Abstract
Purpose:
The identification of melanopsin-expressed ganglion cells (mRGCs) exposes extra pathways of visual system beyond conventional image-forming perceptions. The heavy loss of retinal ganglion cells (including mRGCs in two eyes) in late-stage retinal diseases such as retinitis pigmentosa (RP), glaucoma will lead to the mRGCs-related symptoms, especially insomnia and depression.
Methods:
56 patients with advanced RP, or late-stage glaucoma in both eyes were explored. The visual field examinations were used to define late-stages of these diseases, indicating the heavy loss of retinal ganglion cells and mRGCs in two eyes. The mRGCs-related symptoms including insomnia, photophobia, depression were collected and analyzed among these patients. The thickness of retinal ganglion cell layer was measured as another indicative parameter of retinal ganglion cells and mRGCs with OCT scanning. The pupillary diameters under resting condition and light stimuli showed the function of remained mRGCs.
Results:
As two eyes with retinal diseases approached to heavy loss of RGCs as well as mRGCs according to OCT scanning and pupillary diameters, the mRGCs-related symptoms including insomnia, photophobia, depression appeared in most patients (47/56). This matched the heavy loss of peripheral visual field and the thinning of retinal ganglion cell layer in both eyes. Some patients had no these symptoms, whose OCT scanning showed the remained retinal ganglion cell layer in one or two eyes even with the heavily damaged visual fields from patients with RP (7). They remained sensitive to the day-night cycle. Photophobia and lacrimation from light stimuli did not appear in these patients. Pupillary light responses exactly matched the loss of retinal ganglion cells and mRGCs in two eyes.
Conclusions:
mRGCs deal with the long-term temporal sense of visual system to entrain the intrinsic day-night cycle in human body, which symptomized as insomnia and depression in the late stage of RP and glaucoma. The symptoms such as dilated pupil, photophobia and lacrimation could be explained by damaged short-term temporal signals of mRGCs.