Infrared video pupillometry: A method used to measure the pupillary effects of drugs in small laboratory animals in real time

Abstract

Pupillometry in clinical investigation and in basic research often requires dynamic measurement of pupil size. Static methods, i.e. direct observation and still photography, are often used because of the high cost of commercial infrared pupillometers and problems with pupil-iris contrast in small animals. This report describes an improved infrared video pupillometer (IVP) which accurately measures the pupil area of small animals in real time (30 samples/sec). Two components of the pupillometer were designed and built by the authors: a “bright-pupil” infrared illumination system and a digital video signal processor (VSP). The use of a standard closed-circuit television camera to produce the pupil image signal results in a device that is relatively economical to construct. The IVP is sensitive enough to accurately track pupil are in the study of the pupil light reflex or pupillary oscillations. Several applications for the IVP are illustrated, including analysis of the transient response to light flashes and intravenous injections of drug, and analysis of spontaneous and drug-induced pupillary fluctuation. Pupillography has been applied in the bioassay of various psychopharmacologic compounds and in the assessment of narcotic dependency. This IVP is being used in this laboratory to study the pupillary action of opiates in the rabbit and rat.