Page:Latency of Pupillary Reflex to Light Stimulation and Its Relationship to Aging.djvu/5

Rh Kumnick (1956) stated that the latency period of pupil constriction is not affected by increasing age but is affected significantly by the pupillary conditions of restitution and decay of restitution at certain age levels.

The over-all features of the instrumentation used for pupil latency measurements are shown in the block diagram of Figure 2 and the photograph of Figure 3. The basic instrument is the Electronic Pupillograph (10, 14). It consists of a scanner, an amplifier-detector assembly and a stimulator.

The scanning unit is a rotating drum with slits in its periphery through which a light beam is projected. This beam is divided into two identical paths which scan both irises in rectangular patterns, comprised of twelve horizontal lines, at a rate of sixty times per second. A Wratten 87C filter placed between the drum and the eye renders the scanning light invisible to the dark adapted person. The light of the two scanning beams is reflected onto two photoelectric cells. The outputs of these cells are amplified in two identical channels and converted into DC analog voltages, whereby the voltage amplitudes are proportional to the largest' horizontal diameters of the pupils.

The stimulator lamp energy is reflected from a mirror located just above the optical path of the infrared scanning unit. The same mirror is used to reflect a dim, red fixation light which is placed on the ceiling above the scanner at a distance of four feet. The line of regard and the direction of the stimulating light beam are 15° above horizontal.

The Grass Photic Stimulator (model PS-2) provided a high intensity flash of approximately one million peak candle power for 10 microseconds. The flash was seen by the left eye only, while measurements of latency period were obtained from the consensually reacting right pupil. For these measurements, the derivative of the Electronic Pupillograph scanner voltage was used rather than the analog voltage which represents the pupil