What Is Hypertropia?
Hypertropia refers to a vertical misalignment in which one eye is positioned higher than the other. By convention, it is named for the higher eye — a “left hypertropia” means the left eye is elevated relative to the right eye, which is equivalent to a right hypotropia (the right eye is depressed). This distinction matters for surgical planning.
Vertical strabismus is less common than horizontal misalignment but frequently causes significant disability, particularly through vertical diplopia (double vision). The images are vertically displaced, making most tasks requiring binocular vision uncomfortable or impossible.
Causes
Superior Oblique Palsy (4th Nerve Palsy)
The most common cause of isolated vertical diplopia in adults. The superior oblique muscle, which intorts and depresses the eye (particularly in adduction), is weakened by palsy of the fourth cranial nerve. The affected eye sits higher than the fellow eye. Patients often adopt a characteristic head tilt toward the shoulder of the unaffected side to reduce diplopia. The condition may be congenital, post-traumatic, or microvascular in origin.
A distinctive feature is excyclotorsion— the top of the affected eye rotates outward. This can be measured with a double Maddox rod test and may cause a tilted quality to the double vision.
Thyroid Eye Disease
Inflammation and fibrosis of the extraocular muscles — most commonly the inferior rectus — restrict upgaze. The affected eye cannot elevate, making the fellow eye appear relatively elevated (hypertropic by convention). This is a restrictive rather than paretic strabismus.
Skew Deviation
A vertical misalignment caused by a brainstem or cerebellar lesion disrupting otolith-ocular pathways. Characteristically, the three-step test does not localise to a single muscle, and imaging reveals a central lesion.
Dissociated Vertical Deviation (DVD)
An upward drift of one or both eyes that occurs when attention or fixation lapses. It is frequently bilateral, often asymmetric, and is characteristically associated with infantile strabismus. It does not obey Hering’s law.
Other causes include Brown syndrome (restriction of elevation in adduction from a tight superior oblique tendon), orbital disease, and third nerve palsy.
The Parks–Bielschowsky three-step test
Diagnosis
Accurate diagnosis of hypertropia requires a careful ocular motility assessment, including measurement of the deviation in multiple gaze positions and at different head positions. Key investigations include:
- • Prism cover test in primary, left, right, and tilted gaze positions
- • Double Maddox rod test to quantify torsion
- • Hess chart to map the full pattern of motility restriction
- • Forced duction test — passive rotation of the eye to distinguish restriction from paresis
- • Brain imaging for new acquired vertical strabismus without an obvious cause
- • Thyroid function tests and orbital imaging when thyroid eye disease is suspected
Comparing the Three Main Causes
| 4th Nerve Palsy | Thyroid Restrictive Myopathy | Dissociated Vertical Deviation | |
|---|---|---|---|
| Mechanism | Paretic — weakness of the superior oblique muscle causes vertical and torsional deviation | Restrictive — fibrosis of the inferior rectus limits upgaze; contralateral eye appears relatively high | Dissociated — intermittent upward drift of one or both eyes, often exacerbated by inattention |
| Typical patient | History of head trauma, or congenital; any age | Adult with known or suspected thyroid disease; often female | Child with a history of infantile strabismus or other childhood squint |
| Torsion | Excyclotorsion of the affected eye — often measurable with double Maddox rod | Minimal torsion unless multiple muscles involved | No significant torsion |
| Forced duction test | Negative (no restriction) — paretic cause | Positive (resistance to passive elevation) — restrictive cause | Negative |
| Primary surgical approach | Superior oblique tuck; inferior oblique weakening for large DVD component | Inferior rectus recession to release the restrictive force | Inferior oblique weakening; superior rectus recession |
Experiencing vertical double vision?
A prompt assessment is important to identify the cause and determine whether urgent investigation is needed.
Treatment
Treatment is guided by the underlying cause, the angle of deviation, and whether the condition is expected to recover spontaneously.
- Prisms— vertical prisms incorporated into spectacles can neutralise small to moderate hypertropia and provide useful functional relief while awaiting recovery or surgery.
- Observation— for microvascular nerve palsies (from hypertension or diabetes), a waiting period of six to twelve months allows time for spontaneous recovery before surgical decisions are made.
- Superior oblique tuck— shortening of the superior oblique tendon to strengthen the muscle’s depressing and intorting action; the procedure of choice for fourth nerve palsy with a moderate-sized vertical deviation.
- Inferior oblique weakening— recession or myectomy of the inferior oblique is used for fourth nerve palsy when the inferior oblique is overacting, and for DVD associated with inferior oblique overaction.
- Inferior rectus recession— the primary surgical procedure for restrictive hypertropia from thyroid eye disease; releases the fibrotic inferior rectus to restore upgaze.
Sequence matters in thyroid eye disease
Conclusion
Hypertropia is a form of vertical strabismus with several distinct underlying causes. Accurate diagnosis — distinguishing paretic from restrictive from dissociated mechanisms — determines the appropriate investigation, the need for neuroimaging, and the correct surgical procedure. With the right approach, most patients achieve substantial reduction in diplopia and good functional alignment.
Frequently Asked Questions
In most cases of new-onset vertical diplopia in adults, brain imaging is recommended to exclude a serious cause — particularly when a third or fourth nerve palsy is suspected without a clear precipitating cause such as recent head trauma. A sixth nerve palsy in isolation in a patient with hypertension or diabetes may be managed with observation and imaging if recovery is not occurring within the expected timeframe. Your ophthalmologist will guide the appropriate investigation pathway.
Written by
Dr Parth ShahDr Parth Shah is a subspecialty-trained Canberra ophthalmologist with expertise in strabismus surgery, paediatric eye care and cataract surgery.
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