1. A method for assessing the nervous system of a subject, the method comprising the steps of: presenting multifocal arrays of stimuli in alternating volleys of individual stimuli selected from at least two stimulus ensembles that are clustered within portions of a sensory field of a subject adapted to evoke pupillary responses from at least one pupil of the subject, said clustered stimulus ensembles comprising a plurality of individual stimuli drawn from portions of the field surrounding the centre of the sensory field defined within a first inner radius to a second outer radius and from a first polar angle to a second polar angle, selected individual stimuli being concurrently presented according to statistically independent sequences such that on any time step that a volley of stimuli are presented from a given cluster such that each individual stimulus element has a probability of being presented of about 0.5, the presentation of the stimuli in such volleys overcoming gain control mechanisms that otherwise tend to diminish the responses evoked by the stimuli and thus produce large and more reliable responses from the pupil; detecting using a sensor responses of at least one pupil evoked by the stimuli; recording and relating the pupillary responses to the function of the subject's neural responses to at least two of the individual stimuli of the clustered ensembles; and determining weight functions for each region of the sensory field tested from the recorded responses of pupil for assessment of the sensory system.