Acute idiopathic blind spot enlargement syndrome (AIBSE) is a rare peripapillary outer retinopathy with overlap within the white dot family of chorioretinopathies. It can be mistaken for optic neuritis due to the apparent vision loss and positive visual phenomenon but unlike optic neuritis there is no pain on eye and no optic neuropathy (loss of vision, colour vision deficit, RAPD, disc swelling). It is less likely IIH as the impairment is unilateral and there is no disc swelling and no symptoms of IIH (headache, pulsatile tinnitus, transient loss of vision). Optic perineuritis can present like this but typically there is pain, a RAPD/optic neuropathy and MRI findings of swollen and enhancing perineural tissue.

AIBSE is a self limiting condition with a good prognosis. In our case the patient had a likely overlap with MEWDS (multiple evanescent white dot syndrome) given the fundus autofluoresence changes around the disc. It is characterised by an acute inflammatory phase, involuting phase, chronic phase then recovery phase. Other useful tests are multifocal ERG and FFA.

The subject was motivated to decrease the length of her symptoms and was keen to trial oral prednisone which likely shortened the duration of symptoms. She had blood testing for autoimmune and infective causes which were normal and an MRI with contrast which was also normal. She retained normal vision throughout and had a shrinking of the enlarged blind spot with persisting photopsiae (a common finding in AIBSE).