Optometry and Vision Sciences - Theses
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ItemTowards improving the detection of diabetic retinal disease( 2023-08)Diabetic retinopathy is a visual complication of diabetes clinically diagnosed by the presence of visible microvascular lesions in the retina. Since the hallmarks of diabetic retinopathy are vascular in nature, the assumption is that the retinal microvasculature is the main disease casualty. However, the impact of diabetes on the retina is widespread, affecting multiple components within the retinal neurovascular unit. More recent evidence reveals that retinal neuron damage, which can be manifested as visual function deficits and degeneration of the retinal layers, occurs prior to classical diabetic microvascular features. The American Diabetes Association has acknowledged diabetic retinopathy as a neurovascular complication of diabetes (Solomon et al., 2017). Additionally, some groups have also proposed the term “diabetic retinal disease” instead of diabetic retinopathy, as the terminology of the former more comprehensively characterises any retinal change owing to diabetes (Abramoff et al., 2018; Sun et al., 2021). Although new research reinforces vascular retinopathy as a late consequence of diabetic retinal disease, visual acuity (which remains preserved until the end stage of the disease) continues to serve as the main functional outcome for diabetic retinopathy in clinical research. Clinical detection of diabetic vascular lesions associated with an increased risk for visual impairment is also the only management strategy available for individuals at the early stages of the disease. Screening for diabetic retinopathy via ophthalmoscopic inspection remains the mainstay of clinical optometric practice and is still recommended by authoritative guidelines. The cost for diabetic retinopathy screening programmes is significant as persons with diabetes are (1) often working age, (2) will have to undergo several screening eye examinations in their lifetime, and (3) left without any therapeutic options until their vision is close to being compromised. New clinical markers, especially those that are likely to herald vascular damage, have the potential to improve detection of diabetic retinal disease. Numerous studies across the years have revealed a range of visual functional deficits in individuals with diabetes. Advances in retinal imaging technology, notably optical coherence tomography (OCT), have revolutionised clinical diagnosis of several retinal diseases. In the context of diabetic retinal disease, progressive thinning of the retinal neural layer can be measured by OCT in some individuals without diabetic retinopathy, supporting the notion of retinal neurodegeneration. OCT-angiography (OCTA), an update of OCT, can also detect microvasculature changes prior to overt vascular retinopathy. The focus of this thesis will be on clinical assessments of diabetic retinal disease. This thesis explored functional and structural outcomes measures from novel psychophysical techniques as well as structural OCT and OCT-A that could predict future diabetic retinopathy. Altogether, this thesis highlights the need for comprehensive assessment of diabetic retinal disease, which has future implications for improving how clinicians screen for and manage those with diabetic retinopathy.