Difference between Nasal and Temporal Pupil Cycle Time of Koreans

ABSTRACT

A small beam or slit of light focused at the pupillary margin will induce regular, persistent oscillations of the pupil. The period of these cycles is the pupil cycle time that can be easily measured and expressed in milliseconds. When the efferent part of the light reflex of the pupil is normal, determination of the period of these cycles in milliseconds provides a number which may be correlated with conduction time in the anterior visual pathway. Cox and Drews reoorded pupillary response to alternating half-field visual stimuli and found that stimulation of the temporal visual field (nasal retina) caused more pupillary constriction than did equivalent stimulation of the nasal field(temporal retina). These findings imply an asymmertric decussation of pupillomotor pathways in the midbrain in humans as well as greater sensitivity of the nasal retina. We measured nasal and temporal pupil cycle time on 200 normal eyes of Koreans by half-field stimulation of the nasal and temporal retina. And we found that: 1. The mean temporal pupil cycle time was 1071 +/- 92m sec, in right eye and 1068 +/- 81m sec, in left eye. The mean nasal pupil cycle time was 894 +/- 63m sec, in right eye and 899 +/- 57m sec, in left eye. Difference between nasal and temporal pupil cycle time was 177 +/- 73m sec, in right eye and 169 +/- 64m sec, in left eye. 2. The difference of pupil cycle time between the right and left eyes was 3 +/- 84m sec, in temporal retina and 5 +/- 61m sec, in nasal retina. The difference of pupil cycle time between the two eyes was not significant statistically. 3. The mean temporal pupil cycle time of the two eyes was 1069 +/- 85m sec, and the mean nasal pupil cycle time was 897 +/- 62m sec. Difference between nasal and temporal pupil cycle time was 172 +/- 74m sec. In 95% of normal population, the discrepancy between temporal and nasal pupil cycle time was shorter than 253m sec. 4. The mean temporal pupil cycle time was 1066 +/- 86m sec, in male and 1072 +/- 83m sec, in female. The mean nasal pupil cycle time 901 +/- 63m sec, in male and 894 +/- 59m sec, in female. The difference of pupil cycle time between the male and female was not significant statistically.