Multifocal electroretinography in multifocal choroiditis and the multiple evanescent white dot syndrome

To study and compare the findings on multifocal electroretinography (MERG) between multifocal choroiditis (MFC) and the multiple evanescent white dot syndrome (MEWDS).

Patients were recruited prospectively from the Department of Ophthalmology & Visual Sciences at the University of Iowa Hospitals & Clinics. They were evaluated using Goldmann visual fields (GVF) and MERG. Patients were diagnosed as having either MFC or MEWDS based on their clinical findings before MERG testing.

Nineteen patients (23 eyes) were included in the study. Eleven patients were diagnosed with MFC and eight patients with MEWDS. Fourteen eyes with MFC and seven eyes with MEWDS were tested with MERG during the acute phase of their respective conditions. Fourteen patients (8 MFC and 6 MEWDS) were followed serially with MERG. Patients with MEWDS demonstrated focal depression corresponding to GVF defects with subsequent near total recovery of the MERG to baseline. Patients with MFC typically demonstrated diffuse loss of function over the entire test field. Focal scotomata, in addition to the diffuse depression, could be identified in 7 of 14 patients. Patients with MFC demonstrated only partial or no recovery of MERG following acute episodes, which was significantly different from the course followed by patients with MEWDS (P < 0.001, Fisher's exact test).

Multifocal electroretinography differentiates MFC from MEWDS. Patients with MFC have permanent damage to the retina with diffuse depression of MERG. Patients with MEWDS, however, typically demonstrate greater focal loss initially on MERG followed by nearly full recovery of first order retinal function.