Our eyelids serve a few functions. One is to protect the delicate eye from dirt, debris, and even incoming projectiles such as a wayward snapped rubber band. Another function is to keep the surface of the eye well lubricated for the purposes of both eye health and good vision by containing various glands that secrete the multiple components of our complex tear film.
When the eyelids don’t function as they should, such as with an eyelid ptosis, it can impact various aspects of our vision, such as hindering the sight out of the affected eye or inducing dry eye. Some of these cases are age-related and may simply require referral to a specialist in oculoplastic surgery while other ptosis causes are a sign of a more serious underlying disease that necessitates further medical investigation.
What is an Eyelid Ptosis?
A ptosis is the medical term for a drooping upper eyelid. The magnitude of the ptosis can vary from being only noticeable when carefully comparing the height of the eyelid to the other eye, to being severe enough such that the eye appears almost entirely closed and ptosis surgery is required to restore vision.
The most common cause of an eyelid ptosis is simply age, a condition termed aponeurotic ptosis or senile ptosis. The action of the upper eyelid is controlled mainly by a muscle called the levator palpebrae superioris, which is anchored to the surrounding tissues by a ligament. With time, age, and gravity, this ligament can stretch and loosen or become entirely detached, resulting in a limited ability to hold up the eyelid levator muscle. An aponeurotic ptosis is generally easily rectified through ptosis surgery in a procedure that aims to either shorten the levator muscle or reattach the ligament. If uncorrected with oculoplastic surgery, an age-related ptosis can worsen with time.
In addition to occurring in the elderly, an eyelid ptosis can also occur in the very young, as is the case in a congenital ptosis. During this condition, an infant is born with an existing ptosis, most commonly due to underdevelopment of the eyelid levator muscle. A congenital ptosis will rarely worsen with time if left uncorrected, however, if the drooping eyelid is low enough to obscure vision, the ophthalmologist will likely recommend ptosis surgery early in life to encourage proper visual development in the eye and avoid causing a lazy eye (amblyopia).
Localised diseases or conditions of the eye can also contribute to ptosis causes. These include infections of the eyelid, which causes inflammation and swelling, or the presence of some lesion that physically weighs down the upper lid, causing it to droop. Such lesions can be a simple chalazion or stye, or may be more serious such as a large tumour. Trauma to the eye area can also induce a ptosis, such as eyelid swelling from a black eye.
Rarely, ptosis causes can be the result of a more serious disease requiring medical attention beyond an oculoplastic surgery specialist. One of these conditions is myasthenia gravis, which is an autoimmune neuromuscular disease resulting in muscle weakness. Myasthenia gravis is characterised by a worsening of muscle fatigue and weakness after periods of activity, improving after periods of rest. Often, deterioration of the muscles around the eyes may be one of the first signs of myasthenia gravis, including a ptosis but also the presence of double vision as the muscles that control the movements of the eyeballs themselves fatigue (ocular myasthenia).
When presenting with a ptosis, if the doctor suspects myasthenia, he or she may test this by asking the patient to look upward for a sustained period of time; a person with myasthenia gravis will find the ptosis worsens during this activity. Unfortunately, there is no current cure for myasthenia, but with modern medicine there are many therapies available that can effectively improve muscle function and quality of life for affected individuals. For some people, ptosis surgery can be a useful treatment in addition to medical management for the systemic disease.
Another cause of ptosis can arise from problems with the nerves that control the eyelid muscles. The upper eyelid is innervated by the third (out of 12) cranial nerves. Any condition that affects the pathway of this nerve through the brain can result in a ptosis, including diseases such as a stroke, brain tumour, or aneurysm in the brain. Even long-term diabetes has the potential to cause nerve damage.
A rare condition known as Horner’s syndrome can present with a ptosis, double vision, and abnormally small pupil, due to damage to one section along a chain of nerves that run from the brain, down the spinal cord to the top of the lungs, and then back up the neck to the face. Causes of Horner’s syndrome that may result in a ptosis include a lung tumour, a stroke in the brainstem, birth trauma to the neck and shoulder, or injury to the carotid artery. If the doctor suspects Horner’s syndrome, ptosis surgery will not be a priority – instead, you will most likely be sent to the hospital emergency department.
Be reassured that most cases of ptosis are benign and simply a result of age. However, should you notice an eyelid progressively becoming more and more droopy, it is important to be assessed by an appropriately experienced eye specialist.