Initial Pupil Diameter Research Articles

Repeatability of dynamic eye pupil response measurement using the Pupilscan instrument

The repeatability of pupil response measurements made with the Pupilscan instrument has been assessed. Two operators made 32 repeat recordings of the pupil response in each eye of eight normal subjects over four days. A total of 512 recordings were made and the results analysed by variance analysis. Room light levels were carefully controlled. The instrument measured initial pupil diameter, and after a 0.2 s light stimulus measured minimum and final diameters, maximum diameter change, constriction velocity and time to minimum diameter. For all measurements except time to minimum, there were significant differences (P less than 0.001) between the normal subjects. Day-to-day variation was also significant (P less than 0.005), but did not mask the differences between subjects. It is concluded that the average of at least four repeat measurements are made, giving error ranges similar to those observed from day-to-day changes.

Genetic influences in drug responses of the eye and the heart.

1. Pupillary responses to locally applied phenylephrine and cardiac responses to intravenous hyoscine N-butylbromide have been studied in ten pairs each of healthy monovular and binovular twins aged between 24 and 60 years. 2. Under identical lighting conditions resting pupil diameters differed widely among individuals, being greater in female subjects and in those with larger irides and smaller with increasing age. 3. Monovular twins, but not binovular twins, showed significant concordance in iris diameter, initial pupil diameter, initial heart rate and responses to both drugs. The results suggest that these responses were dependent on the concordance of peripheral sympathetic and parasympathetic tone within each twin pair. 4. It is concluded that much of the variability in response to drugs acting on the autonomic nervous system is determined by physiological factors and that these are genetically influenced.

Positive correlation between initial pupil diameter and amplitude of miotic response to pilocarpine in rabbits and to carbachol in man.

A linear correlation between amplitude of miotic response and initial pupil diameter has been demonstrated in rabbits using various concentrations of pilocarpine HC1. The same correlation was found when published results in humans using carbachol were examined and it is likely that the correlation also applies to pilocarpine in humans. No such correlation was observed with physostigmine.