Assessing rod, cone and melanopsin contributions to human pupil flicker responses

Barrionuevo, Pablo A., Nicandro, Nathaniel , McAnany, J. Jason, Zele, Andrew J., Gamlin, Paul, & Cao, Dingcai (2014) Assessing rod, cone and melanopsin contributions to human pupil flicker responses. Investigative Ophthalmology & Visual Science, 55(2), pp. 719-727.

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Abstract

Purpose:

To determine the relative contributions of rods, cones and melanopsin to pupil responses in humans using temporal sinusoidal stimulation for light levels spanning the low mesopic to photopic range.

Methods:

A four-primary Ganzfeld photostimulator controlled flicker stimulations at seven light levels (-2.7 to 2 log cd/m2) and five frequencies (0.5 to 8Hz). Pupil diameter was measured using a high-resolution eyetracker. Three kinds of sinusoidal photoreceptor modulations were generated using silent substitution: 1) rod modulation, 2) cone modulation, and 3) combined rod and cone modulation in phase (Experiment 1) or phase shifted (Experiment 2) from a fixed rod phase. The melanopsin excitation was computed for each condition. A vector sum model was used to estimate the relative contribution of rods, cones and melanopsin to the pupil response.

Results:

From Experiment 1, the pupil frequency response peaked at 1Hz at two mesopic light levels for the three modulation conditions. Analyzing the rod-cone phase difference for the combined modulations (Experiment 2) identified a V-shaped response amplitude with a minimum between 135° and 180°. The pupil response phases increased as cone modulation phase increased. The pupil amplitude increased with increasing light level for cone and combined in-phase rod and cone modulation, but not for the rod modulation.

Conclusions:

These results demonstrate that cone- and rod-pathway contributions are more predominant than melanopsin contribution to the phasic pupil response. The combined rod, cone and melanopsin inputs to the phasic state of the pupil light reflex follow linear summation.

Impact and interest:

17 citations in Scopus
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20 citations in Web of Science®

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ID Code: 78832
Item Type: Journal Article
Refereed: Yes
Keywords: melanopsin, flicker, silent-substitution, pupil light reflex
DOI: 10.1167/iovs.13-13252
ISSN: 0146-0404
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300) > Vision Science (111303)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Optometry & Vision Science
Funding:
Copyright Owner: Copyright 2014 Association for Research in Vision and Ophthalmology
Deposited On: 20 Nov 2014 23:22
Last Modified: 24 Nov 2014 18:01

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