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B. Jiang, K. Seger, S. Schatz; Refractive Error and Dark Focus Before and After Summer Vacation for 37 Optometry Students . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2734.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate how the refractive error (RE) and dark focus (DF) of 37 optometry students may change after a summer vacation. Methods: The RE and DF were measured objectively by a Canon R-1 infrared optometer on each student's right eye before and immediately after their summer vacation of 2002. A bright Maltese cross presented on a dark computer screen served as a target in the RE measurement. The target was located 5m in front of the subject and had a mean luminance of 18 cd/sq.m. DF was measured in the dark. Each RE or DF value was calculated as the average sphere-equivalent power of five readings. The DF value was corrected by the RE value measured in the same session. The RE results measured objectively were compared with the results measured by the subjective refraction. Two researchers conducted the two measures, respectively, and they were bi-blind with a third researcher being in charge of the data process. Results: The average REs before and after the summer vacation were -2.34 ± 2.08 (S.D) D and -2.33 ± 2.20 D, respectively. The difference is not significant (t = -0.070, p = 0.94). The average DF values showed a significant change (t = -2.91 , p = 0.003) from -0.44 D to -0.25 D after the summer vacation. Comparison of the results in RE between the objective and subjective measurements showed a high correlation (R=0.965, p<0.0001). The slopes of the regression lines were 1.06, demonstrating that the objective measurement tended to provide a slight negative value. Conclusions: The results of RE and DF changes are consistent with previous reports. The average DF value became lower indicating that there was an accommodative relaxation when the students had less near work during the summer. For the RE, we found that the average RE of these students in the past 9 months before the summer vacation changed with a rate of -0.050 D per three months, however, this progression stopped during the summer recess. We wonder if there are "critical" maximum lengths of near-work time and minimum lengths of break time that affect myopia progression associated with near work. We hope to explore these public health issues in the future.
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