Hypertropia (Vertical Strabismus)

Hypertropia is a form of strabismus (squint) in which one eye sits higher than the other. It is also called "vertical strabismus" or "vertical squint." The misalignment can be permanent or occur only in certain directions of gaze, and it can lead to double vision, an abnormal head posture, or amblyopia (lazy eye).

Causes

There are various reasons for hypertropia:

• Eye muscle palsy: weakness or paralysis of one of the vertical eye muscles – often the superior oblique muscle (trochlear nerve palsy) – is one of the most common causes. It can be congenital or result from injuries, circulatory disorders, or neurological diseases.
• Congenital miswiring: sometimes the nerve connections to the eye muscles are not correctly formed from birth.
• Brown syndrome: restricted mobility of the tendon of the superior oblique muscle prevents the affected eye from looking up and inward normally.
• Thyroid disease (thyroid eye disease): inflammatory thickening of the eye muscles can cause a vertical misalignment.
• Previous eye muscle surgery: after earlier strabismus surgery, a residual or new vertical deviation can occur.

Symptoms

• Visible vertical deviation of one eye
• Double vision (especially in adults and older children)
• Head tilt to one side (to compensate for the double vision)
• Squeezing one eye shut in bright light
• In children: development of amblyopia if the higher eye is "switched off" by the brain

Diagnosis

The eye examination includes a precise measurement of the eye position in all directions of gaze. Various cover tests and prism measurements show which muscle is affected and how large the deviation is. If a neurological cause is suspected, imaging (MRI) may be necessary.

Treatment

Therapy depends on the cause and extent of the hypertropia:

• Prism glasses: for small deviations, a prism can be incorporated into the glasses to compensate for the double vision.
• Eye muscle surgery: for larger hypertropia or disturbing double vision, the position of the eye muscles is corrected surgically. The goal is to bring the eyes back to the same level.
• Treating the underlying condition: if the hypertropia is the result of another disease (e.g. a thyroid problem), this must also be treated.
• Amblyopia therapy: if a child has reduced vision, additional treatment with a patch or atropine drops is given.

Prognosis

Many forms of hypertropia can be treated well. In children especially, it is important to act early so that vision can develop normally in both eyes and a permanent abnormal head posture is avoided.