remote location e g anywhere in the world linked by the internet where the optical data analysis system 17 see fig1 is implemented the output data from the output system 19 may be transferred back through an access link to the display of results 21 or to another location if desired the illumination and optics systems of fig2 and 7 provide a means for projecting illuminating light into the eye with an intensity varying periodically at a selected frequency and means for detecting the light reflected from the retina and particularly the fovea centralis to provide a signal corresponding to the intensity of the detected light any other elements which similarly project light into the eye and detect the reflected light may be utilized examples of such alternative means are illustrated in fig8 and 9 although it is understood that these are exemplary only of such structures the illumination and optics systems of fig8 and 9 are arranged to help reduce the intensity of the light reflected from structures of the eye other than the retina and particularly to reduce the effect of light reflected from the surface of the cornea in the illumination and optics system of fig8 the light projected from a source 31 such as an led expands in a beam 32 which is received by a lens 33 which directs the beam to a polarizing beamsplitter 35 the polarized beam 36 that exits the beamsplitter is passed through a lens 37 and an eyepiece lens 38 to the eye 10 where the lens of the eye focuses the beam onto the fovea 39 of the retina the light reflected from the retina and particularly the fovea 39 and from other eye.