Hypertropia is a form of strabismus (eye misalignment) involving a vertical deviation, where one eye turns upward compared to the other. This condition results from an imbalance in the eye muscles, preventing them from working together to point in the same direction. Hypertropia affects both children and adults and can be constant or appear intermittently, especially during fatigue or stress.
Identifying Hypertropia
The most apparent sign of hypertropia is the visible upward turn of one eye. This misalignment can be subtle, only becoming noticeable when an individual is tired or stressed. In other instances, the unaffected eye may appear to point downward while the affected eye looks straight ahead.
This lack of coordination disrupts the brain’s ability to merge two images into a single view, frequently leading to double vision (diplopia). To compensate and eliminate double vision, individuals often adopt a characteristic head tilt to align the images from both eyes. Persistent effort to control the misalignment can also lead to eye strain, fatigue, and headaches.
Underlying Causes of Vertical Misalignment
Hypertropia arises from issues with the muscles and nerves that govern eye movement. A frequent cause is weakness or paralysis in one of the extraocular muscles responsible for moving the eyeball. Palsy of the fourth cranial nerve is a common factor, as it controls the superior oblique muscle, which helps rotate the eye downward. When this nerve is damaged, the muscle cannot function properly, leading to an upward drift of the eye.
Trauma to the head or face can also cause hypertropia by injuring the eye muscles or the bones of the eye socket (orbit). This can physically restrict eye movement or damage the nerves controlling the muscles. Thyroid eye disease, an autoimmune condition, can cause eye muscles to swell and stiffen, impairing their movement. Hypertropia can also be congenital, present at birth due to developmental anomalies.
Diagnosis and Treatment Pathways
An ophthalmologist or optometrist diagnoses hypertropia through a comprehensive eye examination. The process involves tests to assess alignment, such as the cover-uncover test. During this test, the doctor has the patient focus on an object while covering and uncovering each eye to observe any deviation. Prism and cover tests are also used to measure the magnitude of the eye’s vertical deviation.
Based on the diagnosis, a treatment plan is developed to align the eyes and reduce strain. For some individuals, non-surgical options are effective. Eyeglasses with a prism can bend light to help merge the two images into a single view. Vision therapy, a series of exercises to improve eye coordination, may also be recommended.
In more significant cases of misalignment, surgery may be recommended to adjust the tension of the eye muscles by loosening, tightening, or repositioning them. Timely treatment is important for preventing amblyopia (“lazy eye”), a condition where the brain ignores the image from the misaligned eye. Proper treatment also helps restore depth perception.