1. Nonparalytic hypertropia

 A. Abnormal insertion of muscles
 B. Abnormal fascial attachments
 C. Complications of systemic diseases, such as myasthenia gravis, thyrotoxicosis, and orbital tumors

2. Paralytic hypertropia-isolated cyclovertical muscle palsy

 A. Brainstem disease
 B. Fourth nerve palsy
 C. Multiple sclerosis
 D. Skew deviation
 E. Third nerve palsy

3. Double hyperphoria (alternating circumduction)-fuses, but cover test shows alternating hyperphoria
4. Apparent paralysis of elevation of one eye

 A. Local neuromuscular and orbital causes
  (1) Dysthyroid ophthalmoplegia (noncongestive and congestive form)
  (2) Myasthenia gravis (Erb-Goldflam syndrome)
  (3) Orbital floor fracture
  (4) Progressive supra nuclear ophthalmoplegia
  (5) Oculomotor nerve paresis superior division
  (6) Unilateral double-elevator palsy, congenital dysfunction of superior    rectus and inferior oblique muscles
  (7) Myositis
   a. "Collagen diseases"
   b. Infectious myositis
   c. Trichinosis
  (8) Orbital tumors
   a. Dermoid cyst
   b. Hemangioma
   c. Lymphoma
   d. Meningioma
   e. Optic nerve glioma
   f. Previous strabismus surgery
   g. Rhabdomyosarcoma
  (9) Systemic amyloidosis with ocular muscle infiltration
  (10) Vertical retraction syndrome (Parinaud syndrome)
  (11) Superior oblique tendon sheath syndrome (Brown syndrome)
 B. Skew deviation due to a central nervous system lesion-one eye is above the  other; may be  the same for all directions of gaze or vary in different directions of  gaze
  (1) Unilateral labyrinthine disease
  (2) Cerebellar tumors, such as astrocytomas and medulloblastomas
  (3) Acoustic neuromas
  (4) Vascular accidents of pons and cerebellum, such as thrombosis of    cerebellar and pontine arteries
  (5) Unilateral internuclear ophthalmoplegia and less frequently bilateral    internuclear ophthalmoplegia
  (6) Compressive lesions, such as platybasia and Arnold-Chiari     malformation
  (7) Brain-stem arteriovenous malformations
  (8) Aberrant regeneration of third nerve
 C. Central nervous system lesions
  (1) Arteriosclerosis, thrombosis, arteritis (syphilitic), or embolus of fine    vessels to midbrain

5. Apparent paralysis of elevation of both eyes

 A. Physiologic in older persons
 B. Parinaud syndrome (divergence paralysis)
 C. Chronic progressive external ophthalmology (CPEO)
 D. Progressive supranuclear palsy
 E. Myasthenia gravis
 F. Midbrain lesion
  (1) Upgaze center
  (2) Bilateral third nerve palsy
  (3) Dorsal midbrain syndrome
 G. Congenital fibrous syndrome
 H. Thyroid myopathy
 I. Metastatic tumor (breast cancer)

6. Paralysis of downward gaze

 A. Reverse Parinaud syndrome
 B. Associated with choreoathetotic syndromes
 C. Parkinsonian syndromes
 D. Myasthenia gravis
 E. Miscellaneous

Flaherty MP, et al. Congenital fibrosis of the extraocular muscles associated with cortical dysplasia and maldevelopment of the basal ganglia. Ophthalmology 2001; 108:1313-1322.

Keane JR. Ocular skew deviation. Arch Neurol 1975; 32:185.

Metz HS. Double elevator palsy. J Ped Ophthal Strab 1981; 18:31-36.

Kushner BJ. Errors in the three-step test in the diagnosis of vertical strabismus. Ophthalmol 1989; 96:127-132.