Ophthalmology: Eyelid problems

In the fifth part of their series, Sophia Pathai and Andrew McNaught take you through problems with the eyelid

Although ophthalmic examinations concentrate mostly on the globe of the eye, you should also pay attention to the eyelids. Lid problems can vary from chronic common conditions to providing important signs of life threatening pathology.

Basic eyelid anatomy

It's worth being aware of some basic eyelid anatomy so that you can try to work out where the problem lies. From superficial to deep, the eyelid consists of skin, subcutaneous tissue, the obicularis oculi muscle, the orbital septum (a membranous sheet continuous with the periosteum), tarsal plates, smooth muscle, and finally, conjunctiva. The upper lid also receives the insertion of the levator palpebrae superioris muscle which raises the lid.

The skin is thin and contains many sebaceous glands and small sweat glands. Remember that dermatological problems can also affect the skin of eyelids. The obicularis oculi muscle is important in facial expression, and contraction of the muscle closes the eyelids; its nerve supply is from the temporal and zygomatic branches of the facial nerve. The orbital septum is a fibrous sheet that originates from the orbital periosteum and serves as a barrier between the orbit and the eyelid to limit the spread of infection and bleeding. The levator muscle originates in the apex of the orbit and contains a muscular portion about 40 mm long and an aponeurosis 14-20 mm long.

Dehiscence of this aponeurosis is an important cause of acquired ptosis (drooping of the eyelid). The levator muscle is supplied by the oculomotor (third cranial) nerve. Just underneath the levator is the superior tarsal muscle (Muller's muscle); it provides a further 2 mm elevation of the eyelid and is sympathetically innervated. The tarsal plates consist of dense connective tissue and give support and strength to the eyelids; they also contain the meibomian glands, which produce secretions that contribute to tear film. The conjunctiva forms the posterior layer of the eyelids and contains accessory lacrimal glands and goblet cells that secrete mucin.

Eyelid malposition

Ptosis

Ptosis is drooping of the upper eyelid when the patient is looking straight ahead. Upper lid position and contour varies with race, but generally the lid covers 2 mm of the cornea at the vertical position. The ptosis may be unilateral or may affect both eyes. Ptosis is usually described as congenital or acquired; although useful for revising for exams, a more practical division that is helpful when you are faced with a patient on the ward is based on the cause of the ptosis (see box).

Acquired ptosis

Important diagnoses to exclude when examining a patient with a ptosis are acquired Horner's syndrome and third cranial nerve palsy as these may have important, or even life threatening associations. Horner's syndrome may be congenital or acquired and is due to interruption of the sympathetic nervous chain. This causes a mild ptosis (remember that Muller's muscle is responsible for 2 mm of lid elevation), anhidrosis (lack of sweating), and miosis (pupillary constriction) on the involved side. In congenital cases the iris may be paler on the affected side. Any lesion that affects the sympathetic outflow pathway from the brainstem to the third order (postganglionic) neuron can cause a Horner's syndrome. Sinister causes include apical (Pancoast) lung tumours, and aneurysm or dissection of the carotid artery. A variety of pharmacological tests can ascertain where the problem lies in the sympathetic chain.

Third cranial nerve palsies may be vasculopathic or compressive. The third cranial nerve runs a long course originating at the midbrain, then running lateral and parallel to the posterior communicating artery, and eventually to the superior orbital fissure in the orbit, joined by parasympathetic fibres from the ciliary ganglion. The nerve supplies the extraocular muscles (except the superior oblique and lateral rectus), the levator muscle, and, via the parasympathetic fibres, the sphincter muscle of the pupil. Most third nerve palsies are vasculopathic in origin and are associated with underlying diabetes, hypertension, or atherosclerosis. This type of acquired palsy does not usually cause a complete ptosis or pupillary abnormalities; the palsy often resolves spontaneously within three months. In stark contrast, a potentially life threatening cause of a compressive third nerve palsy is an aneurysm of the posterior communicating artery. This type of palsy often, but not always, presents with a complete ptosis and a fixed dilated pupil. The patient may also give a history of preceding headache. Always have a low threshold for suspecting a compressive third nerve palsy and never assume that a pupil sparing palsy with a partial ptosis is solely due to microvasular disease; compressive palsies can evolve over time from hours to days. Prompt neurosurgical referral and imaging is essential.

Entropion

An entropion is a turning in of the eyelid and more commonly affects the lower lid. Most entropions are involutional (age related), but there are other causes including trauma and chemical burns. The inverting lid causes lashes to rub on the conjunctiva and cornea leading to a foreign body sensation, redness, and watering. Temporary measures to relieve the symptoms include taping of the eyelid to evert the margin, but ultimately surgery is needed.

Ectropion

In ectropion, the eyelid turns outward. Symptoms are related to pooling of tears due to loss of eyelid apposition to the globe. In more pronounced cases, chronic conjunctival inflammation can lead to hypertrophy and keratinisation of the conjunctiva. The commonest cause of ectropion is involutional change. Mechanical traction on the lid--for example, from lower lid tumours--can also lead to an ectropian. Another important cause that you may see on general medical wards is neurological disease (most commonly a cerebrovascular accident) that affects the seventh cranial nerve which supplies the obicularis muscle. Incomplete eyelid closure can compromise normal lid and tear function, and this can lead to damage to the cornea in the form of an exposure keratopathy. Adequate lubrication of the cornea by means of artificial tears and lubricating ointment are necessary to prevent corneal damage; in some cases surgery is required to reduce exposure (tarsorraphy).

Entropian

Eyelid retraction This is present when the upper or lower eyelid position is displaced, exposing the sclera between the corneoscleral limbus and the eyelid margin. Thyroid eye disease (Graves's disease) is the most common cause of retraction of both the superior and inferior lid. Although thyroid eye disease is typically associated with hyperthyroidism, patients may be hypothyroid or euthyroid. Lid retraction can result in failure of complete closure of the lids (lagophthalmos), leading to ocular irritation and potential damage to the cornea.

Infection and inflammation

Preseptal and orbital cellulitis

Preseptal cellulitis refers to infection and inflammation confined to the eyelids and structures anterior to the orbital septum. Lid infections are not life threatening as the orbital septum prevents further spread of infection (although untreated preseptal cellulitis can extend through the septum). In contrast, in orbital cellulitis there is infection of the orbital soft tissue posterior to the orbital septum. This is a potentially life threatening condition as extension direct to the brain is possible. To be able to differentiate between preseptal and orbital cellulitis is, therefore, essential.

Preseptal cellulitis presents with a tender, erythematous, and swollen eyelid. The globe is uninvolved, which means that the acuity, pupillary reactions, and ocular motility should all be normal. In children, the commonest cause of a preseptal cellulitis is underlying sinusitis; in teenagers and adults the source of infection often arises from a superficial source such as an infected chalazion (see below) or lid laceration. Orbital cellulitis presents in a similar way with a red, tender eyelid, but also with additional systemic and local features. The patient may feel generally unwell and may be pyrexial. The globe may be protruded forwards (proptosis) and reddened (chemosis), with restriction or pain of extraocular movements. Decreased vision and pupillary abnormalities (be sure to examine for a relative afferent pupillary defect) suggest optic nerve compression and orbital involvement of infection. Orbital cellulitis most often occurs secondary to direct spread from an adjacent sinusitis; however, trauma and intraorbital surgery are also important causes to exclude when taking a history. Treatment is aggressive with intravenous antibiotics and surgical drainage if necessary; in comparison a preseptal cellulitis will usually settle with oral antibiotics.

Chalazions and styes

A chalazion results from a blocked meibomian gland. As mentioned, these glands are sebaceous glands and are located in the tarsal plate that produces oil; so these lesions are found close to the edge of the eyelid, and can affect both the upper and lower lid. The blocked contents of the gland set up an inflammatory response within the tarsus and soft tissue manifesting as a small red tender lump. Chalazia usually resolve spontaneously over a period of months, but, in the acute stages, warm compresses can help to reduce the inflammation. Sometimes, chalazia can become chronic and cyst-like, requiring surgical excision. Occasionally, chalazia can become secondarily infected, and lead to a preseptal cellulitis. A stye is an infected eyelash follicle. Their natural history is to resolve spontaneously over about a week. They only rarely progress to a superficial cellulitis.

Eyelid lesions

Eyelid tumours most commonly develop from the epidermis, although they can also arise from the hair follicles, sweat glands, or lacrimal apparatus. Benign epithelial lesions include seborrhoeic keratoses and papillomas, which also occur elsewhere on the body. The most common malignant disease of the lids is basal cell carcinoma. They are often located on the lower lid margin near the medial canthus. The common clinical presentation is of a firm, raised pearly nodule with central ulceration. Alternation of the normal eyelid structure, such as lid notching or loss of eyelashes, should alert you to the possibility of malignancy.

Andrew McNaught, consultant ophthalmic surgeon
Email: email

Sophia Pathai, senior house officer, West London Ophthalmology Rotation
Email: sophia.pathai@talk21.com


studentBMJ 2003;11:43-86 March ISSN 0966-6494