The electroretinogram (ERG) is a measure of electrical activity of the retina. It is typically recorded from the cornea with a wire electrode or gold-foil electrode. Generally, the the ERG is considered to reflect the retinal processing of a light stimulus, typically a photoreceptor response followed by secondary neuronal activity and electrical activity evoked by supportive Muller cells.
I am wondering if the pupil response will add signal on top of the ERG? Firstly, there is the direct pupil response, which causes the pupil to constrict when the eye is subjected to bright light. Pupil constriction may, perhaps, induce electromyogram (EMG) activity when the smooth sphincter muscle around the pupil contracts, which in turn could theoretically contaminate the ERG. Secondly, there is neuronal activity involved in constricting the pupil, as light is processed in the retina by ganglion cells that in turn drive the pupil reflex. Furthermore, there is the consensual pupil response as well. This response causes the contralateral pupil to constrict when the ipsilateral eye is subjected to bright light. The consensual response is mediated by efferent input from the brain following stimulation of the other eye and causes both eyes to restrict. Hence, neural input arrives in the contralateral retina from the brain. This activity is not directly related to the processing of the light stimulus and may disturb the ERG proper when ERGs are recorded with a flash and both eyes are open.
So my question is
- Does a pupil-mediated EMG affects the ERG signal?
- Does neuronal activity involved in the pupil reflex affect the ERG, for example the efferent input involved in the consensual response?
I have had no luck after extensive searches in text books, Scopus, Pubmed, Google, Google Scholar.