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Pierre-Francois Isard, Simon Potier, Thomas Dulaurent, Marielle Mentek; Evaluation of photoreceptors and ipRGC responses in conscious black kite (Milvus migrans) using chromatic pupillometry. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5049.
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© ARVO (1962-2015); The Authors (2016-present)
Birds of prey are characterized by highly specified visual function and retinal structure, permitting for some of them the highest visual acuity among animal species. Increasing knowledge on raptors retinal structure raised from histologic studies, however little is known about the physiologic responses of the retinal cells, mainly due to invasive and poorly suitable available electrophysiologic tools. The goals of this study are 1) to evaluate the feasibility of chromatic pupillometry in conscious birds of prey, with the example of the black kite (Milvus migrans) 2) to describe pupil light reflex (PLR) associated with rods, cones and intrinsically photoreceptive retinal ganglion cells (ipRGC) stimulation in the adult black kite.
Twenty five black kites, non-chemically restrained, were tested during the experiment. Each bird underwent a complete ophthalmologic examination prior to PLR recording. After at least 10 min of dark adaptation, PLR was assessed in the right eye of each animal, using a commercially available chromatic pupil light reflex device (Pupil-LR, SIEM Bio-Médicale, Nimes, France). PLR was recorded under mesopic environment, in response to three successive 1-sec light stimulus: 1) blue light with low intensity (LB, 460 nm , 0.28 log cd/m2), 2) red light with high intensity (HR, 640 nm, 2.61 log cd/m2) and 3) blue light with high intensity (HB, 460 nm , 2.61 log cd/m2).
A total 88% of PLR recordings were classified as stable and used for the analysis. Baseline pupil diameter was similar before each stimulation (6.62 ± 1.05 mm). PLR was characterized by a significant higher latency during the LB stimulus (0.05 ± 0.02 sec) compared to HR and HB stimulus (0.03 ± 0.01 sec, p = 0.004). Maximal pupil contraction was significantly lower for LB stimulus (28.95 ± 8.34 %, p < 0.0001) compared to HR and HB (46.02 ± 6.63 % and 47.46 ± 5.2 % respectively). In accordance with the stimulation of ipRGC, a sustained PLR was observed after HB stimulus (% pupil diameter = 85.67 ± 5.81 %, p < 0.0001) compared to LB and HR stimuli (98.9 ± 2 %).
Chromatic pupillometry is a non-invasive and efficient method to assess photoreceptors and ipRGC function in the conscious black kite. PLR characteristics are strongly correlated with retinal anatomy and support the potency of this method for research or clinical purposes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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