Retinal micromovement, the viual line, and Donder’ Law

PURPOE: To report the relationhip of the retinal micromovement to the viual line and to confirm the validity of Donder’ Law. METHOD: Two video camera upended from a headband were ued to record eye (video-oculography) and head movement. Eye poition in held gaze and following variou trajectorie to a target were recorded in five normal, young ubject. The videotape were analyzed off-line uing a computer algorithm. REULT: Retinal micromovement caue the viual line to trace a zigzag pathway acro the foveola, which ha an approximate diameter of 350 μm (about 2 degree). The mean micromovement wa about 10 μm in 33.3 mec. The cumulative effect of ucceive micromovement may move the viual line acro the foveola from edge to edge depending on the elaped time. When the viual line reache the edge of the foveola it change it direction. When the eye reet to the ame target by different trajectorie, the viual line may alight up to about 350 μm from it original location anywhere within the foveola. CONCLUION: Donder’ Law i upheld becaue for each direction of gaze, and regardle of the trajectory ued to reach that direction of gaze, the retina ha a contant orientation to an index head plane at any given moment in time. Failure to conider that the micromovement caue a hift in the poition of the viual line within the foveola may account for the exception to Donder’ Law found by contemporary reearcher uing invaive recording technique.