Dr. Brian Joondeph, a retina surgeon, explains what probably is going on:

Eye movement is controlled by six muscles attached to each eye, allowing eyes to move up, down, diagonally, and rotationally. These muscles are in turn controlled by a combination of three cranial nerves originating in brain stem, an area between the brain and spinal cord, then travelling upward to the eyes.

Mrs. Clinton’s original trauma and blood clot likely damaged at least one of her cranial nerves. During Congressional testimony over Benghazi, she was wearing eyeglasses with Fresnel prisms, used to correct double vision due to eye misalignment. But that was four years ago. Why are her eye movements still misaligned?

Synkinesis is a condition where nerves rewire incorrectly after trauma. This may cause one eye to look left or not move at all when the brain tells it to move right. Smiling or chewing may cause the eyes to move, which would explain Mrs. Clinton’s abnormal eye movements while giving a recent speech.

Funny eye movements alone are no big deal. Many people have a crossed eye, called strabismus, due to a childhood lazy eye, previous eye injury or surgery, or a small stroke of one of the cranial nerves. But in Mrs. Clinton’s case, there are other worrying signs, including possible seizure activity, her recent collapse, coughing fits, all on top of her history of head trauma, blood clot, and ongoing anticoagulation therapy.