Vision in the Environment, Work & Sport (VIEWS)
Research by this group is concerned with the clinical study of vision in health, ageing and disease. Work focuses on the topics that are of major relevance and impact within society.
Locomotor strategies are planned using information acquired by intermittent visual sampling of the environment, which means the visual system is free to attend to other things. This highlights that where and when we look are key factors in our ability to safely negotiate changing terrains. It also highlights that visual impairment that results in impoverished information about the environment may lead to the adoption of unsafe locomotion strategies.
How is landing behaviour affected by visual impairment when stepping down?
To understand what, where and how different aspects of visual (and other sensory) information is used to regulate locomotion and posture in various environments and ambient conditions.
- How correctable visual impairment such as refractive blur and cataract effects balance control and movement strategy during stair negotiation
- How multifocal spectacle use effects gait over obstacles and/or during transition to a new level
- How the removal of binocular vision effects movement planning and control
- What peripheral versus central cues are used to plan and control movement
Multifocal lens wearers are twice as likely to fall as single vision lens wearers. This is likely to be because low level objects are out of focus when viewed though the intermediate or near addition part of lens.
In the UK over 2m falls each year result in hospital treatment. Of these, almost 10% of cases are linked to visual impairment, with the majority being elderly individuals 65 yrs and above. It is estimated that up to 80% of this visual impairment is correctable via refractive correction (40%) or cataract removal (37%). Although it is known that visual impairment is a risk factor for falls, little is known about how visual impairment affects postural stability and obstacle & step/stair negotiation. Even when vision is optimally corrected, the use of multifocal spectacles has been linked to increased risk of falls.
Amblyopia is a developmental disorder of vision in which there is reduced visual function despite full optical correction and the absence of pathology.
Our work in amblyopia has the following aims:
- To understanding the precise nature of the amblyopic visual deficit
- To investigate whether subtle structural abnormalities of the eye contribute to the visual deficit in amblyopia
- To understand the impact of amblyopia on everyday visual function and quality of life measures.
Dyslexia & Reading
Dyslexia is a neurological disorder in which there are specific difficulties with word recognition, reading and often short-term memory. Associated anomalies of binocular motor co-ordination contribute to visual problems.
Our work with dyslexics is aimed at:
- Improving methods for assessment and treatment of binocular motor anomalies.
- Improving our understanding of the characteristics and causes of binocular problems in dyslexia.
- Investigating the associations between binocular motor anomalies and deficits in visual short-term memory and attention.
How good does your vision need to be to perform a specific task?
This is a fundamental question for many day to day tasks, particularly those where an error has implications for public safety, such as driving a motor vehicle. Many occupations set a minimum requirement for a particular level of vision at the point of entry. The Disability Discrimination Act has highlighted the importance of providing an evidence base for visual standards, in other words, there needs to be proof that those with vision that meets the standard or better, are capable of reaching an acceptable level of performance when undertaking the task, and those whose vision is poorer than a particular standard will demonstrate inadequate performance that may impact upon safety.
The work we undertake involves a detailed analysis of the visual tasks involved in particular occupations and activities, to define those that represent the greatest visual demand and those that have the greatest safety implications. An experimental protocol can then be designed to test the performance of individuals with respect to these critical visual tasks, and compare the findings with standard clinical and psychophysical tests of vision, spanning visual acuity, contrast sensitivity, colour discrimination, visual field sensitivity and extent and glare, and others.
Using these methods we, along with collaborators such as the Institute of Occupational Medicine, have advised or developed evidence based visual standards for bodies such as the Rail Standards Safety Board, Department for Transport, Public Carriage Office and Civil Aviation Authority.
Is there anything elite about the vision of elite sportspeople?
It seems obvious that good vision is a pre-requisite for the exceptional visuomotor skills needed in many sports. For example, to catch a cricket ball requires anticipation of the speed and direction of travel of the ball. But do elite cricketers have superior vision than sub-elites? Does having 'excellent' vision go hand-in-hand with elite sporting ability? And if elites do have superior vision than non-elites, is this the cause or a consequence of their exceptional ability? These are the questions that are of interest to us in our current research, funded by the BBSRC. This project represents a collaboration between St. Andrews University and Liverpool John Moores University, with the University of Bradford (Schools of Optometry & Vision Science and Engineering) as the lead institution.
From a review of 'popular' sports literature, it appears that two beliefs are commonly held, first, that athletes have superior use of their vision than non-athletes and second that vision therapy improves sporting performance. However, neither of these holds up under scientific scrutiny. Previous research has downplays the influence of visual factors, but we suggest this is because the right tests may not have been included: tests that measure visual brain function, not simply eye function. Our research is establishing whether elite sporting performance is linked to visual abilities determined by brain functioning in vision-specific brain areas, and, if the two are linked, to examine how they are linked. Previous research in another elite population (pilots) shows that some laboratory measures of vision are linked to flying performance whereas clinical visual measures do not.
We are assessing vision and visuo-motor skills in elite- and club-level cricketers and in novices. We selected cricket because of the complexity of its visual demands. However, our results will generalise to other sports, particularly those with a fast-moving ball (e.g. tennis). We have established links with the England & Wales Cricket Board and with a centre of cricketing excellence, and both are providing us with access to elite players for testing.
We are developing and running behavioural tests designed specifically to measure visual brain function. Studies of brain imaging tell us about brain functioning and connections between processing networks, but it is only feasible to study a small number of elite athletes using this approach. Our proposed behavioural studies thus offer a more practical approach to studying visual and fine-motor control abilities in elite athletes.
We are measuring visual abilities in situations that mimic the sporting environment; for example, we test the ability to see and discriminate motion and depth, and test the ability to anticipate the future location of a moving object. We are relating these vision measures to performance on a cricket task (one-handed catching) and to a more general hand-eye co-ordination task (pointing). We have infra-red motion-capture camera systems that allow limb and body movements to be carefully measured and monitored when a real-world task (e.g. catching a ball ejected from a ball-machine) is undertaken. Thus, in addition to measuring visuo-motor task success (e.g. proportion of balls caught) we are establishing the movement control parameters for individual sportspeople as they perform these tasks.
To ensure that we fully reveal the extent of the links between visual ability and the fine-motor control required in sport our research examines individual differences in vision between good and poor ball catchers under optimal visual conditions and when vision is degraded (e.g. low light levels) because it is here where the impact of vision-related differences may emerge or be exaggerated.
Although the focus here is to understand the link between visual and motor abilities in high-performance sport our results will hold direct relevance to everyday scenarios where visual perceptual skills limit motor control as we interact with the environment around us. Thus our research aims to identify the nature of the relationship between visual and motor capabilities using elite sport as a vehicle for understanding how perception and action are linked in more everyday tasks.
Visual optics and myopia
Ocular biometry and refractive error.
Myopia is becoming increasingly common, particularly in the Far-East. Inherited factors do not fully explain the increase in myopia prevalence that has been evident over the last few decades. Ocular biometric studies, using the IOLMaster for example, show that elongation of the axial length of the eye is the principal structural correlate of myopia. Our research in corneal topography has been used to correct myopia using custom-made rigid contact lenses.
There is increasing evidence for the role of environmental factors, e.g. nearwork, in the onset and progression of myopia. Our research group is particularly interested in the role of the following factors in myopia progression:
- Peripheral ocular dimensions
- Diurnal variation in eye size
- Exposure to defocus
- Task illumination
- Visual display unit use
Vision and quality of life
The diagnosis and management of visual anomalies, have psychosocial effects on patients which are of interest to our research group.
- Measuring quality-of-life changes due to amblyopia, strabismus, cataract and cataract surgery.
- Investigation of the effect of referral on patient anxiety.