A specialised light-sensing cell in the eye, called a melanopsin-based photosensitive retinal ganglion cell, is being studied for how it controls sleep, mood, and the eye’s own defences against light damage. This matters because eye diseases such as glaucoma, cataract, and age-related macular degeneration are known to disrupt sleep and mood, yet clinical ophthalmology currently has no guidelines for managing these non-visual consequences. The researchers have already built a large patient database linking specific eye conditions to sleep and mood problems. They are also investigating whether the melanopsin system protects the retina from light-induced damage—mice lacking the melanopsin gene fail to activate protective genes after light exposure. If successful, this work could lead to national evidence-based guidelines for ophthalmologists, helping to prevent the cascade of health problems—including cognitive decline, depression, and heart disease—that follow from disrupted sleep in people with eye disease. It could also reveal new ways to protect the retina from light damage. The project combines fundamental science on how the eye encodes light with direct clinical translation, aiming to improve quality of life for millions of patients.
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Our broad vision is to: Provide a detailed understanding of how melanopsin-based photosensitive retinal ganglion cells (pRGCs) encode and signal light information for the regulation of ocular, circadian and sleep physiology and to translate this knowledge into clinical and public understanding for the improvement of health. A seven-year programme of work is summarised in Figure 1. These aims align very closely with two of the Wellcome Trusts major challenges: (i) Understanding the brain; (ii ) Maximising the health benefits of genetics and genomics. Aim 1: Define the impact of ocular disease on human sleep/wake timing and mood. Despite the critical importance of the eye in regulating human circadian rhythms, sleep, alertness and mood [1], these critical behaviours are rarely addressed in clinical ophthalmology and specific guidelines relating to the disruption of these faculties in ocular disease are entirely lacking. To redress this omission, a Wellcome Trust Enhancement Aw ard allowed us to initiate such a study in January 2013. We have established the recruitment protocols and developed the infrastructure for both primary [2] and advanced [3] phenotyping of sleep and circadian abnormalities across a broad range of ocular diseases. As of June 2014 we have the following patient numbers recruited into the study: Cataract (n=961); Glaucoma (n=191); AMD (n=326); Diabetes II (n=446); Anophthalmia (n=12); RP (n=46). The results from the continuation of these studies wil l permit us to: -Build a comprehensive database linking specific ocular diseases, and disease states, to sleep and mood problems. -Establish which interventions are the most effective in improving these abnormal sleep states (see Aim 6). -Develop national evidence-based guidelines for clinical ophthalmology. We stress, disrupted sleep is closely linked to the added susceptibility of a range of co-morbid pathologies, including cognitive decline, depression, attentional failures, metabo lic and immune problems, and heart disease [4]. Thus ocular disease not only results in visual dysfunction but has the potential to inflict multiple additional pathologies, all of which can lead to major deficits in health and quality of life. Aim 2: Address the role of melanopsin in ocular light protection. The eye has several mechanisms to protect itself from light damage [5; 6], but the photopigment systems that activate these responses remain poorly defined. We reasoned that OPN4 may play an important role. Microarray studies were undertaken on the retinae of mice either lacking melanopsin (Opn4-/-) or wild-type controls (Opn4+/+) following light exposure. Multiple genes that normally protect the retina from light damage were highly up regulated in Opn4+/+ mice but this response was absent in Opn4-/- mice. Building upon these striking findings we will address: -Are Opn4-/- animals more susceptible to light-induced retinal damage? Following different light treatments the e ye/retina of Opn4-/- mice will be examined histologically and using TUNEL staining to detect DNA fragmentation and other markers of light-induced damage. -How is OPN4 mediating this protective effect? Light mediates an increase in retinal dopamine, which may or may not be mediated by OPN4 [7; 8]. We
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