Robust video-oculography for non-invasive autonomic nerve quantification

A relationship between autonomic nerves activity and depression or Alzheimer´s disease has been reported. The quantification of autonomic nerves is expected to serve as a tool for quantifying the of severity of the disease or for early detection. Video-oculography is known as a non-invasive and reliable procedure of measurement of pupil response and is used in clinical practice. However, measuring the transition of pupil areas accurately is often difficult due to eyelid overlap, effects of blinking, eyelashes etc. Current video-oculography only performs thresholding to split pupil area and backgrounds and therefore sometimes has difficult in measuring accurate transitions of pupil reflex. In this study, we developed a robust and accurate method to measure the transition of pupil size. The proposed method introduces an interpolation process using an active contour model and ellipse estimation with selection of reliable contour points and attains robust measurement of pupil area against the abovementioned difficulties. We confirmed our method achieved an extraction accuracy of 98.3 % in precision and 98.9% in recall in average on the tested a total of 8,518 image frames from 30 movies.