Dr. Fishman’s comments: Light sensitivity is a very important symptom that occurs in a variety of ocular diseases including dry eye disease. Dr. Galor has done truly pioneering work in this area and has written many papers on this topic. At FishmanVision, Dr. Fishman is also been conducting research in this area (see ARVO poster on the novel use of the Ilux device to measure severity of dry eye disease) working on new devices to both diagnose and treat photophobia from dry eye disease.
“What can photophobia tell us about dry eye?” by Dr. Galor et al.
Expert Rev Ophthalmol. 2016; 11(5): 321–324.
Highlights from this terrific editorial: Directly from their paper:
Photophobia and dry eye. Photophobia, or an abnormal experience of pain to light, is a frequent complaint in patients with sensations of ocular dryness. This editorial will review potential pathways of photo- phobia and discuss the possibility that its presence is suggestive of central sensitization as a component of dry eye (DE). Potential approaches to the treatment of central sensitization in DE and ways to address photophobia will also be discussed.
Pathways of photophobia. The trigeminal nerve and its nuclei (the nucleus caudalis in particular ) arise as obvious unifying culprits that can tie in photophobia and DE. The V1 distribution of the trigeminal nerve supplies nociceptive innervation to the ocular and orbi- tal structures as well as the meninges.
Other circuits originate from light sensing but not image- forming pathways, and this may explain the fact that even blind patients may experience photophobia . These originate from intrinsically photosensitive retinal ganglion cells (IPRGCs), with melanopsin rather than rhodopsin as photopigment. Melanopsin responds maximally to light at a wavelength of 480 nm. In humans, only a minority (0.2–0.8%) of ganglion cells are intrinsically photosensitive
Addressing photophobia in DE may require some additional considerations. First, the use of sunglasses indoors should be strongly discouraged. Wearing dark glasses indoors causes dark-adaption and only makes light sensitivity worse. Instead, tinted lenses, such as FL-41 (which blocks light at 480 nm; the wavelength at which IPRGCs are maximally sensitive) have been shown to improve light sensitivity in a variety of clinical situa- tions, including migraine and blepharospasm.