School-day biorhythms of threshold exposure duration for recognition of test objects in schoolchildren of grades 7 to 11
M.B. Zheliznik, Graduate Student
V.I. Serdiuchenko, Dr Sc (Med)
O.I. Dragomiretska, researcher
Filatov Institute of Eye Diseases and Tissue Therapy, NAMS of Ukraine
Odessa, Ukraine
E-mail: virais@ukr.net
Background: To the best of our knowledge, no study has yet reported on biorhythms of Threshold Exposure Duration for Recognition of Test Objects (TEDRTO).
Purpose: To investigate biorhythms of TEDRTO over a school day in children learning under intensive visual load conditions.
Materials and Methods: Ninety eight ophthalmologically healthy children (aged 13 to 17 years) attending a boarding school with advanced learning of a number of subjects underwent examination. A special electronic apparatus was used to present a test object (a Landolt’s ring having an angular size of 8 minutes of arc) to the child. Binocular TEDRTO measurements were performed at five time points during the day: at 8 o’clock AM, 11 o’clock AM, 2 o’clock PM, 4 o’clock PM, and 8 o’clock PM).
Results: Friedman's non-parametric test demonstrated that TEDRTO values gradually and statistically significantly increased (χ² = 52.4; р=0.00000) during a school day. In addition, the number of children with TEDRTO values greater than 1 ms at various times of measurement gradually increased during a school day, and these children usually complained of increased visual fatigue.
Conclusions: There was a statistically significant worsening in TEDRTO values in schoolchildren learning over a day under intensive visual load conditions.
Key words: threshold exposure duration for recognition of test objects, schoolchildren, circadian biorhythms   
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