Pupillary behavior in relation to wavelength and age

Abstract

Pupil light reflex can be used as a non-invasive ocular predictor of cephalic autonomic nervous system integrity. Spectral sensitivity of the pupil's response to light has, for some time, been an interesting issue. It has generally, however, only been investigated with the use of white light and studies with monochromatic wavelengths are scarce. This study investigates the effects of wavelength and age within three parameters of the pupil light reflex (amplitude of response, latency, and velocity of constriction) in a large sample of younger and older adults (N = 97), in mesopic conditions. Subjects were exposed to a single light stimulus at four different wavelengths: white (5600°K), blue (450 nm), green (510 nm), and red (600 nm). Data was analyzed appropriately, and, when applicable, using the General Linear Model (GLM), Randomized Complete Block Design (RCBD), Student's t-test and/or ANCOVA. Across all subjects, pupillary response to light had the greatest amplitude and shortest latency in white and green light conditions. In regards to age, older subjects (46–78 years) showed an increased latency in white light and decreased velocity of constriction in green light compared to younger subjects (18–45 years old). This study provides data patterns on parameters of wavelength-dependent pupil reflexes to light in adults and it contributes to the large body of pupillometric research. It is hoped that this study will add to the overall evaluation of cephalic autonomic nervous system integrity.

A Novel Visual Psychometric Test for Light-Induced Discomfort Using Red and Blue Light Stimuli Under Binocular and Monocular Viewing Conditions

“…However, past psychophysical studies have largely predated the discovery of the melanopsin system and thus did not account for its properties in their methodological design. 21,[27][28][29][36][37][38][39][40] For example, retinal response features differ with stimulus wavelength, 41 and given the photoncounting feature of the ipRGC system (namely a sustained pupillary constriction that persists after stimulus offset 6 ), a preexposure bias likely exists, particularly in studies that evaluate chromatic responses separately. 21,42 In addition, variable pupil diameter across trials may have altered the proportion of photons that reach the retina, thus two different light intensities may have elicited a similar perceptual experience and biased the discomfort thresholds generated.…”

Reply: Pupil area and photopigment spectral sensitivity are relevant to study of migraine photophobia

“…More importantly however, because light stimuli used in PLR studies differ in intensity and duration (e.g. 200 ms for PLR versus 4 ms for ERG and VEP) from light stimuli used in ERG and VEP studies, it is difficult to interpret the Lobato- Rincon et al (2014) findings in the context of ours. In contrast, a brief review of existing literature-where photic stimuli were delivered as full-field (Ganzfeld) rather than a point light source-does not support the scenario that pupil constriction affected our ERG and VEP results.…”

“…If this were the case in our study, one would expect to find smallest pupillary constriction response to blue light, largest to green light and somewhere in between to red and amber lights. In support of this scenario, Dr Mahroo cites a study by Lobato-Rincon et al (2014), which shows that the amplitude and latency of pupil constriction in response to green light is larger than blue and red lights.…”

A Review of Pupillometry for Human-computer Interaction Studies

“…As already mentioned, age is a major factor in many parameters of the PLR and should be accounted for in all studies [14]. Older participants show decreased amplitude of response [21], increased latency and in some cases decreased velocity [20] as well.…”

“…One such study used [20] isoluminant (5 lux at the cornea) white, blue (450 nm), green (510 nm) and red (600 nm) light. They reported that the white and green light conditions had the greatest amplitude and shortest latency times.…”