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Prolonged near tasks may cause axial elongation
Br J Ophthalmol. 2011;95(5):652-656.
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Young adult emmetropes and myopes show an increase in axial length following periods of sustained near work, according to a study.
"We found that certain subgroups of myopes seem to be more susceptible to this transient elongation, and both [early-onset myopes] and [progressing myopes] showed increases in axial length following a prolonged near task that were significantly greater than emmetropes," the authors said.
The study included 20 myopes and 20 emmetropes, ages 18 to 33 years. Myopes were classified as either early onset or late onset and either stable or progressing.
Immediately after subjects completed the near task, researchers observed significant changes in axial length.
Average elongation was 0.027 ± 0.021 mm in early onset subjects, 0.014 ± 0.020 mm in late onset subjects, 0.031 ± 0.022 mm in progressing subjects and 0.014 ÷ 0.018 mm in stable subjects. Emmetropes had an average elongation of 0.010 ± 0.015 mm.
After a 10-minute regression period, axial length was not significantly different from baseline.
Further study is necessary to determine the time course of axial length change, as well as the relationship between axial length and refractive changes after near work, the authors said.