Continuous measurements of eyeball area and their spectrum analyses. Toward the quantification of rest rhythm of horses by image processing

The motion of eyelids and eyeballs in domestic animals has been recognized as agreeing well with the sleep depth estimated by spectrum analyses of an electroencephalogram for half-closed eye and fully closed eye. This study aimed at quantitative estimation of the rest rhythm of horses by analysis of eyeball movement. The mask attached with a miniature CCD camera was newly developed. The continuous images of the horse eye for about 24 hours were transmitted by a telemetry system and were recorded to a time-lapse video recorder. The continuous images were captured on hard disc (rate 1 frame / 2 sec), the time information was obtained by OCR technology, the eyeball area was smoothed to average gray values, and threshold obtained for segmentation. The eyeball area was obtained via image processing and the spectrum analyzed. The temporal trend, the histogram and the spectrum of the eyeball area were calculated. As for the results, the fluctuating status of the eyeball area was analyzed quantitatively, and the rest rhythm of horses was clearly observed. It is possible to apply this technology to other animals.