The appendages of the eyeball: anatomy and role

The eyelids

Each eye has an upper and lower eyelid, which completely cover the eyeball when brought together. Their role is not only to physically protect the eye, but also to ensure the even distribution of tears (the tear film) through the movements and blinks that sweep the cornea, thus preventing eye dryness and irritation.

Eyelashes are implanted at the edge of the eyelids, and their function is not only aesthetic: they also act as a protective barrier, preventing dirt and dust from entering the eye.

The upper eyelid is much more mobile than the lower. It lifts to open the eye, thanks to the action of the upper eyelid levator muscle. The other eyelid muscle is the orbicularis muscle, which surrounds the eyeball and contracts to close the eye.

Good to know: a deficiency of the levator muscle of the upper eyelid can be responsible for ptosis: the upper eyelid falls too far over the eye. Before undergoing upper blepharoplasty, it is essential that the surgeon identifies this problem and corrects it. Otherwise, the result of the operation will be disappointing.

Depending on the region of the body, the epidermis, the superficial layer of skin, is more or less thick: 2 to 3 millimeters on the soles of the feet or the palms of the hands, but less than 0.5 millimeters on the eyelids. If eyelids are one of the first areas of the face to age, it’s because of this thinness of the skin, combined with the high mobility of the upper eyelid and surrounding tissues (inter-eyelid zone, crow’s feet).

Tear glands

Located in the upper eyelids, the lacrimal glands continuously secrete tears, which spread over the surface of the eye, draining into the tear ducts at the corner of the eye (internal canthus) and finally into the nose. That’s why you need to blow your nose when you cry…

Tears are, of course, mostly water, but they also contain other components (mucus, lipids, proteins, etc.), each of which plays a protective role: it limits water evaporation, helps the tear film adhere to the ocular surface, forms a defensive barrier against microbes, and so on.

Dry eyes may occur in the days following blepharoplasty. If you experience discomfort, instilling tear substitutes (artificial tears) can provide relief while the tear film is reconstituted. Tearing may also occur: this is transitory, most often due to post-operative swelling that prevents tears from flowing normally through the tear duct.

Eyelid abnormalities

Ectropion

Ectropion is an eversion (abnormal protrusion of the mucous membrane) of the free edge of the lower eyelid, which normally covers the eye. The edge, separated from the cornea, exposes the conjunctiva to the action of the air. The result is dry eyes or lacrimation (tears no longer flow properly into the tear duct), chronic irritation and recurrent conjunctivitis.

Ectropion can be present from birth, but more often than not, it’s linked to a loosening of the tissues with age. Chronic conjunctivitis, facial paralysis or poor wound healing may also be involved.

The operation involves raising the lower eyelid to restore contact with the eye and put the eyelashes back in their proper position.

Entropion

This is the opposite of ectropion. The free edge of the eyelid turns towards the eye, the eyelid curls inwards, and the eyelashes rub against the wall of the eyeball, causing a foreign body sensation with every eye movement, irritation and recurrent conjunctivitis. If left untreated, entropion can damage the cornea.

The most common cause is ageing tissue, resulting in a loosening of the eyelid structures. The result is an imbalance in the forces holding the eyelid in place. More rarely, entropion may be congenital or traumatic in origin.

The first thing to do is protect the eye with eye drops and lubricating ointment, but surgery is generally recommended. Several techniques are possible, depending on the nature of the problem. In most cases, the surgeon re-tensions the eyelid and its attachments to correctly reposition the free edge and eyelashes.

In some cases, entropion is due to hyperactivity of the orbicularis muscle, combined with tissue laxity. In this configuration, known as spasmodic entropion, Dr. Hayot recommends Botox injections to weaken the orbicularis muscle.

Ptosis

Ptosis, also known as “palpebral ptosis” or “blepharoptosis”, is a drooping of the upper eyelid resulting from a deficit in the levator muscle of the upper eyelid. It may be unilateral or bilateral.

The visual field may be reduced, as may vision when the eyelid covers part of the pupil. Depending on the degree of drooping, a distinction is made between minimal, moderate and severe ptosis.

Deficiency of the eyelid levator muscle may be congenital (present from birth), due to an abnormality of this muscle. It can also be acquired, following trauma or a neurological or muscular disorder. Muscular laxity is also linked to ageing, as the eyelid lift muscle gradually becomes deinserted, causing the eyelid to droop.

The procedure depends on the cause of the ptosis. It often involves shortening the levator muscle of the upper eyelid, then refixing it to restore the visual field.

In the majority of cases, the results are convincing, but symmetry and good eyelid function are not always achievable. Operating on an abnormal muscle is delicate, and hyper- or hypocorrection are possible phenomena.

After ptosis surgery, a temporary inocclusion (eyelid closure defect) is common, but improves rapidly.