OPHTHALMIC APPARATUS

PURPOSE:To enable highly accurate measurement of eye refractivity by eliminating the influence of external light by obtaining the data free from the influence of external light by comparing and computing the images projected on a photo- reception device when measuring light is projected and not projected. CONSTITUTION:The projected image projected on the photo-reception device or the corresponding data when measuring light is not projected on a subject's eye and the projected image on the photo-reception device or the corresponding data when the measuring light is projected on the subject's eye and stored in the second frame memory 16 and the first frame memory 15 respectively. Then the image or the data when the measuring light is projected on the subject's eye and the image or the data when the measuring light is not projected are compared each other by a processing unit 18. The data free from the influence of external light is obtained, e.g. from the difference between the data of the former and the data of the latter corresponding to the data of the former, from the difference between the outputs of the photo-reception unit 9 or from the difference between the quantities of light. Thus an accurate refractivity of the eye can be determined by calculating the data free from the influence of external light.