The appearance that one eye is lower than the other is a common concern, pointing to causes ranging from natural variations to underlying medical conditions. Subtle facial asymmetry is normal, but a noticeable difference in eye height is often due to issues with the eyelid position, the bony structure of the face, or the muscles and nerves controlling the eye. This vertical misalignment, known clinically as vertical dystopia, can involve the entire eyeball or just the surrounding soft tissue. Understanding the source is the first step toward proper evaluation.
Differences in Eyelid Position
The simplest explanation for a lower eye is a difference in the height of the upper eyelid margin, known as ptosis (a droopy eyelid). Ptosis makes the eye opening appear smaller and lower, even if the eyeball is perfectly aligned.
The most frequent cause of acquired ptosis in adults is the gradual stretching or separation of the levator aponeurosis, the tendon-like structure connecting the eyelid-lifting muscle to the eyelid plate. This age-related change is known as aponeurotic ptosis, where muscle function is preserved but the attachment point has weakened.
Ptosis can also be congenital, resulting from a developmental malformation of the levator muscle that fails to lift the eyelid fully. Other causes include muscle disorders like Myasthenia Gravis, mechanical factors such as an eyelid tumor or significant swelling, or pseudoptosis, where a lower eyebrow pushes the upper eyelid down.
Structural Causes Involving the Orbit and Facial Bones
When the entire eyeball is positioned lower, the cause typically relates to the physical structure of the bony eye socket, or orbit. This true vertical orbital dystopia involves a change in the volume or shape of the bony container holding the eye.
Trauma is a frequent cause, particularly a “blowout fracture” of the orbital floor or medial wall. A fracture creates an opening allowing orbital fat and soft tissue to shift into adjacent sinuses, increasing the orbit’s volume.
Because the eye volume remains constant, this increased internal space causes the eye to sink backward (enophthalmos) and often downward (hypoglobus). Aging also contributes to structural asymmetry, as bone resorption expands the orbital rim, and fat loss results in a sunken appearance. Developmental differences in orbital bone size and position from birth can also cause mild, non-pathological asymmetry.
Neurological and Muscular Explanations
Discrepancy in eye height can signal a problem with the extraocular muscles or the nerves that control them. One of the most common disease-related causes is Graves’ orbitopathy (Thyroid Eye Disease or TED), an autoimmune condition causing inflammation and swelling of the eye muscles and orbital fat. This inflammation leads to a restrictive myopathy, making the enlarged muscles stiff and preventing free eye movement.
The inferior rectus muscle, which moves the eye down, is most frequently affected. When this muscle becomes scarred and fibrotic, it shortens and pulls the eye downward, resulting in fixed hypotropia (downward misalignment).
Furthermore, a palsy of the fourth cranial nerve (the trochlear nerve) can cause vertical misalignment. This nerve controls the superior oblique muscle, which depresses and intorts the eye. Damage to this delicate nerve disrupts coordination between the eyes and often results in binocular vertical double vision.
When Asymmetry Requires Medical Attention
While mild facial asymmetry is normal, any sudden or noticeable change in eye position requires professional evaluation. Symptoms like the acute onset of double vision (diplopia), especially vertical separation of images, suggest a new problem with the eye muscles or nerves.
Urgent “red flags” include:
- Eye pain.
- Rapid or progressive bulging of one eye (proptosis).
- Changes in the size or reactivity of the pupil.
- New asymmetry following a recent head or facial injury.
A physician must determine if the issue is a cosmetic eyelid problem or a deeper orbital or neurological condition. The initial step is typically an evaluation by an Ophthalmologist to examine eye movement and alignment. Depending on the suspected cause, an Oculoplastic Surgeon may be consulted for eyelid and orbital structure issues, or a Neurologist may be involved if a cranial nerve palsy or neurological disease is suspected. Timely diagnosis is important because conditions like Graves’ orbitopathy or an impending stroke benefit from early intervention.