Connections between intrinsically photosensitive retinal ganglion cells and TBI symptoms

Abstract

The majority of traumatic brain injury (TBI) patients are classified as having a mild traumatic brain injury (mTBI). Despite being categorized as mild, these individuals report ongoing and complex symptoms, which negatively affects their ability to complete activities of daily living and overall quality of life. Some of the major symptoms include anxiety, depression, sleep problems, headaches, light sensitivity, and difficulty reading. The root cause for these symptoms is under investigation by many in the field. Interestingly, several of these symptoms such as headaches, ocular pain, light-sensitivity, and sleep disturbances may overlap and share underlying circuitry influenced by the intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells are light-sensing, but non-image forming, and they influence corneal function, pupillary constriction, and circadian rhythm. In this review, we discuss these symptoms and propose a role of the ipRGCs as at least one underlying and unifying cause for such symptomology.

Association of eye strain with dry eye and retinal thickness

“…Further, ipRGC-driven light sensitivity may be relieved with short wavelength light filtering eyewear to block blue-light and reduce light scattering [23][24][25]. Our previous investigation indicated GCC thickness was positively correlated with eye strain [11] and our hypothesis of ipRGC-associated eye strain is supported by numerous other investigations [26][27][28][29][30][31].…”

“…IpRGCs in the GCC may be associated with eye strain that causes discomfort or pain. This could be evoked through the trigeminal circuit after receiving short wavelength light emitted from lighting and displays [26][27][28][29][30][31]. Blue-light filtering eyewear may be effective for ocular symptoms related to ipRGC activation [23][24][25], however, it should be noted that sensitivity to light may depend on age, race and genetic factors [41,42] and blue-light filtering does not work in certain populations.…”

Inflammatory Regulation of CNS Barriers After Traumatic Brain Injury: A Tale Directed by Interleukin-1

“…While many TBI-induced visual deficits originate within the brain stem and visual cortex, significant changes occur to the visual system's peripheral portions, including the blood-retinal barrier (162). The retinal ganglion cellsresponsible for sensation of light and the formation of the optic nerveare linked to common post-TBI symptoms including dry eye, headache, and sleep issues (163). TBI causes cell death and thinning of the retinal ganglion cell layer, including apoptosis of the retinal ganglion cells (160,164,165).…”