![]() 4, 11 – 15 Alternatively, the postillumination pupil response (PIPR) has been used to evaluate the loss of melanopic PLR in glaucoma. 10 Normal human melanopic PLR component has been estimated with the use of special stimulus and adaptation conditions. 7 In non-human primates, on the other hand, melanopic PLR has been isolated with the use of toxins that block transmission of signaling from photoreceptors to postreceptoral neurons. ![]() 4 Isolation of the melanopic PLR 9 in vivo without interference from outer retinal photoreceptors has been achieved in mice where phototransduction of rods and cones has been genetically abolished. 8 With high light levels, however, all ocular photoreceptors are activated, and signals from outer and inner retinal photoreceptors combine in a complex manner to drive the PLR. 6, 7 Since rods are by far the most sensitive among all of the PLR photoreceptors, rod-dominated PLRs can be recorded in dark-adapted normal human eyes illuminated homogeneously across the visual field with lights that are above rod threshold but below cone and ipRGC thresholds. 1, 2 Depending on the temporal and spectral properties of the light and ocular adaptation conditions, the normal PLR is driven by melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs), 3, 4 which constitute a small proportion of all RGCs, 5 as well as rod and cone photoreceptors of the outer retina. Steady-state pupil size and its dynamic changes are strongly influenced by the ambient light and previous light history through the pupillary light reflex (PLR). ![]()
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