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E. Mallen, M. P. Cufflin, A. M. Mankowska; Blur Adaptation in the Parafoveal Region of the Visual Field. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1115.
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© ARVO (1962-2015); The Authors (2016-present)
Blur adaptation is the increase in visual resolution that occurs over time following initial degradation of the retinal image, for example, when a myopic individual removes their corrective lenses and stays uncorrected for a period of time. These adaptive processes are well documented at fixation, but data on the potential for a blur adaptation effect at parafoveal locations is sparse.
Ten young adult subjects (3 emmetropes and 10 myopes) were recruited. A 2 alternative forced choice psychophysical task, utilising a 3/1 staircase, was used to determine spatial resolution by presenting Gabor patches at fixation, and at 2, 4 and 6 degrees into the nasal visual field. Spatial resolution was determined with the best refractive correction in place, under +1D of refractive blur, and under +1D of refractive blur following a 30 minute period of blur adaptation (watching a broadcast television picture with +1D of defocus in place).
In agreement with previous work, a substantial decline (mean: 20.0 to 12.8 cycles per degree) in spatial resolution was observed at fixation following the introduction of +1D blur. An increase in spatial resolution, over and above the initial blur condition (mean: 12.8 to 13.5 cycles per degree), was seen at fixation following 30 minutes of blur adaptation. Under optimum refractive conditions, mean reductions in spatial resolution at 2, 4 and 6 degrees were 5.0, 7.5 and 9.3 cycles per degree respectively. At parafoveal locations, a trend was seen for an increase in spatial resolution following blur adaptation; mean spatial resolution at 2 degrees: 9.6 (pre-adaptation) to 11.1 (post-adaptation) cycles per degree. Smaller improvements in spatial resolution were seen at 4 and 6 degrees following blur adaptation.
This experiment suggests that parafoveal regions of the visual field may be amenable to blur adaptive effects. These effects appear to diminish as retinal eccentricity increases. Further work is now necessary to determine whether off-axis blur adaptation varies as a function of central refractive error.
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