Electroretinogram amplitudes

Sandberg, M. A., WeigelDiEranco, C., Rosner, B., and Berson, E. L. (1996) The relationship between visual field size and electroretinogram amplitude in retinitis pigmentosa. Invest. Ophthalmol. Vis. Sci. 37,1693-1698. 

As reported by Benolken (1973), the amplitudes of both the a and b-waves of an electroretinogram decreased significantly as aresultof ALA deficiency in rat (Watanabe, 1987). A diet supplemented with soybean oil (1.5 en% as ALA) did not give maximum amplitudes similar to those observed in the perilla-oil group (Fig. 4). 

Fig. 4. Amplitudes of a- and b-waves in the electroretinogram in rats fed a semipurified diet supplemented with safflower oil or perilla oil, or a conventional diet supplemented with soybean oil. The intensity of the dim light corresponded to 3 in the abscissa, and that of the bright light was 1000 times higher.

Finally, there are also bioelectric currents flowing in the retina. They are detectable using corneal electrodes, and the monitored biopotential is known as an electroretinogram (ERG). It changes in amplitude and waveshape with pulsed illumination. A strobe light, for example, will produce a transient ERG biopotential of nearly 1 mV. 

Ocular electrophysiological changes induced by anesthetics have been reported in laboratory animals. Granit has shown that ether inhalation markedly decreased the amplitude of the visual evoked potentials (VEP). The amplitude of the electroretinogram (ERG) is known to decrease with anesthesia" ... 

Cats fed a taurine-free, casein diet develop retinal taurine deficiency and subsequently photoreceptor cell death. (Berson, Hayes, Rabin, Schmidt, and Watson, 1976 Schmidt, Berson and Hayes, 1976 Schmidt, Berson, Watson and Huang, 1977). Supplementation of this diet with methionine, cysteine, inorganic sulfate, vitamin B., or vitamin B plus cysteine did not prevent development of retinal taurine deficiency and retinal malfunction. A synthetic amino acid diet devoid of casein and taurine also resulted in retinal taurine deficiency and retinal malfunction. Only taurine-containing diets (i.e., chow or casein plus taurine) preserved normal retinal taurine concentrations arid electroretinogram (ERG) amplitudes. These findings have firmly established a role for exogenous taurine in maintaining normal retinal function in the cat. 

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