Measurement of Retinal Function Using the Electroretinogram

Abstract

In our waking hours, we are continually being subjected to a vast amount of information that needs to be analyzed and interpreted by the visual system. If we consider the simplest case of viewing a single object against a uniform background, we need to know, among other things, the brightness and color of both object and background, the object’s speed and direction of movement, its distance and its size. If more than one object is involved, as is usually the case, one not only needs to know these parameters for each object, but also how they relate to one another. The interface between this complex visual environment and our nervous system is the retina; a thin translucent layer of nerve cells lining the posterior half of the eye. The optic media, primarily the cornea and, to a lesser extent, the lens, produce an inverted optical image of the world on our retina. As described in the previous chapter, the photons that make up this image are then absorbed by the visual pigment and converted into a series of electrical events in the photoreceptors through the processes of transduction. These electrical signals are then processed by the remainder of the visual system to extract all the relevant stimulus parameters. Although much of this processing occurs within the brain, a surprising amount is carried out within the retina itself. This is especially true for lower vertebrates such as amphibia and fish.