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Title: Duration related effects in reading performance in individuals with visual impairment
Author: Muk, Chee Yong Kingsley
ISNI:       0000 0004 8504 9689
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2020
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Recent evidence suggests that a decline in reading speed with time due to fatigue can be observed in an extended reading test, although only in individuals with a mild visual impairment. This effect could be relevant to the leisure reading ability in individuals with visual impairment. To date, there is no study investigating duration related effects in participants using low vision aids (LVA) for a reading task. This study aims to investigate if any negative duration related effects on the reading speed can be identified within a 15-minute reading test and whether the measurement parameters can predict the success of a LVA. The investigation was conducted in 26 young and 31 elderly normally-sighted adults, and 61 visually impaired participants. The normally-sighted participants were tasked to perform an approximately 15-minute silent reading task with habitual vision, with simulated loss of acuity and contrast sensitivity, and with the use of a hand-held magnifier. Reading slope was computed as the linear slope of the reading speed against time; NRR1 is the median ratio of the successive minutes reading speed relative to the reading speed at the second minute; and NRR2 is the ratio comparing the reading speed at the endpoint to the beginning of the reading test. A negative reading slope or NRRs of < 1.0 would indicate a decline in reading speed with time. Another measurement of fatigue using spontaneous blinking rate (SBR) was also explored. The SBR slopes was computed based on the linear slope of SBR against time. Most of the young adults and elderly participants showed an increase or almost constant reading speed with time in a silent reading test based on the reading slopes (Young: 0.37, IQR:2.10 wpm/min; Elderly: 0.43, IQR:2.24 wpm/min), median NRR1 (Young: 1.14, IQR:0.25; Elderly: 1.01, IQR: 0.43), and median NRR2 (Young: 1.13, IQR:0.36; Elderly: 1.02, IQR: 0.52) in the condition with the use of a hand-held magnifier. In the same condition, the SBR remains relatively constant with time (Young: 0.00, IQR:0.49 SBR/min; Elderly: -0.01, IQR: 0.31 SBR/min) and the SBR slopes were poorly associated with reading slopes for all the participants (r=0.24, p=0.08). Likewise, the visually impaired participants showed an overall mean reading slope of 1.40 (SD ± 1.87) swpm/ row of words and a mean NRR2 of 1.13 (SD ± 0.37) suggesting an increase in reading speed with time using their optical magnifiers. Forty-eight (79%) visually impaired participants showed a positive reading slope, with almost half of them (n = 30) showing repeated positive reading slopes in the second visit. The duration related effects indicators were not associated with duration of leisure reading in everyday life (reading slope: r = 0.06, p= 0.62, NRR2: r = -0.09, p= 0.49) or frequency of LVA usage (reading slope: r = 0.06, p= 0.62, NRR2: r = -0.01, p= 0.96) in the visually impaired participants. In conclusion, negative duration related effects cannot be captured within a 15-minute reading test. The duration related effects indicators (i.e. reading slopes and NRR) were not able to predict the success of magnifier usage in a clinical setting.
Supervisor: Dickinson, Christine Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available