A system and/or method for determining human health uses a head-worn apparatus that comprises a head orientation sensor, an eye imaging device, and an electronic circuit. The head orientation sensor is configured for generating an electrical head orientation signal in response to head pitch or head yaw. The eye imaging device is configured for observing an eye feature from the sclera, cornea, iris, or pupil, and generates an eye electrical signal in response to eye position, horizontal eye movement, vertical eye movement, pupil size or eyeblinks at a plurality of times. The electronic circuit is configured for generating an ocular parameter measurement such as saccades, vestibulo-ocular reflex, vestibulo-ocular reflex cancellation, vergence, smooth pursuit, nystagmus, dynamic visual acuity, pupil size, and/or eyeblinks from the head and eye electrical signals. The ocular parameter measurement can be used to determine normal human health, a neurologic disorder, a biochemical health impairment, or a physiologic health impairment.