hypertropias

Hypertropia is a form of vertical strabismus in which one eye is elevated relative to the other in primary gaze. It can be constant or intermittent and may produce binocular diplopia or sensory suppression. Hypertropia is distinguished from hypotropia, where the affected eye drifts downward. The term can describe an isolated vertical misalignment or part of a broader motility disorder.

Causes and classification. Hypertropia can be paralytic, due to dysfunction of a vertical extraocular muscle or its nerve supply (for example, superior oblique palsy from cranial nerve IV, or inferior rectus or other muscle involvement from cranial nerve III or VI lesions). Nonparalytic hypertropias arise from muscle overaction or underaction, contracture, or mechanical restriction, including thyroid eye disease, orbital trauma, or decompensation of a congenital vertical deviation. Skew deviations (central or brainstem causes), myasthenia gravis, and anisometropia-related sensory misalignment can also contribute. Hypertropia may be constant or intermittent, and can be unilateral or alternating between eyes.

Diagnosis and evaluation. Evaluation includes a thorough eye exam with cover tests to measure the vertical deviation at distance and near, assessment of eye movements, and documentation of head posture. The Bielschowsky three-step test helps localize the involved cyclovertical muscles by evaluating changes with gaze direction and head tilt. Additional workup may include neuroimaging or laboratory testing if a neurologic or systemic cause is suspected.

Treatment and prognosis. Management is etiologic. Small, asymptomatic hypertropias may be observed or corrected with prisms. Diplopia or functional impairment is often addressed with prisms, occlusion, or vision therapy in selected cases. When nonoperative measures fail or are unsuitable, strabismus surgery or botulinum toxin injections to adjust the vertical muscles may be employed to realign the eyes. Prognosis depends on the underlying cause and response to treatment; congenital or stable cases may require multiple interventions, whereas some paralytic hypertropias improve over time.