Clinical ERG findings in ethambutol intoxication

Abstract

The human electroretinogram (ERG), evoked by white flashes of extremely short duration (10 microseconds), shows a typical dependence on flash intensity. Increasing stimulus intensity increases the amplitude of the a-wave until saturation is reached. The amplitude of the b-wave reaches a maximum value with flashes of middle intensity, then decreases at higher stimulus strengths. The values of a-wave amplitude saturation, defined as 100%, may serve as a basis for standardizing the various amplitude-intensity relationships of the a- and b-wave. The b-wave function, calculated in this way, shows different maximum values depending on whether it was determined after light adaptation or in dark adaptation and low interindividual variability. However, the difference between bmax in dark and light adaptation is markedly decreased in the case of ethambutol intoxication. ERG changes are only detected in severe cases (total central scotoma) and are below the discrimination level in cases with moderate symptoms (relative central scotoma, visual acuity greater than 0.4-0.5).

Abnormal Multifocal Electroretinogram (mfERG) in Ethambutol Toxicity

“…2,19−22,25−28 On the other hand, Babel et al 23 found abnormal ERGs in one-third of 38 patients with EMB toxicity. Hennekes 24 reported abnormal ERGs in three severe cases of EMB toxicity and observed that the abnormalities were not present in moderate cases (less severe central scotoma and visual acuity). Kohler et al reported EMB injection into the vitreous of fish.…”

Cannabinoid Receptors CB1 and CB2 Modulate the Electroretinographic Waves in Vervet Monkeys

“…These findings might be helpful for the development of new pharmacological targets for the treatment of retinal intoxication [ 67 , 68 ] and diseases [ 69 ]. These retinal pathologies are generally associated with a decrease in the amplitude of the electroretinographic waves.…”

Multifocal ERG in ethambutol associated visual loss

“…Previous studies have found abnormalities in the visual evoked potentials, 9 full field ERG and EOG in patients with presumed ethambutol optic neuropathy. [10][11][12] In experiments on fish, ethambutol altered synaptic connections between horizontal cells and cones in a dose related fashion, resulting in degeneration of the cone pedicles. 13 In our study, the N1 amplitude was found to be significantly lower in the ethambutol treated patients compared to age matched controls.…”