The technique has been approved for the treatment of depression, and is being tested against several other conditions, including Parkinson’s disease and migraines.

The doctor or mental health care provider can do an exam to help determine if you have depression or if you have another health or mental health problem.

They did the tests on healthy subjects and on patients with depression. Turns out that depressed people have much lower retinal responses-even if they're on antidepressants.