“What causes sudden crossed eyes in adults?”

Hopefully this has not happened to you. In an adult with previously normal eyes with good vision in both eyes, sudden crossing that is persistent (not transient, which could be a drug effect), then double vision will be the result. The causes are many including defects in one of the eye muscles from trauma, or vascular problems in the brain, or tumors in the brain. Other causes include thyroid disease, myaesthenia gravis, multiple sclerosis and a number of rare causes. Whomever this has happened to should quickly see a neurologist or better yet, a neuro-ophthalmologist.

This should not happen. Go to ER or See Ophthalmologist/Neurologist for diagnosis & Treatment.

Unfortunately, there may be several conditions that may cause your problem. I strongly advise you to make an appointment with an Ophthalmologist promptly.

Stroke or rapidly growing brain tumor