Methods for preventing or treating motor-related neurological conditions include using ocular light therapy in connection with a conventional therapy for a motor-related neurological condition, such as a drug regimen, to adjust levels of melatonin and/or dopamine in the body of a subject. The ocular light therapy may include elevated levels of blue-green light or green light (e.g., light within a wavelength range of 460 nm to 570 nm, 490 nm to 570 nm, about 520 nm to 570 nm, etc.). The ocular light therapy may also include reduced levels of amber, orange and/or red light. Methods for diagnosing motor-related neurological conditions include use of ocular light therapy to cause a subject to temporarily exhibit one or more symptoms of any motor-related neurological condition to which the subject is predisposed, or which the subject may already be experiencing. A temporary increase in such symptoms may be effected by ocular administration of light including increased amounts of amber, orange and/or red light.
