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N. D. Smith, F. G. Rauscher, C. M. Chisholm, D. F. Edgar, J. L. Barbur, D. F. Garway-Heath, D. P. Crabb; Eye Movements in Patients With Glaucoma When Viewing a Driving Hazards Perception Test. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4450.
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To examine eye movements in glaucomatous patients when viewing a computer based driving hazards perception test (HPT) and make comparisons with normal control subjects.
The HPT has been a component of the UK driving licence test since November 2002: it consists of a series of short film clips of a moving road scene viewed from a driver’s perspective. Each film clip includes hazards, such as a pedestrian unexpectedly crossing, that required the camera car to change direction or slow down. Nineteen patients with bilateral glaucoma and 25 age-matched normal control subjects were considered for this study. Each subject was instructed to find the hazards in the clips, but this detection data was not the subject of this study. Rather, eye movements were monitored during the HPT with the SMI iView X High-Speed System (1.03.03) sampling at 240Hz, yielding point-of-regard data every 4ms. Computer software was purpose written to process the data, co-register it to the film clips and to analyse the number of saccades, eye-gaze patterns, direction and length of scan paths in a novel fashion.
Around 8 million point-of-regard (x,y) values from 15 HPT clips were quantified by the software for this study. There was considerable evidence of a difference between glaucomatous patients and controls in the average number of saccades (P<0.001) across the clips. Patients with overlapping defects as quantified by the binocular integrated visual field1 also yielded average eye-gaze patterns that fell significantly outside the reference interval yielded from the normal control data. There was also some evidence of an effect of directional eye movements in the patients as compared to controls.
This study provides some evidence that eye movement patterns in patients with glaucoma differ from controls when viewing a moving road and traffic scene; these differences are particularly evident in patients with overlapping bilateral defects as determined by the integrated visual field. 1. Crabb DP et al (2004). A practical approach to measuring the visual field component of fitness to drive. Br J Ophthalmol 88: 1191-1196.
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