Arachnoid cyst of the intraorbital portion of the optic nerve with unilateral disc oedema and transient shallowing of the anterior chamber. A case report.

An unusual occurrence of chronic monocular disc oedema, visual loss and shallowing of the anterior chamber in a patient with an arachnoid cyst involving a portion of the intraorbital optic nerve was reported. Decompression of the optic nerve sheath through a Krönlein approach was followed by prompt deepening of the anterior chamber and a gradual, delayed relief of the disc oedema. It is concluded that orbitotomy and decompression of the optic nerve sheath should be done before atrophic changes of the optic nerve and visual loss begin to develop.