Method and apparatus for objective electrophysiological assessment of visual function

Abstract

For electrophysiological assessment of visual function using a head mounted stereo display (e.g. virtual reality goggles) for displaying a stimulus which is used to generate a retinal or cortical response. In particular, a method for objective electrophysiological assessment of visual function of at least one eye of a subject includes presenting a visual stimulus to at least one eye of the subject, recording at least one of a retinal response and, a cortical response generated as a result of the presenting; analyzing said response and, as a result of said analyzing, forming a map of the visual function of the at least one eye of the subject 6. The invention also relates to as system for such electrophysiological assessment.

1 . An apparatusus for analysing at least one multifocal visual evoked potential response of at least two subjects, the at least one visual evoked potential response being induced by any mode of multifocal stimulation, wherein the stimulation mode is adapted to simultaneously stimulate different parts of the visual field of an eye of the subject such that different parts of the visual field are stimulated with random sequences of different timing or character, the apparatus comprising:
 (a) electrodes placed on the scalp or in contact with the eye of each subject configured to simultaneously record (A) the at least one visual evoked potential responses from each of the different parts of the visual field of the eye and (B) the subject's overall spontaneous brain activity levels; and   (b) a computer configured to:   (bi) identify, for each subject, the alpha rhythm component in the subject's overall spontaneous brain activity levels,   (bii) remove, for each subject, the alpha rhythm component from the subject's overall spontaneous brain activity levels;   (biii) calculate, for each subject, a corresponding scaling factor, the scaling factor being derived from the subject's overall spontaneous brain activity levels from which the component of alpha rhythm is identified and removed; and   (biv) scale, for each subject, each subject's visual evoked potential response using said each subject's scaling factor such that the variability of the visual evoked potential responses induced by the multifocal stimulation between the at least two subjects is minimised.   
     
     
         2 . The apparatus of  claim 1 , wherein the alpha rhythm component in the subject's overall spontaneous brain activity levels is identified by wave component analysis. 
     
     
         3 . The apparatus of  claim 2 , wherein the alpha rhythm component in the subject's overall spontaneous brain activity levels is identified by Fourier analysis. 
     
     
         4 . The apparatus of  claim 1 , wherein step (bi) comprises:
 for each subject, using Fourier power spectrum analysis to determine the subject's overall spontaneous brain activity levels, thereby to calculate a scaling factor.   
     
     
         5 . The apparatus of  claim 1 , wherein the multifocal stimulation stimulates responses from different parts of the visual field of both eyes of the subject and the responses from each of the different parts of the visual field for each eye are recorded simultaneously. 
     
     
         6 . The apparatus of  claim 1 , wherein the computer is further configured to:
 (bv) identify and remove the effect of electrocardiogram spikes.   
     
     
         7 . The apparatus of  claim 3 , wherein the electrocardiogram spikes are identified by Fourier analysis of the subject's recorded overall spontaneous brain activity levels. 
     
     
         8 . The apparatus of  claim 1 , further comprising at least one of storing and displaying said evoked potential response.