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Effects of glaucoma on detection and discrimination of image blur
Bham, Habiba A. Denniss, Jonathan
Bham, Habiba A.
Denniss, Jonathan
Publication Date
2022-05
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© 2022 The Authors. This is an Open Access article distributed under the Creative Commons CC-BY license (http://creativecommons.org/licenses/by/4.0/)
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Yes
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openAccess
Accepted for publication
19/10/2021
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Abstract
Blur is one of the most commonly reported visual symptoms of glaucoma, but it is not
directly measured by current clinical tests. We aimed to investigate the effects of
glaucoma on detection and discrimination of image blur.
People with glaucoma, separated into two groups with (n=15) or without (n=17)
central visual field defects measured by 10-2 perimetry, and an age-similar control
group (n=18) participated. First, we measured contrast detection thresholds centrally
using a 2-interval forced choice procedure. We then measured blur detection and
discrimination thresholds for the same stimuli (reference blurs 0, 1 arcmin
respectively) using a 2-alternative forced choice procedure under two contrast
conditions; 4x individual detection threshold for the low contrast condition, 95%
contrast for the high contrast condition. The stimulus was a horizontal edge bisecting
a hard-edged circle of 4.5° diameter. Data were analysed by linear mixed modelling.
Contrast detection thresholds for the glaucoma group with central visual field defects
were raised by 0.014 ± 0.004 (mean ± SE, Michelson units) (p=0.002) and by 0.011
± 0.004 (p=0.03) relative to control and glaucoma without central visual field defect
groups respectively. Blur detection and discrimination thresholds were similar
between groups, with small elevations in blur detection thresholds in the glaucoma
groups not reaching statistical significance (detection p=0.29, discrimination p=0.91).
The lower contrast level increased thresholds from the higher contrast level by 1.30
± 0.10 arcmin (p<0.001) and 1.05 ± 0.096 arcmin (p<0.001) for blur detection and
discrimination thresholds respectively.
Early-moderate glaucoma resulted in only minimal elevations of blur detection
thresholds that did not reach statistical significance in this study. Despite the
prevalence of blur as a visual symptom of glaucoma, psychophysical measurements
of blur detection or discrimination may not be good candidates for development as
clinical tests for glaucoma
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Citation
Bham HA and Denniss J (2022) Effects of glaucoma on detection and discrimination of image blur. Ophthalmic and Physiological Optics. 42(3): 471-481.
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