Critical Flicker Frequency in Auditory-Deprived Children

Abstract

The visual system of auditory-deprived children deserves special attention since its development and functioning occur without the usual support of the auditory system which stimulates eye movements in response to sound producing objects, helps in their localisation, etc. Moreover, normally, the contributions of the visual and auditory systems to learning at school are comparable but, in the cases of complete or partial deafness, the visual system is the only or the main channel responsible for acquisition and processing of information. In a pilot study, we have found that such specific conditions of visual performance could affect some visual capabilities and indices of functioning, in particular, the critical flicker frequency (CFF). CFF was measured in 63 auditory-deprived children (aged 6 – 9 years) from special kindergartens and schools and in 92 children of the same ages from ordinary schools. The light source was a red-light-emitting diode in a dark plastic cone. Since it is known that CFF depends on the state of fatigue and other conditions, the measurements were performed at several different times of the day in each subject: in the morning before lessons, in the midday after lessons, and during the 2nd or the 3rd lesson before and after a special visual exercise lasting 15 – 20 min. It was found that auditory-deprived children differed from the control group by much larger influence of school work on CFF ( p<0.001): in the control group, the average CFF after lessons was 17% lower than before lessons whereas in the test group, the corresponding lowering was equal to 34%, ie was twice as great. Other differences were less evident or insignificant.