The eye - breaking environments are cornea and lens, the cornea is about 2/3 of total irritation and the lens is 1/3. The optical structure of the eye can be likened to the camera. The amount of light entering the eye is controlled by the pupil and this structure corresponds to the lens aperture in the camera. Cornea and lens in the eye of the lens system of the camera in the camera, and the retina of the web are the counterpart of the photofilm.