Optometry and Vision Sciences - Theses

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    Towards improving the detection of diabetic retinal disease
    Tang, Vanessa Thien Sze ( 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.
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    The role of home monitoring in chronic eye disease using smart devices.
    Prea, Selwyn Marc ( 2023-03)
    Chronic eye disease affects millions of people worldwide and requires ongoing specialist care. Ever-increasing patient numbers has created pressure on the healthcare system, an issue that has been intensified by the COVID-19 pandemic. There is a pressing need to develop new models of eyecare to prevent vision loss. Home monitoring (HM) of vision in-between scheduled clinical visits could help prioritise valuable hospital chair time to those with the highest risk. Smart devices, such as desktops, laptops, tablets, and smartphones are ubiquitous in the community making them an ideal platform for HM due to familiarity of use. Most older individuals use smart devices to access the internet and it is this age group that is at a higher risk for developing chronic eye disease. This thesis considers the role of HM with the Melbourne Rapid Fields (MRF) vision testing application (for the Apple iPad) in the context of two common chronic eye diseases; glaucoma and age-related macular degeneration (AMD). MRF is new technology without a proven clinical record. Chapter 2 reports the clinical application of MRF as a routine and regular test of visual field (VF) by comparing 2-monthly VF testing to that found using the Humphrey Field Analyzer (HFA) for glaucoma patients in-clinic. We find the MRF has a strong correlation to the HFA with excellent medium-term repeatability (6-month period). This means that MRF can produce the same outcomes as the HFA when performed under supervision in the clinic. Chapters 3 and 4 apply the MRF to a weekly HM regime where participants tested themselves at home under application generated audio instructions and in the absence of clinical supervision. HM was undertaken for 12-months, and all participants had access to a clinical assistant who could be contacted to resolve technical difficulties. Chapter 3 finds that glaucoma participants had an uptake of 88% to HM and a weekly compliance of 72% with same-day reminders. A strong correlation was observed between the MRF at-home and the HFA in-clinic, and progression was detected in two participants using MRF home monitoring. Chapter 5 reports the HM uptake to be 85% in patients with intermediate AMD (iAMD) with a weekly compliance of 61% in the absence of reminders. Here, the HM included visual acuity as well as macula visual field sensitivity. Good correlation was observed between MRF and clinical measures with the Early Treatment Diabetic Research Study (ETDRS) letter chart and the Macular Integrity Assessment (MAIA) microperimeter. The overall findings of this thesis are that patients with chronic eye disease are receptive to the concept of HM with smart devices due to promising uptake. The finding of moderate compliance to weekly testing can be considered as a reduced number of tests received from home but, can still provide valuable information for clinical decision making. A survey of participant perceptions reveals that the MRF is easy to use and more comfortable than clinical perimeters. Larger, randomised, clinical trials are required to expose the true ability of MRF to detecting progression before it can be implemented as a new model of patient eye care.
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    Neuroregenerative and anti-inflammatory effects of decorin on the injured cornea
    Wu, Mengliang ( 2022)
    The cornea is densely innervated by sensory nerves that responds to noxious stimuli and produces neurotrophic factors to maintain ocular surface homeostasis. However, corneal sensory nerves are susceptible to damage from a range of ocular and systemic conditions, including dry eye disease, corneal infection, trauma, surgical procedures and diabetes mellitus. Despite corneal nerve impairment being a key pathophysiologic factor in many ocular surface diseases, there are few effective therapeutic approaches to promote corneal nerve regeneration. Decorin is an extracellular matrix protein that belongs to a family of small leucine-rich proteoglycans. Decorin interacts with different signaling molecules to regulate various cellular processes including collagen fibrillogenesis, fibrosis, inflammation and axon growth. There is evidence that decorin is of great potential as a therapeutic for treating spinal cord injury to suppress the formation of a glial scar and promote axon growth. Here, it is hypothesized that exogenous decorin may provide therapeutic benefits in peripheral nerve damage in corneal neuropathy. This thesis aims to explore the neuroregenerative and anti-inflammatory effects of decorin on the injured cornea and to verify its therapeutic potential to restore corneal homeostasis after corneal nerve injury. To assess this, corneal nerve damage was modelled in mice by direct abrasion of the central epithelium. Decorin or vehicle was applied topically after the injury and wholemount immunofluorescence staining was used to assess corneal sensory nerves and immune cell densities. Topical decorin treatment was associated with a higher density of corneal sensory nerves, relative to topical vehicle (control) treatment. This neuroregenerative effect of decorin was not observed in Cx3cr1gfp/gfp mice that spontaneously lack corneal epithelial dendritic cells (DCs), indicating that decorin-induced corneal nerve regeneration depends on the presence of DCs. In addition, topical decorin induced a higher density of DCs after six hours, and a lower density of macrophages at one week post-injury, supporting a role for decorin in modulating corneal immune responses. To further investigate the immunomodulatory effect of decorin during corneal wound healing, the same model was used to evaluate the temporal changes to corneal immune cells at multiple timepoints, including 12 hours, 24 hours, 3 days and 5 days post-injury. After topical decorin application, a higher density of corneal epithelial DCs and a lower density of infiltrating neutrophils were observed at 24 hours after injury. The decorin-induced lower neutrophil density was also DC-dependent. Consistent with the previous study, corneal stromal macrophage density was lower and corneal nerve density was higher in decorin-treated eyes compared to saline-treated controls. Interestingly, a higher percentage of the injured corneal area was re-epithelialized in decorin-treated eyes at 12 hours post-injury. These findings confirmed the neuroregenerative effect of decorin and demonstrated a distinctive pattern of temporal dynamics of corneal immune cells that were modulated by topical decorin. These effects of topical decorin on the injured cornea were associated with altered expression of transforming growth factor beta and chondroitin sulfate proteoglycan 4 signaling mRNA. In addition to evaluating an acute epithelial injury, repeated exposure to a corneal neuro-toxic stimulus was also considered, as this is not uncommon in clinical settings (e.g., in patients with long-term use of preservative-containing eye drops). Therefore, the therapeutic effects of decorin were also investigated in an animal model of chemical-induced corneal neuropathy, with repeated topical exposure to a common preservative benzalkonium chloride (BAK). Topical decorin treatment was also applied during a one-week period of daily BAK exposure. This study showed that decorin-treated eyes had less corneal neutrophil infiltration and a lower density of macrophages, accompanied by a higher density of corneal sensory nerves. In addition, corneal nerve density was negatively correlated with macrophage and neutrophil density, indicating that alterations to corneal immune cells induced by decorin may contribute to a higher density of sensory nerves. Together, these findings advance understanding of the relationship between corneal sensory nerves and immune cells, and more importantly, provide evidence for the therapeutic potential of topical decorin in conditions characterized by corneal nerve damage with local inflammation.
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    Increased spatial sampling in automated static visual field testing
    Thudupathi Muthusamy, Vasanth ( 2022)
    The overarching aim of this thesis was to explore various approaches to increase spatial sampling in clinical static automated perimetry (SAP) testing. The motivation for this aim arose from observations that clinically implemented SAP methods use a “one-test-fits-all” fixed test pattern, despite the fact that patterns of visual field loss vary markedly between individuals. This thesis explored whether it is possible to increase spatial sampling without increasing test duration, and the pros and cons of such as approach. To approach this problem, this thesis engaged a range of methods, including direct experimental work with patients, survey research with healthcare consumers, and explored the opinions of expert clinicians. The Australian Reduced Range Extended Spatial Test (ARREST) is a new perimetric approach that has been shown to increase spatial sampling individually without increasing the test time. ARREST has previously been developed and evaluated using computer simulations. The first experiment in this thesis (Chapter 3) evaluated the feasibility and performance of the ARREST approach in testing people with established visual field loss. Chapter 4 in this thesis investigated patients’ subjective experience with current SAP testing using a mixed-method survey and asked their preferences and priorities for future perimetric developments. The final experiment in this thesis (Chapter 5) explored potential alternative methods for a glaucoma-specific ARREST approach by utilising clinically available information such as clinicians’ views and data from OCT imaging. Taken together, the results of these experiments demonstrate that increasing spatial sampling without increasing test duration is feasible with the ARREST approach. Furthermore, patients report that they would prefer tests that produce more information about their vision. In order to gain more information about their vision, patients also report being willing to perform more visual field tests and increase the frequency of visits for testing. The ARREST approach is currently agnostic to disease-specific needs hence this thesis also explored other clinically available information that might potentially be useful for stimulus placement for a glaucoma-specific ARREST approach. The results from the final experiment demonstrate that clinical experts vary significantly in their choice of stimulus locations to prioritise for further testing, but tend to favour placement in areas important for quality of life. Overall, this thesis provides possible methods for increasing spatial sampling without increasing test duration and demonstrates the importance of considering user and consumer input in the design of perimetric procedures.
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    Mapping the Parafoveal Capillary Network and Its Flow Characteristics in Healthy Eyes
    Neriyanuri, Srividya ( 2022)
    Capillary blood flow plays an essential role in the nourishment and maintenance of healthy neural tissue while, in disease, altered capillary flow patterns form the earliest signs of diabetic vasculopathy and are implicated in other major conditions including stroke and dementia. Despite its obvious importance, the difficult-to-meet demands of high spatial and temporal imaging resolution have hitherto limited detailed characterisation of how blood flows through normal capillary networks to maintain healthy retinal structure and function. In this thesis, capillary flow characteristics were studied in the central retina of three healthy young individuals using an adaptive optics ophthalmoscope to provide the required cellular-level spatial resolution, combined with fast frame rates (200-300 frames/second) adequate to capture the single-file flow of red blood cells in capillaries over the course of about 3 seconds. In the first part of the thesis, an automated kymograph method was validated against manual tracking of single red blood cells over successive movie frames for the measurement of instantaneous flow velocities. The automated method proved much faster, and arguments are presented to demonstrate its superior accuracy and robustness, particularly for vessels in which manual tracking is challenging due to high flow speeds. In the second part of the thesis, using the validated kymography approach, velocities were estimated contemporaneously from many neighbouring vessels of the parafoveal capillary network for each subject. Our findings show that capillaries universally exhibit a pulsatile flow pattern with alternating peaks and troughs in velocity with every heartbeat. A high degree of inter-vessel variability over a range of flow parameters (such as the peak, trough velocities, pulsatility, abruptness and peaktime), within a single subject and even within each retinal field, was `noted. This variability could not be explained by “local” vessel factors such as the vessel diameter, tortuosity, vessel length, linear cell density and hematocrit of the vessel. However, within a vessel, a moderate relation between velocities and hematocrit was noted, suggesting a redistribution of plasma between cells with changes in flow. Given the failure of local vessel factors to explain flow variability, the final part of the thesis explored associations between flow and capillary network variables including vessel depth, branch order, and distance from the feeding arteriole of a network. A detailed network analysis to establish the vessel connections and classifications are also presented. Most of the vessels studied were of terminal capillary type with collecting and supplying junctions on either side. Nearly 47 % of the upstream and downstream vessel junctions were amenable to fitting with a model of relative branch diameters based on Murray’s Law, with only a few adhering to modelled expectations. However, a key parameter of the model (the junction exponent) was found to be inversely related to the average velocity and trough velocity in downstream vessels. Cellular flow velocities were also moderately correlated with the length of vessel segments, and with distance to the upstream “feeding” arteriole. In summary, this thesis presents a validated method for studying retinal capillary flow characteristics in normal subjects and provides insights on flow variability within individual vascular networks.
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    Measuring central visual field loss using visual stimuli with natural scene statistics
    Srinivasan, Rekha ( 2021)
    Routine visual field assessments are performed using static automated perimetry that measures contrast detection performance for white luminance increment targets presented on a uniform luminance background. While offering a standardised measure of the visual field, such clinical visual field tests are not representative of natural viewing conditions. Previous studies show that some visual field defects are detectable via visual search behaviour analysis; for example, when watching a video or performing daily living tasks. Such measurements of performance using visual stimuli representing everyday tasks can provide information regarding how people with visual field loss perform day to day activities, but due to widely varying visual content, it is difficult to predict a generalised explanation of performance with these tasks to create a widely applicable screening tool. This thesis aimed to develop a method for detecting central visual field loss by measuring the number of fixations to find targets on a background with spatial frequency content similar to natural scenes (referred to as 1/f noise). An advantage of this proposed approach is the existence of an established theoretical framework [Najemnik, J., & Geisler, W.S. (2005), Nature, 434(7031), 387-391] that links the detectability of targets within an image to the number of fixations required by a Bayesian ideal observer to find the targets. The stimulus and behavioural methods used in this thesis were chosen to be consistent with those used to validate the Bayesian ideal observer model. Four experiments were explored in this thesis that stepped through creating the screening protocol for detecting central visual loss. In the first step, Experiment One computationally assessed the suitability of using similar stimuli and behavioural methods as Najemnik and Geisler (2005) to detect field loss. Experiment Two evaluated the need for an age-matched normative limit for setting the contrast of the target for the screening protocol using such a method. Experiment Three determined the requirement of age-matched normative data for the number of the fixations to find the targets on the 1/f noise background, the outcome measure for the screening protocol. The outcomes from Experiment One to Three were then applied to Experiment Four that developed a prototype test for detecting central visual field loss by measuring the number of fixations required to search for a target on a 1/f noise background. This experiment also tested if the developed prototype was able to detect central visual field loss in a group of glaucoma participants. The prototype test demonstrated 85% sensitivity for a fixed specificity of 95.2% in screening abnormal areas in central vision in the glaucoma group. The task requirements of the screening protocol were designed to be representative of natural visual environments and to be intuitive for participants to perform the test. While the prototype test was tested in participants with glaucoma, the developed methods in this experiment are designed to generalise to any form of central visual field loss.
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    Functional and structural adaptations to ageing and acute intraocular pressure elevation in mouse retina
    Lee, Pei Ying ( 2021)
    In response to stress, neurons undergo a series of adaptations, which include changes to their synapses, dendrites and eventually axons and cell bodies. One might presume that such stress responses help to prevent cell death, providing a window of time where recovery remains possible. As glaucoma is a disease of the ageing, it may be reasonable to suggest that older eyes somehow show poorer adaptations to stress or have reduced intrinsic abilities to detect pressure changes in their environment (e.g., via mechanosensitive channels such as transient receptor potential (TRP) channels), and thus less capacity to recover. Whilst support for these ideas can be gleaned from a range of studies in other systems including the central nervous system, there has been less work in this area in the context of glaucoma. The overarching aim of the thesis is to understand the functional and structural adaptations that occur in normal ageing, and to consider if such age-related changes modify the way that retinal ganglion cells (RGCs) cope with intraocular pressure (IOP) elevation. Using the mouse as a platform, it was possible to show that in normal ageing, there was a relative preservation of ganglion cell function despite an age-related decline in outer retinal responses. Age-related inner retinal functional adaptations were associated with increases in bipolar cell sensitivity to light and changes to RGC dendritic complexity. Ageing was also associated with slower recovery from a short period of controlled IOP elevation. IOP elevation resulted in smaller ON RGCs in both young and older mice. Importantly, analysis of RGC morphology showed that better functional recovery in younger eyes was associated with adaptations in OFF RGC dendrites, which was not observed in older eyes. The absence of RGC morphological adaptations following IOP elevation may account for the delayed recovery in older eyes. Furthermore, better ganglion cell functional recovery in younger eyes was also associated with TRPV4 upregulation in the ganglion cell layer. In contrast, there was TRPV4 downregulation in older eyes. Consistent with the importance of TRPV4 upregulation for recovery, inhibiting TRPV4 further worsened recovery in older eyes. This work advances our understanding of age-related functional and structural adaptations, providing insights into how normal function is maintained in ageing, with potential negative impacts on the capacity for RGCs to recover from IOP elevation.
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    Computer vision syndrome and blue light blocking lenses: closing the evidence gap
    Hari Singh, Sumeer Singh ( 2021)
    Computer use is ubiquitous in this digital era and the majority of computer users report eye strain, often referred to as “computer vision syndrome” (CVS) or “digital eye strain”. The most common ocular symptoms associated with CVS are visual fatigue, followed by blurred vision, and dry eyes; these symptoms can occur immediately, or after several hours of computer use. Recently, blue light has been hypothesised to be a cause of CVS and blue light-blocking lenses were introduced with an aim to alleviate symptoms of CVS. However, there is a dearth of evidence from high quality clinical trials to support the efficacy of these lenses, and the potential mechanism of action of blue light-blocking lenses for modifying CVS remains unknown. The major aim of this thesis was to close the evidence gap in relation to the use and applicability of blue light-blocking spectacle lenses for alleviating eye strain associated with CVS. First, a systematic review was conducted to investigate the efficacy and safety of different interventions for treating CVS (Chapter 2). Randomised controlled trials investigating any intervention for managing signs or symptoms of CVS were identified, appraised for risk of bias, and synthesised. A range of interventions - including optical aids, oral supplements, complementary medicines, artificial tears, environmental modifications, yoga, and rest breaks - were identified. For the risk of bias assessment, the three domains that were judged to have the highest risks of bias in the included studies were performance bias, detection bias, and industry sponsorship bias. This systematic review found, with moderate certainty, that oral omega-3 fatty acid supplementation for 45 days improved symptoms of dry eyes in computer users compared to placebo. This review also found with low certainty, that oral berry extract supplementation for 8-12 weeks improved symptoms of visual fatigue and dry eyes, compared to placebo. The studies presented in Chapter 3 and 4 investigated the knowledge and self-reported practice patterns of Australian optometrists and ophthalmologists towards prescribing blue light-blocking ophthalmic lenses. In the optometrist’s survey, three in four respondents indicated prescribing blue light blocking lenses in their clinical practice. Forty-four percent of respondents considered daily environmental exposure to blue light as a potential cause of retinal damage, and approximately one in two respondents thought blue light emitted from computer screens was an important factor in causing CVS. The two main sources of information used by the respondents to guide their practice were conference presentations and manufacturer product information. In the ophthalmologist’s survey, 88% of respondents were cataract surgeons, of whom approximately half indicated recommending blue light blocking intraocular lenses to their patients. About one in four ophthalmologists considered daily environmental exposure to blue light to cause retinal damage. Similarly, 19% of respondents considered blue light emitted from computer screens to be a cause of CVS. The two main sources of information used by ophthalmologists to guide their clinical decision-making were published research papers and conference presentations. Finally, a double-masked, randomised controlled trial (RCT) was conducted to evaluate the efficacy and safety of blue light-blocking spectacles for reducing symptoms and clinical signs of CVS (Chapter 5). A novel aspect of the study design involved a randomisation step to modulate clinical advocacy of the intervention, whereby the investigator did/did not present the assigned intervention in a positive light. We found that blue light-blocking spectacle lenses did not modulate key signs or symptoms of eye strain associated with computer use, relative to standard (clear) lenses, and the relative advocacy of the clinician had no bearing on the clinical outcome. The work presented in this thesis advances our scientific understanding, and broadens the evidence base, relating to the management of CVS, and the current clinical practice behaviours of Australian optometrist and ophthalmologists towards prescribing blue light-blocking ophthalmic products. It provides evidence that blue light-blocking spectacle lenses do not reduce computer-induced eye strain relative to clear lenses, irrespective of whether or not they are advocated for by a clinician. Overall, findings from this thesis will contribute towards informing clinical guidelines that will assist practitioners with making evidence-based clinical decisions when treating CVS.
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    Visual search and visual performance in infantile nystagmus syndrome
    Dai, Bing ( 2020)
    Abstract Infantile nystagmus syndrome (INS) is an involuntary ocular motor oscillation, which presents at or near birth and persists throughout life. The nystagmus intensity and visual acuity in INS may vary with gaze angle. The gaze with minimal nystagmus intensity and better visual performance is known as the null position. Nearly all the research on INS focused on visual acuity and the time needed to get the eyes onto the desired target (i.e., target acquisition time). In daily routines, we are constantly presented with search tasks that require us to find a target among distracters or tracking tasks where we need to identify moving objects and to estimate their speed of motion. These real-life visual activities entail complex visual functions, such as visual search and motion perception. However, research on INS and these visual functions is limited. Thus, this study aims to investigate how individuals with INS perform, compared with controls, when carrying out visual search tasks and motion perception tasks. Particularly, the study also aims to assess how the null position affects their visual performance. For visual search, two search conditions were presented: conjunction search and feature search. Search time and accuracy were used to assess visual search performance. For motion perception, three tasks were performed: coherent motion, velocity discrimination, and biological motion. Motion coherence thresholds, discrimination thresholds, and accuracy were measured for the three tasks, respectively. In visual search tasks, INS subjects showed poorer search performance, with longer search times compared to controls in both conjunction and feature search. No difference in accuracy between INS and control subjects was found. The null position did not affect the visual search performance in INS. In coherent motion and velocity discrimination tasks, INS subjects showed poorer performance, with elevated motion coherence and discrimination thresholds compared with controls. A positive null position effect was found only in velocity discrimination. In the biological motion task, no difference in accuracy between INS subjects and controls was found. In summary, visual search, coherent motion, and velocity discrimination were impaired in INS subjects, with the null position having a positive effect in velocity discrimination. However, biological motion perception was not affected by INS. Findings from this study could assist us in understanding of how INS actually affects the daily activities of patients, and aid us in developing new clinical visual function assessment for INS.
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    Central and peripheral motion perception in healthy older adults and its potential relevance to driving
    Sepulveda Ulloa, Juan Alejandro ( 2021)
    Aging of the population is a common phenomenon in many countries. This increase in the number of older individuals consequently implies an increase in the number of older drivers. Older adults have changes to vision that could potentially influence driving behavior, as visual information is the predominant sensory input for operating a motor vehicle. One visual function that is potentially relevant for driving performance is motion perception, as both the motor vehicle and the surroundings are in motion. This project explored differences to motion perception between older and younger adults and considered in the applied context of driving. Experiment One explored the differences in performance of healthy older and younger adults on different aspects of motion perception under daylight viewing conditions. A battery of seven psychophysical motion perception tasks was applied to a cohort of participants belonging to two age groups (older and younger adults). Motion perception was also studied comparing central and peripheral vision. This experiment demonstrated that older adults had different results to their younger counterparts for some aspects of motion perception. In addition, for most of the tasks, the effects of aging were similar in central and peripheral vision. In Experiments Two and Three, four motion perception tasks were selected from the battery of tasks used in Experiment One to further test under viewing conditions that are commonly described as problematic by older drivers. These conditions included vision at mesopic light levels, such as those found during nighttime driving (Experiment Two) and driving under headlight glare similar to that of oncoming cars (Experiment Three). These two viewing conditions were simulated in a laboratory-based testing procedure. The results showed that thresholds were in general poorer under low light levels in both age groups. Experiment Three demonstrated that the presence of a continuous glare source simulating car headlights did not impact performance on the selected motion perception tasks. Experiment Four explored the relationship between motion perception and the measurement of the ability to predict potential traffic hazards in a computerized video test (the hazard perception test). The results of this experiment showed that two motion perception tasks (Dmin and motion contrast) were statistically related to the scores in the hazard perception test, and better predicted performance than measurements of visual acuity. This thesis, therefore, contributed to the knowledge of how aging impacts different components of motion perception, not only under photopic viewing conditions, but also under mesopic light levels and under simulated glare. This thesis demonstrated that some motion perception tasks clearly distinguished between age groups (Dmin, motion contrast and biological motion), but these group differences were absent for other tasks (global motion coherence). In addition, some motion perception tasks presented a wide range of interindividual differences in performance, suggesting that aging is a very individual process that cannot be assumed from chronological age.