Binocular Visual Field Defects Research Articles

Exploring Eye Movements in Patients with Glaucoma When Viewing a Driving Scene

BackgroundGlaucoma is a progressive eye disease and a leading cause of visual disability. Automated assessment of the visual field determines the different stages in the disease process: it would be desirable to link these measurements taken in the clinic with patient's actual function, or establish if patients compensate for their restricted field of view when performing everyday tasks. Hence, this study investigated eye movements in glaucomatous patients when viewing driving scenes in a hazard perception test (HPT).Methodology/Principal FindingsThe HPT is a component of the UK driving licence test consisting of a series of short film clips of various traffic scenes viewed from the driver's perspective each containing hazardous situations that require the camera car to change direction or slow down. Data from nine glaucomatous patients with binocular visual field defects and ten age-matched control subjects were considered (all experienced drivers). Each subject viewed 26 different films with eye movements simultaneously monitored by an eye tracker. Computer software was purpose written to pre-process the data, co-register it to the film clips and to quantify eye movements and point-of-regard (using a dynamic bivariate contour ellipse analysis). On average, and across all HPT films, patients exhibited different eye movement characteristics to controls making, for example, significantly more saccades (P<0.001; 95% confidence interval for mean increase: 9.2 to 22.4%). Whilst the average region of ‘point-of-regard’ of the patients did not differ significantly from the controls, there were revealing cases where patients failed to see a hazard in relation to their binocular visual field defect.Conclusions/SignificanceCharacteristics of eye movement patterns in patients with bilateral glaucoma can differ significantly from age-matched controls when viewing a traffic scene. Further studies of eye movements made by glaucomatous patients could provide useful information about the definition of the visual field component required for fitness to drive.

What do patients with glaucoma do when they search and look at everyday scenes?

Abstract Purpose To test the hypothesis that patients with bilateral glaucoma exhibit different eye movements compared to normally‐sighted subjects when viewing computer displayed photographs, or searching for features or items within them. Methods Thirteen glaucoma patients and 17 age‐matched subjects with normal vision viewed 28 randomised digital photographs of various everyday scenes displayed on a computer screen for 3 seconds each. Subjects were instructed to view the images as they would when looking at a slideshow. The subjects then viewed another set of images, but were timed to find a feature or item in the scene. Eye movements were simultaneously recorded using an Eyetracking system. Results In the passive viewing experiment, there was a significant reduction in the average number of saccades for glaucoma patients compared to controls (p&lt;0.0001). In addition, average fixation duration was longer and the average area scanned was more restricted in patients compared to controls. In the search task glaucoma patients took, on average, longer to find the objects (p&lt;0.0001) compared to controls. For this task, saccades were still reduced in number. In some cases, individual scanning patterns appeared related to the type and nature of the binocular visual field defect. Conclusion Eye movement behaviour in patients with glaucomatous defects in both eyes differ from normal‐sighted subjects when viewing images and photographs. These patients with glaucoma find it more difficult to locate items within scenes compared to normally sighted subjects. Acknowledgements: This work is generously supported by an unrestricted grant from the Special Trustees of Moorfields Eye Hospital.

Effect of Restriction of Vision on Driving Performance

Experts estimate that vision provides 90 percent of the sensory input used by drivers to guide and control their vehicles. In a field study, investigators restricted vision to determine the effect on driving performance. Commonly occurring binocular visual-field defects were simulated for a group of young normal subjects and then their driving performance was assessed on a private closed rural road, free of other vehicles. The monocular condition did not significantly affect performance for any of the driving tasks assessed; however, restricting binocular vision had several effects. When binocular vision was 40 percent or less, the time to complete the course significantly increased, the ability to detect and correctly identify road signs decreased, and the ability to avoid obstacles and maneuver through limited space decreased. Accuracy of road positioning and reversing were also impaired. Some other driving tasks, such as driver's ability to estimate speed and stopping distance, were not affected by restriction of binocular visual fields. More definitive research on the interrelationship between visual performance and performance on the road is necessary.

Effect of restriction of the binocular visual field on driving performance

The importance of the visual field on driving performance was investigated. This was undertaken by simulating binocular visual field defects for a group of young normal subjects and assessing the impact of these defects on performance on a driving course. Constriction of the binocular visual field to 40° or less, significantly increased time taken to complete the course, reduced the ability to detect and correctly identify road signs, avoid obstacles and lo manoeuvre through limited spaces. Accuracy of road positioning and reversing were also impaired. Constriction of the binocular visual field did not significantly affect speed estimation, stopping distance, or the time taken for the reversing and manoeuvring tasks. The monocular condition did not significantly affect performance for any of the driving tasks assessed.

Effect of restriction of the binocular visual field on driving performance

The importance of the visual field on driving performance was investigated. This was undertaken by simulating binocular visual field defects for a group of young normal subjects and assessing the impact of these defects on performance on a driving course. Constriction of the binocular visual field to 40 or less, significantly increased time taken to complete the course, reduced the ability to detect and correctly identify road signs, avoid obstacles and to manoeuvre through limited spaces. Accuracy of road positioning and reversing were also impaired. Constriction of the binocular visual field did not significantly affect speed estimation, stopping distance, or the time taken for the reversing and manoeuvring tasks. The monocular condition did not significantly affect performance for any of the driving tasks assessed.