Abstract
Purpose::
To report the first multifocal ERG data in a case of ocular quinine toxicity, and to relate it to full field ERG data.
Methods::
A 43 years old woman was examined 9 months after quinine intoxication taken as a suicide gesture. Visual acuity was 20/20 OU. Perimetry, color vision, dark adaptation, EOG, ganzfeld ERG and multifocal ERG (VERIS 103 elements, Lmean 100 cdm-2, 10-100 Hz, Burian-Allen electrode) studies were performed. ISCEV recommendations were followed. In addition, the ERG was recorded to high energy flashes.
Results::
Goldmann visual fields (III4e) were oval 60 deg horizontal, 40 deg vertical for each eye. HVF 30-2 foveal thresholds were normal (35-36 dB) but at 2 deg eccentricity sensitivity had reduced to 10 dB below average. The ISCEV ganzfeld ERG showed the characteristic negative waveform for photopic and scotopic standard flashes. MfERG response densities were reduced at all locations. The center element and first 2 rings of elements (0 deg - 5.5 deg) generated electropositive waveforms (mean P1/N1 [b/a] ratio = 2.1, SD 0.3. Normal = 2.9). From 9 deg to 19 deg eccentricity, waveforms became progressively more electronegative. At all locations, N1 and P1 are reduced. Second order responses change systematically with eccentricity. The high energy flash ERG shows a normal rod Rmax indicating preserved receptor function, despite loss of 87% of visual field area. The retinas show gross vascular attenuation.
Conclusions::
The normal visual acuity and visual sensitivity in this patient are associated with foveal mfERG waveforms that are electropositive, and that are relatively better preserved. These data show the previously unknown gradient of retinal function from the fovea to blind peripheral retina.
Keywords: electroretinography: clinical • retina: distal (photoreceptors, horizontal cells, bipolar cells) • drug toxicity/drug effects