Patent ID: 7942528

Claim:
A perimeter for measuring a visual field in a state that an examinee fixates a predetermined fixation point, comprising: stimulus presentation means for successively presenting stimuli having predetermined luminance at various positions in a visual field of an examinee; operation means to be operated by said examinee who perceived said presented stimulus; visual field judging means for judging said visual field of said examinee based on signals from said stimulus presentation means and said operation means; and fixation state judging means for individually judging fixation state of said examinee every said stimulus in connection with each presented stimulus whenever said stimulus is presented; said fixation state judging means including a fixation state detecting portion for detecting a fixation state of an examinee, a criterion outputting portion for outputting criterions for judgment of said fixation state, a comparison judging portion for judging said fixation state by comparing a signal from said fixation state detecting portion with a signal from said criterion outputting portion, and a judged result output portion for outputting a judged result in connection with each presented stimulus based upon signals from said stimulus presentation means and said comparison judging portion; said fixation state detecting portion having a photographing portion for obtaining successive images by photographing a front eye portion of an examinee and an image processing portion for processing said images obtained by said photographing portion so as to extract a pupil of said examinee and obtaining a center of said pupil; said criterion outputting portion having a first criterion for judging a fixation state based upon a position of said obtained center of said pupil and a second criterion that is smaller than said first criterion; whereby said comparison judging portion judges “defective fixation” if said position of said center of said pupil obtained by said fixation state detecting portion is the first criterion or higher, and judges “may be defective fixation” if said position of said center of said pupil is between first criterion and said second criterion, and judges “no defective fixation” if said position of said center of said pupil is said second criterion or lower.