Progressing myopes have reduced accommodative response to negative defocus (1). One possible explanation for the accommodative anomalies associated with myopia is that the optical quality of the retinal image is reduced, making it more difficult for myopes to detect and respond appropriately to blur. Myopes also are reported to have a significantly higher blur threshold than emmetropes (2). Recently, prolonged exposure to blurred images has been shown to produce perceptual adaptation (3). An experiment in our laboratory building on the latter result tested whether the change in perceived blur was accompanied by a change in accommodation, and whether the response was different for emmetropes and myopes. Results showed that the accommodative response of myopes was significantly enhanced after exposure to three minutes of blur, while accommodation in emmetropes was not affected by experiencing blur. These results are consistent with up regulation in the oculomotor system, which responds with a greater increase in the accommodative response to improved contrast information caused by blur adaptation. The refractive group differences in accommodative response may be related to differences in the habitual response to image clarity between myopes and emmetropes under normal viewing conditions.

Support: NEI/NIH grant EY01191

1. Gwiazda J, Thorn F et al. (1993). Myopic children show insufficient accommodative response to blur. Invest Ophthalmol Vis Sci 34: 690-4.

2. Rosenfield M and Abraham-Cohen, J (1999). Blur sensitivity in myopes. Optom Vis Sci 76: 303-7.

3. Webster M, Georgeson M et al. (2002). Neural adjustments to image blur. Nat Neurosci 5: 839-40.