Abstract
The critical flicker fusion frequency (CFF) for full-field illumination is an easily accessible measure for evaluating the functional state of the visual system. A decrease of the CFF is a symptom of some disorder and reason for medical care. Owing to the great number of components of the visual system (which includes the retina, neural pathways, and visual centres), however, diagnosis based on this single measure may be rather uncertain. This is possibly the reason why the diagnostic value of the CFF seems to be underestimated and why corresponding devices are not represented among everyday health evaluation procedures.
We suggest a simple and convenient (even though not precise) device for CFF testing, useful for express-diagnosis of (i) general visual fatigue due to visual strain and (ii) abnormalities related to ophthalmopathology, implying the need of medical care. The simplicity and convenience of the device make it appropriate for monitoring, for example, school pupils in classrooms. A toy-like modification of the device enables testing of pre-school children.
The diagnostic value of simple devices can be increased if the functional differences (relevant to the CFF: colour, movement, etc) of distinct parts of the human visual system are taken into account. Their deviations from the norm can be especially useful for selective diagnosis in some cases. This may be considered when developing further devices for simple express-diagnosis of ophthalmic diseases.
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