to an electrical signal from the eye 44 that is sensed by the electrodes 32 34 for example it could be electrodes 32 36 contacting the skin of the patient proximate to the eye 44 and the electrical signal is communicated by wires 48 to an amplifier and a d converter shown as block 50 the amplifier is preferably a biomedical amplifier using 24 bit analog to digital converters that eliminates gain adjustment and the prolonged recovery from saturation of conventional amplifiers typically conventional amplifiers have required some oversight by a technician during testing to assure that the gain setting was correctly matched to the input range of the analog to digital converter further such conventional amplifiers could saturate fail to respond to the input signal and might take tens of seconds to recover the ability to respond to a signal the saturation is difficult to distinguish from a lack of response from the patient making reliable automation of signal acquisition difficult to avoid the problems in a preferred embodiment the system used a low gain differential amplifier no more than 32 u00d7 and a high resolution typically 24 bit differential analog to digital converter to acquire the signal from the eye 44 by means of the skin electrodes 32 34 thus the amplifier has a very high tolerance for noise and offsets while producing highly faithful reproduction of the input waveform the amplifier and a d converter of block 50 are also immune to prolonged saturation caused by interfering signals input impedance of the system is.