Causes of a Drooping Eyelid on One Side
A drooping eyelid on one side (unilateral ptosis) is when only one of the upper eyelids sits lower than the other. The difference between the two eyes is often noticeable from the outside and can give the face an asymmetric, tired expression. A droop affecting one eye should not be regarded only as a cosmetic problem; especially if it has developed later in life, the underlying cause should be investigated.
What Causes a Drooping Eyelid on One Side?
A one-sided droop present from birth is mostly caused by the muscle that lifts the eyelid (the levator muscle) not developing sufficiently on that side. The main causes of a one-sided droop that develops later are:
- Loosening of the connective tissue by which the muscle attaches to the lid, due to age, long-term contact lens wear or previous eye surgery
- Blows and injuries to the eyelid
- Involvement of the nerve that controls the muscle that lifts the eyelid: diabetes and high blood pressure can impair the function of this nerve; more rarely, pressure inside the skull or a blood vessel problem may be involved
- Conditions such as Horner syndrome that affect the pupil and the eyelid together
- Diseases with muscle fatigue, such as myasthenia gravis
- Masses, swelling or scar tissue on the eyelid
- A temporary droop after botulinum toxin treatments around the eyes
Symptoms
The most obvious sign is the difference in height between the two upper eyelids. To see better, the person may raise the eyebrow on the drooping side or tilt the head back, which can lead to forehead lines and headaches. If the droop covers the pupil, the field of vision narrows. If it is accompanied by double vision, a difference in pupil size or restricted eye movements, or if the droop started suddenly, a doctor should be seen urgently.
Diagnosis
The diagnosis is made by examination. The doctor asks when the droop started and, if necessary, compares old photographs. The height of the lid, the strength of the muscle that lifts the eyelid, eye movements and the pupils are assessed. If a disease is suspected, a neurological assessment, blood tests or imaging may be requested. In some people, a marked droop on one side can hide a mild droop of the other eyelid; for this reason both eyes are assessed together.
Treatment
If there is an underlying disease, its treatment is planned first. For a permanent droop or one that affects vision, the treatment is surgery, and the method is chosen according to the strength of the muscle:
- If the muscle is strong enough, the lid is raised by shortening or reattaching the muscle that lifts the eyelid or its connective tissue.
- If the muscle is very weak, the eyelid is connected to the forehead muscle with a thin sling material.
In a one-sided droop, the aim is to reduce the difference between the two eyes; however, perfect symmetry cannot always be achieved and an additional correction may be needed. Swelling and bruising are expected after surgery. The risks include the lid being raised more or less than expected, being unable to close the eye fully and dry eye, infection and bleeding. Exercises or natural remedies suggested on the internet do not correct a drooping eyelid.
A Drooping Eyelid on One Side in Children
In children, a one-sided droop that covers the pupil can affect visual development and lead to a lazy eye. For this reason, early assessment by a children's eye specialist is important. When vision is threatened, surgery may be planned at an early age; in milder cases regular follow-up is carried out and the timing of surgery is decided together with the doctor. Under the age of 18, surgery may be performed only for correctable functional impairments, when the doctor considers it appropriate and with the consent of the legal guardian.
For the general causes and treatment of a drooping eyelid you can read our articles What Causes a Drooping Eyelid? and Drooping Eyelid (Ptosis): What Is It and How Is It Treated?.
Author: Op. Dr. Yücel Sarıaltın