The influence of iris color on the pupillary light reflex

Abstract 

· Background: This study was carried out to investigate the effect of iris color on the pupillary light reflex (PLR) in normal healthy volunteers. · Methods: Pupil perimetry was performed on 50 healthy volunteers with the Octopus 1-2-3 automated perimeter. Within the 30-deg visual field, 33 test locations were investigated four times. Stimulus parameters were Goldmann size V (1.72°), intensity 1632 cd/m², stimulus time 200 ms, background illumination 0 cd/m², and interstimulus interval 3 s. Pupillometric parameters studied were initial pupil size, amplitude (magnitude of pupillary contraction), latency time, contraction time, pre-PLR movement, contraction velocity, and redilation velocity. Pupillometric parameters were investigated by analysis of variance by the independent variables blue and brown irides. · Results: Iris color (blue vs brown) influenced statistically significantly (P<0.05) amplitude (0.504 mm vs 0.594 mm), contraction time (401 ms vs 407 ms), contraction velocity (13.75 mm²/s vs 16.01 mm²/s), and redilation velocity (4.80 mm²/s vs 5.66 mm²/s). Iris color did not influence initial pupil size (4.78 mm vs 4.83 mm), latency time (520 ms vs 521 ms), and pre-PLR movement (0.328 mm²/s vs 0.325 mm²/s). · Conclusions: Pupillary contraction amplitude and velocity depended on iris color, whereas pupil size and latency time were independent of iris color. Therefore, iris color might be considered when evaluating pupillary movements in pupil perimetry.