title: Rhodopsin and Melanopsin Contributions to the Early Redilation Phase of the Post-Illumination Pupil Response (PIPR).
abstract: Melanopsin expressing intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) entirely control the post-illumination pupil response (PIPR) from 6 s post-stimulus to the plateau during redilation after light offset. However, the photoreceptor contributions to the early redilation phase of the PIPR (< 6 s post-stimulus) have not been reported. Here, we evaluated the photoreceptor contributions to the early phase PIPR (0.6 s to 5.0 s) by measuring the spectral sensitivity of the criterion PIPR amplitude in response to 1 s light pulses at five narrowband stimulus wavelengths (409, 464, 508, 531 and 592 nm). The retinal irradiance producing a criterion PIPR was normalised to the peak and fitted by either a single photopigment nomogram or the combined melanopsin and rhodopsin spectral nomograms with the +L+M cone photopic luminous efficiency (Vλ) function. We show that the PIPR spectral sensitivity at times ≥ 1.7 s after light offset is best described by the melanopsin nomogram. At times < 1.7 s, the peak PIPR sensitivity shifts to longer wavelengths (range: 482 to 498 nm) and is best described by the combined photoreceptor nomogram, with major contributions from melanopsin and rhodopsin. This first report of melanopsin and rhodopsin contributions to the early phase PIPR is in line with the electrophysiological findings of ipRGC and rod signalling after the cessation of light stimuli and provides a cut-off time for isolating photoreceptor specific function in healthy and diseased eyes.
authors.affiliation: Visual Science and Medical Retina Laboratories, Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.|School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.
authors.forename: Prakash
authors.initials: P
authors.lastname: Adhikari
authors.affiliation: Visual Science and Medical Retina Laboratories, Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.|School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.|Queensland Eye Institute, Brisbane, Queensland, Australia.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Feigl
authors.affiliation: Visual Science and Medical Retina Laboratories, Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.|School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Zele
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology / Q000528:radiation effects*; D012025:Reflex, Pupillary / Q000502:physiology / Q000528:radiation effects*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000528:radiation effects*; D012243:Rhodopsin / Q000502:physiology*; D017299:Rod Opsins / Q000502:physiology*; D013997:Time Factors; D000099210:Melanopsin
chemical_list: D012243:Rhodopsin; D017299:Rod Opsins; D000099210:Melanopsin