Abstract: The present invention provides an ophthalmic device to diagnose the circulation of blood in an eye fundus by producing a pair of plethysmograms for synchronized comparison. A pair of fiber optic conduits are attached to a coupler that can be sealingly affixed to the exterior surface of the cornea of an eye. The coupler can be attached to the exterior surface of the eye by the application of subatmospheric pressure within the coupler. Light is introduced on the axis of the pupil through a central light exit region that is physically small enough relative to a dilated pupil to prevent the reflection of light from the iris. The light reflected from the eye fundus is received in a peripheral light receiving region. The light signals are converted into electrical voltage levels that are ultimately used to produce a visual display of the plethysmograms.