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      The Pupillary Light Reflex in Idiopathic Intracranial Hypertension

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          Abstract

          Purpose

          To evaluate the effects of idiopathic intracranial hypertension (IIH) on rod-, cone-, and melanopsin-mediated pupillary light reflexes (PLRs).

          Methods

          Pupillary light reflexes elicited by full-field, brief-flash stimuli were recorded in 13 IIH patients and 13 normal controls. Subjects were dark-adapted for 10 minutes and the PLR was recorded in response to short-wavelength flashes (0.001 cd/m 2: rod condition; 450 cd/m 2: melanopsin condition). Subjects were then exposed to a rod-suppressing field and 10 cd/m 2 long-wavelength flashes were presented (cone condition). Pupillary light reflexes were quantified as the maximum transient constriction (rod and cone conditions) and the post-illumination pupil constriction (melanopsin condition), relative to the baseline pupil size. Diagnostic power was evaluated using receiver operating characteristic (ROC) analysis.

          Results

          The IIH patients had significantly smaller PLRs under the melanopsin ( P < 0.001) and rod ( P = 0.04) paradigms; a trend for reduced cone-mediated PLRs was also found ( P = 0.08). Receiver operating characteristic analysis indicated areas under the curves (AUC) of 0.83 (melanopsin-meditated; P = 0.001), 0.71 (rod-mediated; P = 0.07), and 0.77 (cone-mediated; P = 0.02). The AUC (0.90, P < 0.001), sensitivity (85%), and specificity (85%) were high for ROC analysis performed on the mean of the rod, cone, and melanopsin PLRs.

          Conclusions

          Pupillary light reflex reductions in IIH patients indicate compromised RGC function. PLR measurement, particularly under rod- and melanopsin-mediated conditions, may be a useful adjunct to standard clinical measures of visual function in IIH.

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          Most cited references 40

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          Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN.

          Human vision starts with the activation of rod photoreceptors in dim light and short (S)-, medium (M)-, and long (L)- wavelength-sensitive cone photoreceptors in daylight. Recently a parallel, non-rod, non-cone photoreceptive pathway, arising from a population of retinal ganglion cells, was discovered in nocturnal rodents. These ganglion cells express the putative photopigment melanopsin and by signalling gross changes in light intensity serve the subconscious, 'non-image-forming' functions of circadian photoentrainment and pupil constriction. Here we show an anatomically distinct population of 'giant', melanopsin-expressing ganglion cells in the primate retina that, in addition to being intrinsically photosensitive, are strongly activated by rods and cones, and display a rare, S-Off, (L + M)-On type of colour-opponent receptive field. The intrinsic, rod and (L + M) cone-derived light responses combine in these giant cells to signal irradiance over the full dynamic range of human vision. In accordance with cone-based colour opponency, the giant cells project to the lateral geniculate nucleus, the thalamic relay to primary visual cortex. Thus, in the diurnal trichromatic primate, 'non-image-forming' and conventional 'image-forming' retinal pathways are merged, and the melanopsin-based signal might contribute to conscious visual perception.
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            A novel human opsin in the inner retina.

            Here we report the identification of a novel human opsin, melanopsin, that is expressed in cells of the mammalian inner retina. The human melanopsin gene consists of 10 exons and is mapped to chromosome 10q22. This chromosomal localization and gene structure differs significantly from that of other human opsins that typically have four to seven exons. A survey of 26 anatomical sites indicates that, in humans, melanopsin is expressed only in the eye. In situ hybridization histochemistry shows that melanopsin expression is restricted to cells within the ganglion and amacrine cell layers of the primate and murine retinas. Notably, expression is not observed in retinal photoreceptor cells, the opsin-containing cells of the outer retina that initiate vision. The unique inner retinal localization of melanopsin suggests that it is not involved in image formation but rather may mediate nonvisual photoreceptive tasks, such as the regulation of circadian rhythms and the acute suppression of pineal melatonin. The anatomical distribution of melanopsin-positive retinal cells is similar to the pattern of cells known to project from the retina to the suprachiasmatic nuclei of the hypothalamus, a primary circadian pacemaker.
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              Diagnostic criteria for idiopathic intracranial hypertension.

              The syndrome of increased intracranial pressure without hydrocephalus or mass lesion and with normal CSF composition, previously referred to as pseudotumor cerebri, is a diagnosis of exclusion now termed idiopathic intracranial hypertension (IIH). Diagnostic criteria of this disorder have not been updated since the Modified Dandy Criteria were articulated in 1985. Since then, new developments, including advances in neuroimaging technology and recognition of additional secondary causes of intracranial hypertension, have further enhanced the ability to diagnose conditions that may mimic IIH. These factors are not addressed in the Modified Dandy Criteria. This report describes updated diagnostic criteria for IIH that may be used for routine patient management and for research purposes.
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                Author and article information

                Journal
                Invest Ophthalmol Vis Sci
                Invest. Ophthalmol. Vis. Sci
                iovs
                iovs
                iovs
                Investigative Ophthalmology & Visual Science
                The Association for Research in Vision and Ophthalmology
                0146-0404
                1552-5783
                4 January 2016
                January 2016
                : 57
                : 1
                : 23-29
                Affiliations
                [1 ]Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
                [2 ]Department of Neurology & Rehabilitation, University of Illinois at Chicago, Chicago, Illinois, United States
                [3 ]Department of Psychology, University of Illinois at Chicago, Chicago, Illinois, United States
                [4 ]Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States
                Author notes
                Correspondence: J. Jason McAnany, University of Illinois at Chicago, 1905 W. Taylor Street, Chicago, IL 60612, USA; jmcana1@ 123456uic.edu .
                Article
                iovs-57-01-03 IOVS-15-18181
                10.1167/iovs.15-18181
                4713014
                26746015

                This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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                Categories
                Eye Movements, Strabismus, Amblyopia and Neuro-Ophthalmology

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