Abstract: A method is disclosed for measuring glare-induced vision blockage in a subject, as are apparatus for performing the method. According to the method, a glare-inducing light is shined in the subject's eyes. A series of visually-perceivable patterns of varying apparent sizes, each pattern arranged around the light, is presented to the subject. Each pattern comprises a sequence of alternating light and dark segments. The pattern is preferably in the form of a broken outline of a circle centered on a window through which the glare-inducing light passes. For each pattern presented, the subject is asked to indicate which if any dark segments he perceives. The subject may also be asked how many dark segments he sees and in what locations. The smallest pattern whose dark segments can be perceived by the subject indicates the size of the subject's glare-induced vision blockage.