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Thanasis Panorgias, Danielle Lee, Katie Silva, David Borsook, Eric Alan Moulton; Pulvinar activation in a case of congenital idiopathic photophobia. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5302.
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© ARVO (1962-2015); The Authors (2016-present)
Numerous pathologies can contribute to photophobia. Photophobia may be triggered through melanopsin pathways (non-image forming), rod and cone pathways (image-forming), or some combination of the two. In this case report, we evaluated a 39 year old female with congenital idiopathic photophobia with functional magnetic resonance imaging (fMRI).
We tested the patient by presenting visual stimuli in an event-related fMRI experiment using a Siemens 3 Tesla TIM Trio. The protocol consisted of a stimulus that triggered the patient's symptoms (SYMPT), a stimulus that did not elicit any symptoms (ASYMPT), and a baseline that featured a black screen with a fixation cross. The SYMPT and ASYMPT stimuli were checkerboards with squares that each subtended 0.5 degrees of visual angle, generating a spatial frequency of 1 cycle per degree of visual angle and reversing at 7 Hz. The SYMPT stimulus consisted of white and blue and the ASYMPT stimulus consisted of white and red checks. Each stimulus was presented in 6-second blocks. Functional imaging datasets were processed and analyzed using the General Linear Model implemented by FSL (FMRIB's Software Library). Z-statistic images were thresholded using clusters determined by Z > 3.1 and a (corrected) cluster significance threshold of P=0.05.
The subject rated the SYMPT blue checkerboard as 2/10 for pain intensity and 6/10 for unpleasantness; she rated the ASYMPT red checkerboard as 0/10 for pain intensity and 0/10 for unpleasantness. Both SYMPT and ASYMPT conditions produced robust cortical activation, particularly in visual cortices. Activation in bilateral pulvinar nuclei was significantly greater with SYMPT than ASYMPT stimulation.
Pulvinar thalamic nuclei are associated with the melanopsin intrinsic photosensitive retinal ganglion cell (ipRGC) pathway. Their activation is consistent with the patient’s report that blue light differentially evoked photophobia. This appears to be the first demonstration of functional activation of the ipRGC pathway during photophobia in a patient.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Pulvinar nuclei were significantly more activated with the photophobia-evoking stimulus than control. Visual cortex was significantly activated in response to SYMPT (blue) and ASYMPT (red). Green indicates voxels significant for the SYMPT>ASYMPT contrast.
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