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The relationship between object spatial profile and accommodation microfluctuations in emmetropes and myopes
Mhairi Day1, Lyle S Gray, Dirk Seidel
1Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, UK. m.day@gcal.ac.uk
Journal of Vision
|October 9, 2009
Summary
Accommodation microfluctuations, crucial for vision control, differ between myopes and emmetropes. Myopes exhibit larger fluctuations, especially at high spatial frequencies, suggesting altered contrast gradient processing in myopia.
Area of Science:
- Ophthalmology
- Visual Neuroscience
- Optometry
Background:
- Accommodation microfluctuations are believed to provide error signals for visual control.
- The contrast gradient of retinal images is a key factor influencing these fluctuations.
- Spatial frequency (SF) of visual targets can modulate the contrast gradient.
Purpose of the Study:
- To investigate the role of spatial frequency in accommodation microfluctuations.
- To compare microfluctuation responses between myopes (MYOs) and emmetropes (EMMs).
- To explore potential differences in contrast gradient processing between these groups.
Main Methods:
- Accommodation responses were measured using autorefraction in 12 MYOs and 12 EMMs.
- Participants viewed sine and square wave targets of varying SFs (0.5-16 cpd) in a Badal system.
- Continuous recording of accommodation responses during target viewing.
Main Results:
- Square wave SF did not alter microfluctuation magnitude.
- Sine wave viewing showed minimal microfluctuations at mid-SFs (2-4 cpd), increasing at low and high SFs.
- MYOs displayed significantly larger microfluctuation increases at high SF (16 cpd) compared to EMMs.
- MYOs consistently exhibited larger microfluctuations than EMMs.
Conclusions:
- Accommodation microfluctuations likely monitor the cortical image contrast gradient for error detection.
- MYOPIC individuals may process a shallower contrast gradient.
- These findings suggest potential differences in visual feedback mechanisms in myopia.
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