography. Ophthalmologists should be aware that a small tuberculum sellae meningioma can cause acute visual symptoms due to optic canal involvement. Early consultation with a neurosurgeon is necessary. Visual evoked potentials and optical coherence tomography are sensitive and helpful in following patients with optic nerve compression.