A quantitative assessment of EOG eye tracking during free viewing in sighted and in congenitally blind.

Electrooculography (EOG) has long been a reliable tool for detecting blinks and eye movements. However, its application in naturalistic and unrestricted settings has been little explored. We compared the accuracy of EOG-based eye tracking to a video-based tracking system during free viewing with unrestricted head and eye movements, in both normal lighting and complete darkness. Our results show that, with high signal-to-noise data, EOG reliably detects blinks and saccades, comparable to video-based tracking in light and in darkness. Applying our algorithms to EOG data recorded from blind participants or in sighted during eyes closed, eye movements are still effectively identified. In both participant groups, detected blinks and saccades retain characteristic movement profiles such as blink rate and saccade main sequence, though other features like blink length, preferred saccade direction, saccade rate, and saccade amplitude differ. Interestingly, these differences closely align between sighted individuals with eyes closed and blind participants, while remaining distinguishable from surrogate data, highlighting their genuine physiological basis. These findings affirm EOG's robustness as a tool for eye movement and blink analysis in both controlled and naturalistic environments. Our work further emphasizes the presence of blinks and saccadic muscular movements both in sighted individuals with eyes closed and in the congenitally blind.