Proceedings of the Royal Society of London. Series B: Biological Sciences
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Improving vision: neural compensation for optical defocus

Mark Mon-Williams

Mark Mon-Williams

Perception and Motor Control Laboratory, Department of Human Movement Studies, Connell Building, University of Queensland, St Lucia, Queensland 4072, Australia

Department of Psychology, University of Reading, 3 Earley Gate, Reading RG6 6AL, England

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,
James R Tresilian

James R Tresilian

Perception and Motor Control Laboratory, Department of Human Movement Studies, Connell Building, University of Queensland, St Lucia, Queensland 4072, Australia

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,
Niall C Strang

Niall C Strang

Centre for Eye Research, Queensland University ofTechnology, Kelvin Grove, Queensland 4059, Australia

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Puja Kochhar

Puja Kochhar

Department of Psychology, University of Reading, 3 Earley Gate, Reading RG6 6AL, England

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and
John P Wann

John P Wann

Department of Psychology, University of Reading, 3 Earley Gate, Reading RG6 6AL, England

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    Anecdotal reports abound of vision improving in myopia after a period of time without refractive correction. We explored whether this effect is due to an increased tolerance of blur, or whether it reflects a genuine improvement in vision. Our results clearly demonstrated a marked improvement in the ability to detect and recognize letters following prolonged exposure to optical defocus. We ensured that ophthalmic change did not occur, and thus the phenomenon must be due to a neural compensation for thedefocus condition. A second set of experiments measured contrast sensitivity and found a decrease in sensitivity to mid–range (5–25) cycles deg−1 spatial frequencies following exposure to optical defocus. The results of the two experiments may be explained by the unmasking of low contrast, high spatial frequency information via a two–stage process: (1) the pattern of relative channel outputs is maintained during optical defocus by the depression of mid–range spatial frequency channels; (2) channel outputs are pooled prior to the production of the final percept. The second set of experiments also provided some evidence of inter–ocular transfer, indicating that the adaptation process is occurring at binocular sites in the cortex.