The time course of blur adaptation in emmetropes and myopes
Article first published online: 12 MAY 2013
Ophthalmic & Physiological Optics © 2013 The College of Optometrists
Ophthalmic and Physiological Optics
Special Issue: Understanding & Controlling Myopia - Where We Are Now. A compilation to honour the research achievements and mark the passing of Josh Wallman
Volume 33, Issue 3, pages 305–310, May 2013
How to Cite
The time course of blur adaptation in emmetropes and myopes. Ophthalmic Physiol Opt 2013, 33: 305–310. doi: 10.1111/opo.12031, , , , .
- Issue published online: 12 MAY 2013
- Article first published online: 12 MAY 2013
- Manuscript Accepted: 10 JAN 2013
- Manuscript Received: 2 NOV 2012
- Bradford School of Optometry
- Vision Science departmental studentship
- Engineering and Physical Sciences Research Council
- blur adaptation;
- optical defocus;
- visual acuity
This study examined the effect of myopic defocus on visual acuity (VA) over time, with attention being paid to the first point at which blur adaptation had a significant and measurable effect on defocused VA. Visual acuity was sampled at a higher rate than previous studies in order to assess the time course of blur adaptation processes in myopic and emmetropic observers.
Participants were 24 normally-sighted observers (12 emmetropes and 12 myopes, median age: 22.5 years). All ametropic participants wore their full refractive correction throughout the experiment. 1 D and 3 D of myopic defocus were introduced in two separate, randomised sessions. Visual acuity was measured using Test Chart 2000 at 2 min intervals over a 30 min session whilst looking through defocus lenses. Recovery clear VA was also measured every 2 min for a further 20 min.
Defocused VA was found to improve significantly within 4 min after the introduction of defocus for both 1 D (P < 0.0001) and 3 D conditions (P < 0.0001). The improvements reached a plateau shortly after, with no significant further improvements in defocused VA after 6 min. There were no significant differences found in the temporal blur adaptation profiles between emmetropes and myopes (P = 0.267). Data were fitted with an exponential decay function; the lowest R2 value for this fit was 0.95.
Blur adaptation has a clinically significant and measurable effect on VA within 4 min of exposure to defocus. This finding indicates that the visual system instigates the neural compensatory mechanisms shortly after the appearance of defocus. Our results relate particularly to real-life vision of uncorrected myopes or myopes who remove their correction for part of the day.