Morjaria, Rupal; (2018) Impact of ocular disease on circadian rhythms and brain connectivity. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Investigation into the impact of ocular disease on sleep and mood has shown that in humans eyes have an important role, and that absence of eyes or interference with light reaching the retina can have deleterious effects. Light is the main zeitgeber ‘time-giver’ used by most species for the regulation of circadian rhythms and is detected by rods, cones and photosensitive retinal ganglion cells (pRGCs) in mammals. The aims of this research project were to investigate this from three different perspectives. Three prospective studies were undertaken. The first, studied the impact of ocular disease on the sleep/wake cycle in diabetic retinopathy (DR) and in bilateral anophthalmia. There was no significant difference found between the severity of DR and global sleep scores, however the acquired anophthalmic groups have significantly raised global sleep scores compared to controls and the congenital anophthalmic group. Both anophthalmic groups had varying sleep/wake cycles on their actograms depending on the lifestyle (independent of the urinary melatonin). All the anophthalmic participants showed a non 24 hour sleep-wake rhythm disorder after melatonin profiling. The second study investigates the evidence for the presence of extraocular circadian photoreceptors (EOCP) in participants with anophthalmia and sighted controls. Changes in brain activity using a functional MRI scan was assessed, when a bright white light is shining in different locations. This study did not reveal any evidence of EOCP.Finally, structural brain MRI differences in anophthalmic groups were investigated. While similar changes in structural reorganisation occur in all anophthalmic groups in the occipital cortex, the acquired anophthalmic groups show an inverse relation with the time since becoming anophthalmic and the volume of optic radiation and optic nerve volume. The acquired anophthalmic group did not show increase in hippocampal volume (memory areas) or in the precuneus (spatial navigation) contrast to the congenital anophthalmic groups.

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