Abstract: Systems and methods for detecting onset, presence, and progression of particular states, including hypoxia, include observing eye movements of a subject to and correlating the observed movements to known baseline or hypoxic conditions. A detection system may record eye movement data from a user, compare the eye movement data to a data model comprising threshold eye movement data samples, and from the comparison make a determination whether or not hypoxia, fatigue, or other detrimental conditions are present. The detection system may alert the user to take corrective action if onset or presence of a dangerous condition is detected. The eye movements detected include saccadic and intersaccadic parameters such as intersaccadic drift velocity. Measurements may be collected in situ while the subject is performing normal duties, processed to determine indicators of detrimental conditions, and reported to the subject within a few seconds.