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Contrast sensitivity changes due to glaucoma and normal aging: low-spatial-frequency losses in both magnocellular and
Allison M McKendrick1, Geoff P Sampson, Mark J Walland
1Department of Optometry and Vision Sciences, University of Melbourne, Carlton VIC 3053, Parkville, Australia. allisonm@unimelb.edu.au
Investigative Ophthalmology & Visual Science
|April 27, 2007
Summary
Normal aging and glaucoma both reduce contrast sensitivity in the magnocellular (M) and parvocellular (P) visual pathways. Glaucoma causes a further, non-selective decline in sensitivity, impacting low-spatial-frequency channels in both pathways.
Area of Science:
- Ophthalmology
- Neuroscience
- Visual Science
Background:
- Contrast sensitivity, crucial for visual perception, declines with age.
- The magnocellular (M) and parvocellular (P) pathways process visual information differently and may be differentially affected by aging and disease.
- Glaucoma is a progressive optic neuropathy often associated with visual field loss.
Purpose of the Study:
- To investigate how normal aging and glaucoma impact low-spatial-frequency contrast sensitivity.
- To differentiate the effects on the magnocellular (M) and parvocellular (P) visual pathways using specialized tests.
Main Methods:
- Contrast sensitivity was measured using steady- (presumed M) and pulsed- (presumed P) pedestal paradigms across low spatial frequencies (0.25-2 cyc/deg).
- Participants included younger controls, older controls, and patients with glaucoma tested at foveal and midperipheral locations.
- Glaucoma patients were assessed in areas of both early visual field loss and normal visual field.
Main Results:
- Older adults showed reduced contrast sensitivity compared to younger adults in both M and P pathway tests, across all tested locations.
- Glaucoma patients exhibited further sensitivity reductions compared to older controls, particularly in areas of early visual field loss.
- Sensitivity was also diminished in midperipheral "normal" visual field areas for the pulsed (P) pathway in glaucoma patients.
Conclusions:
- Aging impairs contrast sensitivity in both M and P pathways at low spatial frequencies.
- Glaucoma exacerbates this sensitivity loss, affecting both M and P pathways non-selectively.
- Early glaucoma appears to equally impair the low-spatial-frequency-sensitive channels of both visual pathways.
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