The pupillary reflex is a natural reaction to visible optical irradiation. In particular in a beam cross-section which is larger than the normal pupil diameter, the pupillary reflex limits together with the aversion responses the duration and the extent of exposure.
The increasing availability and the associated hazards of handheld laser products in the entire visible spectrum and the currently still limited knowledge of the anatomic and physiologic function of the pupillary reflex were the special reason for the study of power, exposure duration and wavelength dependence on the pupillary reflex.
Various test setups have been realized and the most important parameters of the pupillary reflex like latency period, constriction duration, maximum amplitude, and relaxation time were investigated. The measurements were made with the help of infrared pupillography. The subsequent analysis was performed on a video recording with a frame rate of up to 120 Hz.
The tests were carried out at the wavelengths of 405 nm, 532 nm, 635 nm and 670 nm. The applied laser beam powers ranged from about 0.5 microwatts up to 300 microwatts and the exposure durations have been chosen between 25 ms up to 10 s. The investigations have been performed with several test subjects under normal laboratory illumination, mesopic conditions and after dark adaptation.
The measurement results showed that the latency times are in the range of 160 ms to 280 ms. The investigations also showed that all other parameters of the extent of the pupillary reflex depend on the power level, exposure duration and on the applied wave-length. In this context, it could be shown that, for example, violet laser radiation at 405 nm caused a larger pupil response as energetically equivalent red laser radiation and showed a nearly equivalent response as for 532 nm.