Abstract
Two technical problems which have presented considerable difficulty in experimentation on human vision are (1) providing a satisfactory “artificial pupil” through which a beam of light may enter the eye unmodified by the contraction and dilation of the real pupil of the eye, and (2) providing a stable electrical connection with the cornea for the purpose of making continuous records of polarity and action potentials of the retina.
The first of the above problems is met in the present experiments by coating the central portion of a contact lens† with black enamel, leaving an opening of the desired aperture in the exact center of the lens (Fig. 1). This arrangement has the advantage that a diffuse field of light may be used for stimulating the eye. The subject merely sits at a convenient distance from the stimulus field and fixates normally upon a fixation point, without the discomfort of maintaining a rigid posture of the head. Since the artificial pupil moves with the eyeball, small head and eye movements will not interfere with the transmission of the stimulating light to the retina.
The second problem mentioned above, that of maintaining an electrical contact with the cornea, is met by the use of a corneal electrode mounted upon a contact lens as shown in Fig. 1. The electrode consists of a silver disc cemented into a hole in the contact lens. The surface of the disc is flush with the inside surface of the lens. A fine, flexible wire, supported by beeswax, is employed as a lead from the electrode. When the lens is inserted into the eye, the silver makes contact with the physiological saline solution between it and the cornea.
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