An objective means of estimating the gross function of the visual system is provided by measurement of the electrical activity produced by light stimulation.1 The electroretinogram recording, as described by Karpe, for example,2 gives one means of estimating retinal function. Until recently, evoked potentials produced at the occipital cortex have not received much attention, mainly because of difficulties associated with the measurement and interpretation of such small signals. The introduction of computer techniques has provided a new stimulus for these measurements, as under certain conditions small signals can be extracted from an obscuring noise background. A large general purpose computer3 has almost unlimited potential in this respect, while for fairly specific purposes a small machine of the Average Response Computer type is very effective.4 Several specialized instruments have been described,5-11 and the commercially available Computer of Average Transients is finding increasing use.
The fundamental technical
FRICKER SJ. Numerical Measurements of Retinal and Occipital Function. Arch Ophthalmol. 1966;76(1):37-46. doi:10.1001/archopht.1966.03850010039010