Analysis of computerized optokinetic nystagmus induction and effect of contrast on ocular fatigue

Optokinetic nystagmus (OKN) is useful in evaluating visual function objectively, and the classical black-and-white-striped OKN drum is being replaced by video or computer monitor. However, the examinee may feel fatigue during test because of high contrast of luminous pattern from monitor. This paper suggests a plan to reduce eye fatigue of participant by decreasing contrast of patterns without reducing OKN response. Alternating black and white stripes are shown on flat-panel liquid-crystal display monitor and moved horizontally to evoke OKN of the examinee, and the OKN wasW observed through electrooculography (EOG). Eye fatigue was estimated from the number of eye blinking, along with dry eye questionnaire according to the contrast of the black and white stripes. White stripes are shown as 300cd/m², and gradual decrement in contrast by 75%, 50%, and 25% were given to investigate the effect of the contrast on the eye fatigue and the OKN. Blinking of the eye was recorded as a video clip and was analyzed by image processing to count the number of blinks while measuring OKN. Experimental results show that incidence of nystagmus does not substantially change with the change of contrast in stimulus pattern but the eye fatigue decreased by the reduction of the contrast. In conclusion, the examinee may choose the contrast option for the OKN test to reduce the stress onto their eye, without affecting the test result.