Eye movements and reading in glaucoma: observations on patients with advanced visual field loss
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To investigate the relationship between reading speed and eye movements in patients with advanced glaucomatous visual field (VF) defects and age-similar visually healthy people.
Eighteen patients with advanced bilateral VF defects (mean age: 71, standard deviation [SD]: 7 years) and 39 controls (mean age: 67, SD: 8 years) had reading speed measured using short passages of text on a computer set-up incorporating eye tracking. Scanpaths were plotted and analysed from these experiments to derive measures of ‘perceptual span’ (total number of letters read per number of saccades) and ‘text saturation’ (the distance between the first and last fixation on lines of text). Another eye movement measure, termed ‘saccadic frequency’ (total number of saccades made to read a single word), was derived from a separate lexical decision task, where words were presented in isolation.
Significant linear association was demonstrated between perceptual span and reading speed in patients (R 2 = 0.42) and controls (R 2 = 0.56). Linear association between saccadic frequency during the LDT and reading speed was also found in patients (R 2 = 0.42), but not in controls (R 2 = 0.02). Patients also exhibited greater average text saturation than controls (P = 0.004).
Some, but not all, patients with advanced VF defects read slower than controls using short text passages. Differences in eye movement behaviour may partly account for this variability in patients. These patients were shown to saturate lines of text more during reading, which may explain previously-reported difficulties with sustained reading.
KeywordsGlaucoma Reading Eye movements Visual fields Perimetry
The authors thank the following: Ryo Asaoka for help with patient recruitment and ophthalmic examinations, Fiona Glen for testing participants and data collection, David Garway-Heath for comments on aspects of the experimental design, and Iván Marín-Franch for plotting scanpaths and some discussion about the manuscript.
This study was conducted as part of a programme of work funded by the Investigator-Initiated Studies Programme of Merck Sharp & Dohme Ltd.
Conflict of interest
DPC has previously received unrestricted research funding from Allergan, Pfizer, Merck, and honoraria for lecturing from Allergan and Merck.
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