BACKGROUND: The ganzfeld electroretinogram (ERG) provides information about diffuse retinal function while the multifocal ERG (mfERG) provides information about localized cone function across the macular region. These tools were used in two cases of AZOOR, providing new information on the spectrum of ERG findings in this retinal disease. AZOOR is a rare disorder of unknown etiology first described by Gass in 1993. Symptoms include photopsias and visual field loss. The ERG changes are consistent with a photoreceptor disorder, and in the early stages there can be minimal or no retinopathy. Unlike retinal dystrophies, a hallmark of the ganzfeld ERG in AZOOR is interocular asymmetry. The two cases reported here are unique in that the ganzfeld ERG becomes barely recordable in one case, and the multifocal ERG has a unique topography in the other. Furthermore, one case is followed for 14 years, the longest time reported in the literature to date.
CASE REPORT(S). Case 1: DM is a 54 years old woman first seen in 1986 with complaints of photopsias and visual fading. Best corrected visual acuities (BCVA) were 20/15 OU. In 1990 BCVA’s were OD 20/15, OS 20/40 and a ganzfeld ERG showed a unilateral left reduction in amplitudes and delays in implicit times. Right eye ERG responses were normal. By 1993 BCVA’s were OD 20/15, OS 20/200. In 1997, for the first time the right eye was found to have reduced BCVA of 20/25, while the left was 20/750. Today the BCVA’s are OD 20/100, OS HM. The ganzfeld ERG for the better right eye shows greater cone functional loss than rod loss, and the ERG for the left eye is barely recordable for all conditions. Longitudinal Goldmann perimetry data are presented.
Case 2: ER is a 28 years old man who noticed a sudden onset left eye paracentral scotoma with mild photopsias. Visual acuities are 20/16+2 OU. The ganzfeld ERG OD is normal, while OS shows much greater cone dysfunction than rod dysfunction. The mfERG responses are normal OD, while OS shows a normal foveal response and greatly reduced responses parafoveally. The mfERG therefore shows an unusual annular loss.
CONCLUSIONS. AZOOR can be difficult to diagnose without an ERG. The ganzfeld and mfERG can be highly abnormal in the presence of excellent visual acuity. The annular ERG loss in Case 2 probably corresponds to the Acute Annular Outer Retinopathy, previously described as a variant of AZOOR (Gass & Stern, 1995).