What Is Hypertropia?

Hypertropia is a type of vertical strabismus (crossed eyes) where one eye is deviated upwards compared with the other eye. This can happen all the time or intermittently. Hypertropia occurs when the muscles in both eyes are not balanced and working together. The condition, which can affect both adults and children, is triggered by a wide range of reasons, including nerve palsies, stroke, thyroid disease, trauma, and neurological disorders. Intermittent types of hypertropia are usually a result of stress or tiredness.

This condition does not disappear on its own and requires treatment. The most common ways to treat it are with glasses, patches, vision therapy, or surgery. Earlier detection and treatment are associated with better outcomes for people with hypertropia.

Hypertropia Symptoms 

The most noticeable symptom of hypertropia is that one eye moves upwards relative to the other eye. However, if the problem is not permanent, it can go unnoticed. In some cases, it will only appear when the person is tired or under a lot of stress.

Symptoms may vary depending on the cause of a person's hypertropia, but can include:

• Double vision (diplopia): Commonly, people with hypertropia will have double vision since the eye will struggle to focus and may duplicate the images.
• Tilting head: Children with hypertropia will often tilt their heads to one side to eliminate the double vision that hypertropia frequently causes.
• Headaches
• Eye strain
• Pain above the eyebrow

Causes

Hypertropia is most commonly caused by problems with eye muscles, which are usually triggered by different neurological conditions or eye injury.

The causes of hypertropia include:

• Fourth cranial nerve palsy: The fourth cranial nerve (CN IV), also known as the trochlear nerve, is one of the nerves that control the superior oblique muscle, which is responsible for eye movement. Fourth cranial nerve palsy means a certain muscle in the eye is paralyzed, which causes the eye to have an upward drift. It is caused by disease or injury to the fourth cranial nerve. In children, it is most often present at birth (congenital). In adults, it is most often caused by injury that involves whiplash or concussions. It can also be a result of poor blood flow related to diabetes. Some cases go away on their own, but others need surgery to correct the problem.
• Brown's syndrome: This is a rare condition where the superior oblique muscle malfunctions and is unable to freely pass through the trochlea, and the affected eye is held down by the muscle. The main symptom is misalignment of the eyes, which can be looking upwards or toward the nose. It is most commonly in only one eye, usually the right eye. People can be born with it or develop it during life, which happens less frequently. More severe cases will require surgery.
• Stroke: Vision is often affected after a stroke. The blood clots that led to a stroke can also damage the nerves responsible for eye movement, resulting in hypertropia in some cases.
• Thyroid eye disease: Also known as Graves' orbitopathy, this condition is mainly associated with hyperthyroidism. The etiology for hypotropia associated with thyroid eye disease is due to a restrictive strabismus that is a result of the thickening or scarring of the inferior rectus muscle, which depresses the eye. Thyroid eye disease leads to multiple ophthalmologic issues, including three types of strabismus. It can happen at any stage of life, but is more common in people who are 45 years of age or older. The most common way to fix it is with surgery. Smoking, thyroid dysfunction, and a family history of thyroid eye disease are known risk factors.
• Eye injury: Extraocular muscle traumas can cause the eyes' misalignment and different types of strabismus, including hypertropia.

Diagnosis

An optometrist or ophthalmologist can diagnose hypertropia. An eye exam is the first step toward figuring out the diagnosis. However, the final results can be misleading, especially in people with more than one muscle that is paralyzed or who have gone through strabismus surgery.

Your eye care provider will also conduct a number of ocular deviation tests to assess your eyes for hypertropia, including:

• Hirschberg test: Also known as the corneal light reflex test, it checks ocular alignment. During this test, a light source is directed at a person's eyes, and they are asked to fixate on the light source directly. The corneal light reflex is then observed. It is considered normal when the corneal light reflexes are slightly de-centered nasally. In the case of hypertropia, the light reflex of the deviated eye is located below the light reflex of the fixing eye.
• Krimsky test: This test complements the Hirschberg test. When conducting this test, a prism is placed in front of the deviating eye until the corneal reflex is re-centered in the pupil. The result shows the amount of deviation.
• Cover/uncover test: During this test, your eye doctor will briefly cover the eye that is fixing (maintaining visual gaze on a single location) and see if there is a refixation movement of the fellow eye. In hypertropia, the non-fixating eye moves downward as it takes up fixation.
• Simultaneous prism cover test: This test is performed by placing a prism that is oriented in the appropriate direction for the deviation over the non-fixating eye while covering the fixing eye until there is no shift in fixation or the deviation is neutralized. This test is used to neutralize the deviation.

For children, doctors will often catch hypertropia when they notice that their eyes are misaligned during well-baby checkups. It is essential to let the professional know if there is family history of eye problems. 

Treatment

Hypertropia can be treated in a few ways:

• Surgery: This is the most common way to correct hypertropia. An ophthalmologist can loosen, tighten, or move certain eye muscles so that the eyes line up properly to work together.
• Glasses:  People with hypertropia often have double vision, and doctors may prescribe prism glasses to correct the problem. A prism used in eyeglasses bends light before it travels through the eye. The light is redirected so it will fall correctly on the retina in each eye and the person will just see one image.
• Eye patch: An eye specialist may also ask someone with hypertropia to cover the healthy eye with an eye patch to force the affected eye to work correctly.
• Vision therapy: It aims to improve communication between the brain and the eyes. It is often combined with other treatments, and an eye care specialist should always guide them. This is usually used in conjunction with corrective lenses.

A Word From Verywell

Hypertropia is not a common problem, but it can be easily treated with proper glasses, eye patches, and surgery. It mostly commonly presents in young children but can affect adults later in life after an injury. When you notice any vision changes, you should contact your eye care professional and have your eyes checked for any issues. This way, it is possible to catch and treat any possible eye issues early.