Vertical saccades and the "rider artifact".

Quantitative studies of vertical saccades are sparse, due to a lack of reliable recording techniques. In this study, electro-oculographic (EOG) and photo-electronystagmographic (PENG) techniques showed that up-directed saccades were faster than down-directed ones. In the EOG recording, however, the velocity of the up-directed saccade was correlated to the size of an artifact caused by movement of the upper eye lid. Further investigations are needed to analyse the characteristics of vertical eye movements.