Prefoveal floaters as a differential diagnosis to optic neuritis: "mouches dormantes".

This case series describes a new optical coherence tomography (OCT) specific observation relevant to the differential diagnosis of patients with suspected optic neuritis. A tiny prefoveal floater, only detectable by OCT, was found responsible for the symptoms in three patients, one of whom had been referred with unilateral delayed visual evoked potentials. This case series suggests that with increased use of OCT in routine clinical care, entoptic phenomena can be demonstrated as a relevant differential diagnosis to optic neuritis. Patients should be explained the benign nature of their symptoms.