Multifocal electroretinogram (mfERG) in a family with occult macular dystrophy (OMD)

Localized macular dysfunction, in Stargardt macular dystrophy for example, is frequently not detected by Ganzfeld electroretinography (ERG) but it may be detected by methods such as focal macular electroretinogram and pattern electroretinogram at the posterior pole of the eye or indirectly by recording of the visual evoked cortical potentials (VEP). The multifocal electroretinogram (mfERG) is a new diagnostic tool allowing analysis of local bioelectrical signals of circumscript areas across the macular region. Miyake recently described a type of macular dystrophy, which he termed "Occult Macular Dystrophy" (OMD) because of a normal fundus aspect and functional deficit even in aged patients. This is a case report about a family with a presumed OMD where mfERG demonstrated a central depression in the affected family members.

Three members of a family with a suspected autosomal dominant trait complained of a reduced visual acuity since early childhood. The fundus of all patients appeared normal without signs of a maculopathy. The first order mfERG (ROLAND system) was recorded using 61 hexagons.

The signals arising from the macular region of the 6 eyes (3 affected family members) were selectively depressed while the signals from the paracentral area were much less impaired. Statistical analysis of the mfERG signals (concentric hexagon rings) confirmed the central depression with a better performance of the peripheral rings.

A new family with OMD is added to preceeding reports. A reduced visual acuity without visible fundus abnormalities may be misdiagnosed as amblyopia, optic nerve disease or nonorganic visual disorder. The mfERG offers the diagnostic tool to detect a circumscript retinal/macular dysfunction by a single procedure.