An instrument and method for characterising eye-related optical systems, includingthe live human eye (18) involves scanning an illuminating light beam (22) froma light source and light detector unit (20) from element to element of a beam deflectorarray (12) of elements (14) arranged laterally across the optical axis (16) ofeye (18). At each successive element (14) the illuminating beam (22) is deflectedto form an interrogating beam (24) that is directed into the eye (18) at a peripheralangle that depends upon the lateral location of the deflector element. A returnbeam (23) is reflected or back-scattered from the cornea (38) and returned viathe same deflector element to the light source and detector unit (20). This allowsthe interrogating beams to be scanned sufficiently rapidly into the eye to greatlyreduce the variation of eye fixation and gaze that accompany other methods ofmeasuring peripheral refraction or aberration of a natural eye. In additionto or instead of scanning the illuminating beam (22) over each element (14) ofthe array (12), all or multiple elements (14) of the array (12) can be illuminatedsimultaneously and the multiple interrogating rays (24) thus generated canbe gated by the use of an LCD aperture plate (26). Alternatively, an LCD apertureplate (28) can be interposed between a wide illuminating beam (22) and operatedto selectively illuminate the beam deflector.
