Life-threatening conditions - Part 2

ACUTE PROPTOSIS
A very short history of forward bulging of the eye always constitutes a medical emergency. The causative conditions are all threatening to the eye, but not all are life-threatening. Acute proptosis may be due to:

 Acute orbital cellulitis
 Orbital haemorrhage
 Caroticocavernous fistula
 Cavernous sinus thrombosis.

Orbital cellulitis
The patient with orbital cellulitis presents with a painful red eye. There is eyelid swelling and redness. The patient may be febrile and when the patient is a child there may be nausea and vomiting. It is important to differentiate pre-septal orbital cellulitis from orbital cellulitis. Each requires urgent referral, but it is orbital cellulitis which is life-threatening. Orbital involvement is indicated by the additional presence of proptosis, chemosis, blurred vision and reduced eye movement. The pupil response may become reduced or absent. The fundus may show papilloedema.
Orbital cellulitis is the name given to a widespread inflammation due to bacterial infection of the orbit. It is classified by the anatomical site of the infection. Pre-septal orbital cellulitis is a superficial infection, sited anterior to the orbital septum and occurs most commonly in young children.
Orbital cellulitis proper involves the soft tissues within the orbit posterior to the orbital septum. This occurs more commonly in older children and in adults.
The infection commonly begins elsewhere in the body and the bacteria may gain access to the orbit from a number of different sites of origin. The organism is commonly a virulent pathogen such as Staphylococcus or Streptococcus. The commonest origin of the infection is in the nasal sinuses and the ethmoid sinus is the most commonly involved. Other local sites from which a bacterial infection may spread to the orbit are a dental abscess and facial skin infections. Conjunctival infection, particularly that involving the lacrimal sac with dacryocystitis, may spread into the orbit.
Lastly, the arrival of the bacteria may be metastatic when the bacteria have been blood-borne from a site elsewhere in the body.
An orbital abscess may develop, occasionally anterior to the orbital septum, but more usually within the orbit. The infection may spread posteriorly into the cavernous sinus causing cavernous sinus thrombosis (see later). The sight may be lost as a result of orbital cellulitis by damage to the optic nerve or by invasion of the eye by the organism causing endophthalmitis (Figure 3).

Orbital haemorrhage
Acute proptosis due to orbital haemorrhage is an acute emergency to the eye but is not generally associated with any life-threatening condition. It is likely to follow trauma and occasionally it may be secondary to a generalised haemorrhagic tendency.
It presents with acute proptosis, which may be painful, with blurred vision. The pupil response and ocular movements are also likely to be impaired. The effect on the vision is due either to optic nerve compression or to retinal artery compression.
The fundus may show collapse of the central retinal artery as in central retinal occlusion. Orbital haemorrhage may result in rapid and permanent loss of vision unless the compression is quickly relieved.

Caroticocavernous fistula
Caroticocavernous fistula (Figure 1) is severely threatening to the eye, but it is not normally associated with any immediate threat to life. The vision is likely to be blurred and the eye may be painful. There is proptosis which may be pulsating, swelling of the lids and chemosis of the conjunctiva and congestion of the eye with dilated conjunctival veins.
The retinal veins are congested and there may be retinal haemorrhages. Secondary glaucoma may also be present. The leaking artery is often audible as a bruit within the skull. The condition usually affects one eye, but both eyes may be affected.
Caroticocavernous fistula is due to a defect in the internal carotid artery where it passes through the cavernous venous sinus at the base of the brain. It may result from a skull fracture or from a pre-existing aneurysm which may cause a painful paralysis of the third, fourth and sixth nerves. The fistula allows leakage of arterial blood under pressure into the low-pressure venous system. The raised pressure in the veins that normally drain from the orbit into the cavernous sinus causes dilatation of the veins of the orbit. The condition is most usually the result of head trauma, but may arise spontaneously from a pre-existing aneurysm.

Cavernous sinus thrombosis
The vision is likely to be blurred and the eye painful. There is eye proptosis without pulsation. There is swelling of the lids and chemosis of the conjunctiva with congestion of the eye. The ocular movements are impaired. The fundus may show papilloedema. The condition usually affects one eye and progresses to affect both eyes unless the patient receives prompt treatment. Cavernous sinus thrombosis is usually of infective origin and is likely to progress to a fatal intracranial infection.
HORNER'S SYNDROME
Horner's syndrome is likely to present with the sudden development of a small pupil on the affected side, which is due to interruption of the sympathetic nerve supply to the iris dilator muscle at any point in the long course of these nerves. Some of the possible causes of Horner's syndrome are imminently life-threatening, particularly the dissecting aneurysm of the internal carotid, which may cause a fatal stroke or loss of vision.
The small pupil may be irregular in shape. The pupil reacts to light and to accommodation/convergence by becoming smaller, but fails to dilate in the dark. There is some degree of ptosis due to loss of tone in Mller's muscle and there may be the appearance of enophthalmos (eye retraction), which is described in older textbooks but is actually false and the apparent enophthalmos is due to the lid posture.
There may be some conjunctival injection due to the loss of sympathetic blood vessel control, but the eye is not painful or inflamed unless there is an additional cause for this. In some cases there is anhydrosis (lack of skin sweating) in the affected facial area.
The sudden onset of Horner's syndrome is most usually due to disorders in the head, neck, or in the chest. These disorders include neoplasms, bony diseases of the spine, fracture of the base of the skull, neck injury and vascular disorders of the common carotid, or of the internal carotid artery, such as aneurysms. The diagnosis and referral of Horner's syndrome is a matter of urgency.
The presence of a dissecting aneurysm may be associated with pain in the head and eye on that side. A dissecting aneurysm of the internal carotid artery may be spontaneous, or may follow trauma to the neck. It is, therefore, important to enquire of a history of injury, which the patient may well have regarded as insignificant and not revealed.
The pupil dilates when phenylephrine drops are applied and this is by an excessive amount when the third-order neurone is affected (between the superior cervical ganglion and the eye), or by a normal amount when the first or second order sympathetic neurones are affected.
Horner's syndrome needs to be differentiated from other conditions presenting with one small pupil which are the Argyll Robertson syndrome and ocular ischaemia. The pupil may be small in the late stages of the Holmes Adie syndrome, but the patient is likely to have presented at the early stage with a dilated pupil.
The Argyll Robertson pupil is a small, irregular pupil that fails to react to light either directly or consensually, but does react to accommodation and convergence. It is more often bilateral than unilateral. The condition was originally described in patients with neurosyphilis, but may occur in diabetes and in multiple sclerosis.

PAPILLOEDEMA
The presence of papilloedema indicates that there is a significant problem affecting the optic nerve and some of the possible causes are life-threatening. The optic disc with papilloedema is pink and prominent due to swelling. The veins are engorged and the disc vessels may be partially obscured. The disc margin is blurred and the disc may be surrounded by flame-shaped haemorrhages and exudates.
The patient presents with reduced visual acuity which may vary from negligible to gross. Colour vision may not be affected. There may be a history of obscurations. Field of vision testing may show a variety of defects. There is likely to be a relative afferent pupillary response deficit. The ocular movements may be affected if there is an orbital cause and if the sixth nerve is affected there may be intracranial hypertension. Pain is associated in optic neuritis and headache with intracerebral causes of papilloedema.
Disc oedema may occur as part of a generalised retinal oedema, in raised intracranial pressure, in raised orbital pressure, or in inflammatory conditions affecting the optic nerve. The term 'papilloedema' is usually reserved for disc oedema due to raised intracranial pressure. A generalised retinal oedema is likely to result from ischaemia with life-threatening causes including severe hypertension, carotid arterial occlusion and temporal arteritis. Raised intracranial pressure can be benign, but the causes include many life-threatening conditions such as intracranial infections and tumours. The inflammatory causes act by causing optic neuritis, which, when anterior, results in disc oedema.

Hypertension
Disc oedema is caused by severe hypertension, sometimes called malignant hypertension, which is life-threatening, particularly with the risk of stroke or of myocardial infarction.
Hypertension is quite common, affecting more than 10 per cent of the older population. Malignant hypertension is rare, but may occur at a young age and may be rapid in onset (Figure 2). The visual acuity is unaffected in moderately-raised blood pressure, but the sight becomes blurred in malignant hypertension. Moderate degrees of hypertension may not show on retinal examination, but life-threatening hypertension produces obvious changes. There is narrowing of the retinal arterioles with increased reflexes, nipping and hump-back bridging may be seen where venules are crossed by arterioles.
In malignant hypertension there is further narrowing of the arterioles which may actually be closed. The vessel walls become irregular and microaneurysms may form. The ischaemia caused by vessel closure may cause retinal infarcts, which show as cotton-wool spots. The retinal vessels leak, producing haemorrhages and hard exudates.
The haemorrhages are characteristically flame-shaped in the nerve fibre layer and dot and blot in the deeper layers of the retina. Hard exudates tend to form in a star shape around the macula, or sometimes in a circinate pattern. Cotton-wool spots are due to ischaemic infarcts of the retina and are always a sign of a severe and probably life-threatening hypertension. Visual acuity becomes affected in hypertension if oedema affects the macula. When optic disc oedema occurs, it indicates that the hypertension has become very severe.

Endophthalmitis
Endophthalmitis is most usually due to infection of the eye following ocular injury or surgery, when it is not life-threatening, but it is occasionally secondary to systemic infection or to orbital cellulitis when the condition is life threatening. Retinal inflammation usually indicates a life-threatening potential (Figure 3).

 Nicholas Phelps Brown is a consultant ophthalmologist based in London's Harley Street