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Amanda A. Alvarez, Christine F. Wildsoet; Quantifying the Light Environments of Myopes and Emmetropes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2503.
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Interest in the role of light in eye growth modulation has been stimulated by recent results showing slowed rates of myopia genesis in chickens and monkeys reared in bright light (e.g. Ashby, Smith). This study investigated light exposure patterns in young adult university students in relation to their refractive error.
Young adult subjects (19-23 years old) wore light sensors that recorded ambient light intensity every other second, for 8 hours a day. Data collection took place over three months, with each subject participating on seven randomly selected days. Non-cycloplegic autorefraction and axial length measurements were taken prior to data collection. Subjects were instructed to not modify their behavior, so the data reflected daily light exposure in their usual visual environments.
Light exposure for emmetropes and myopes did not differ in terms of either maximum intensity or cumulative light received. Brief periods of high intensity exposure accounted for the majority of the total light exposure (80% or more) of our subjects, with most of them spending less than 15 minutes a day in levels comparable to direct sunlight. There were no significant correlations between axial length or refractive error, and time in high intensity light. The frequency of change in light intensity was also not correlated with axial length or refractive error.
Although this cross-sectional investigation of light exposure did not yield obvious differences along the dimension of refractive error, objective documentation of the visual environmental and behavioral differences of humans is critical to elucidating the etiology of the worldwide myopia epidemic.
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