Yes / PURPOSE. Glaucoma raises contrast detection thresholds, but our natural visual environment
is dominated by high contrast that may remain suprathreshold in early to moderate
glaucoma. This study investigates the effect of glaucoma on the apparent contrast of
visible stimuli.
METHODS. Twenty participants with glaucoma with partial visual field defects (mean age,
72 ± 7 years) and 20 age-similar healthy controls (mean age, 70 ± 7 years) took part.
Contrast detection thresholds for Gabor stimuli (SD, 0.75°) of four spatial frequencies
(0.5, 1.0, 2.0, and 4.0 c/deg) were first measured at 10° eccentricity, both within and
outside of visual field defects for participants with glaucoma. Subsequently, the contrast
of a central Gabor was matched to that of a peripheral Gabor with contrast fixed at
two times or four times the detection threshold. Data were analyzed by linear mixed
modelling.
RESULTS. Compared with controls, detection thresholds for participants with glaucoma
were raised by 0.05 ± 0.025 (Michelson units, ± SE; P = 0.12) and by 0.141 ± 0.026
(P < 0.001) outside and within visual field defects, respectively. For reference stimuli at
two times the detection contrast, matched contrast ratios (matched/reference contrast)
were 0.16 ± 0.039 (P < 0.001) higher outside compared with within visual field defects
in participants with glaucoma. Matched contrast ratios within visual field defects were
similar to controls (mean 0.033 ± 0.066 lower; P = 0.87). For reference stimuli at four
times the detection contrast, matched contrast ratios were similar across all three groups
(P = 0.58). Spatial frequency had a minimal effect on matched contrast ratios.
CONCLUSIONS. Despite decreased contrast sensitivity, people with glaucoma perceive the
contrast of visible suprathreshold stimuli similarly to healthy controls. These results
suggest possible compensation for sensitivity loss in the visual system. / Supported by a College of Optometrists PhD Scholarship. / Research Development Fund Publication Prize Award winner, June 2020
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/17921 |
| Date | 17 July 2020 |
| Creators | Bham, H.A., Dewsbery, S.D., Denniss, Jonathan |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Article, Published version |
| Rights | Copyright 2020 The Authors. This work is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). |
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