Myopic progression and dark focus variation in optometric students during the first academic year.
BACKGROUND: The aim of this research was to investigate the change in refractive error (RE) of optometric students during their first academic year and whether these changes relate to changes in their dark focus (DF). METHOD: The RE and DF of 64 students were measured objectively every three months during the first academic year, a total of four times, using a Canon R-1 infrared optometer. Thirty-five of the 64 students had an additional RE and DF measurement three weeks immediately after their Summer vacation. Students completed a survey regarding the near work demands they experienced during the Winter break and the teaching semesters. RESULTS: Over nine months, the average RE of the students changed significantly from -2.22 +/- 1.93 (SD) D to -2.50 +/- 2.05 D (p = 0.0002). The rate of myopic progression averaged -0.37 dioptres per year. Inclusion of measurements taken on 35 students immediately after the Summer vacation showed that their change in RE during the Summer vacation was not significant (p = 0.79). For these subjects, the DF measured immediately after the vacation was significantly lower than the DF measured before the vacation (p = 0.007). The reduction in the DF after the vacations corresponded to a period of relative myopic stability in these subjects. CONCLUSIONS: The results of this study suggest that optometric students performing extensive near work are at risk of developing myopia. The variation of their DF values indicates the changing demand for near work during different periods of the year. After Winter and Summer vacations, the DF was lower and the myopic progression was suspended. These findings further support the notion that myopic progression is related to high near work demands and suggest that this progression can be slowed by a period of reduced near work, for example, vacation periods.