Purpose: To describe the management of a case of an arachnoid cyst of the optic nerve.

Methods: Here, we report a 27-year-old female patient who was diagnosed with arachnoid cyst of the left sheath optic nerve, drained in several occasions, and came to our service because of progressive blurring in the left eye.

Outcomes: Due to the location of the lesion, excision could not be performed; so we performed a microsurgical incision with drain by nasal superior transconjunctival approach. After that, the visual acuity (VA) was 0.7, and we could observe that the size of the cyst was smaller than previous examinations with magnetic resonance imaging (MRI). Nowadays, the patient keeps the same asymptomatic VA. So medical appointments are planned to closely follow-up, and periodically, we perform new scan images and visual fields.

Conclusions: Arachnoid cysts of the optic nerve are rare, benign, slowly progressive conditions. They can be asymptomatic lesions, especially smaller ones, or may result in proptosis and loss of vision because of the compression. The best imaging examination for their follow-up is MRI. They should be differentiated from optic nerve sheath meningioma and other conditions.