1. Functional

 A. Convergence insufficiency
 B. Exophoria
 C. Exotropia
 D. Hysteria
 E. Poor attention span

2. Organic

 A. Brain lesion, to include bilateral occipital lobe lesions, superior colliculi, and  anterior internuclear ophthalmoplegia, such as in hemorrhage, trauma, or tumors
 B. Dorsal midbrain syndrome
 C. Encephalitis
 D. Exophthalmic goiter-Möbius sign
 E. Exophthalmos
 F. Multiple sclerosis
 G. Myotonic dystrophy
 H. Narcolepsy
 I. Poor visual acuity in one or both eyes
 J. Postencephalitis
 K. Syphilis and tabes
 L. Third nerve paralysis (see p. 153)
 M. Whiplash injury

3. Drugs, including the following:
 

alcohol allobarbital amobarbital amphetamine aprobarbital barbital bromide bromisovalum butabarbital butalbital butallylonal butethal carbamazepine carbon dioxide chloral hydrate

cyclobarbital cyclopentobarbital dextroamphetamine dimethyl tubocurarine iodide diphenylhydantoin floxuridine fluorouracil heptabarbital hexethal hexobarbital mephobarbital methamphetamine metharbital methitural methohexital

metocurine iodide morphine opium penicillamine pentobarbital phenmetrazine phenobarbital phenytoin primidone probarbital secobarbital talbutal thiamylal thiopental tubocurarine vinbarbital

Fraunfelder FT, Fraunfelder FW. Drug-induced ocular side effects. Woburn, MA: Butterworth-Heinemann, 2001.

Walsh FB, Hoyt WF. Clinical neuro-ophthalmology, 4th ed. Baltimore: Williams & Wilkins, 1985.