In the first of two articles, Nicholas Phelps Brown describes life-threatening conditions which all eye care practitioners need to be aware of
Patients occasionally present to the optometrist with life-threatening conditions for which incisive action by the optometrist can be life saving.
Incisive action is likely to mean immediate referral to the nearest hospital A&E, rather than the usual referral via the general practitioner. (There are other conditions which are sight threatening, but not life threatening and need equally urgent referral).
There are just a handful of life-threatening symptoms and signs to be aware of. The life-threatening symptoms and signs include the sudden or recent onset of any of the following:
The underlying pathological conditions which account for the life-threatening symptoms and signs include:
Other underlying pathological conditions which account for the possibly life-threatening symptoms and signs, but are not usually life-threatening, include:
HEADACHE
The majority of headaches are harmless and not life-threatening, but headache becomes a significant part of the threat when it is associated with loss of vision, amaurosis fugax, field loss, or with an ocular palsy.
It is, therefore, important to do field of vision testing, ocular motility testing and pupil responses in patients presenting with headache.
The conditions responsible for headache associated with field loss and with ocular palsies are ocular ischaemia, intracranial aneurysms, tumours, cerebral ischaemia, infections (Figure 1) and raised intracranial pressure.
Cerebral aneurysm
The symptoms of cerebral aneurysm depend on whether they are leaking. The peak age for presentation is around the age of 50 years. A non-leaking aneurysm produces effects by compression of nerves and may not cause any pain or headache. Once the aneurysm leaks there is headache, photophobia and neck stiffness together with the effects of further nerve compression. The burst aneurysm produces a subarachnoid haemorrhage which may be fatal.
The ophthalmic symptoms of aneurysms are very variable depending on the site of the aneurysm. An aneurysm compressing the chiasma typically produces bitemporal field loss (Figure 2).
Aneurysms may also cause third, fourth and sixth nerve palsies, and may be responsible for caroticocavernous fistula (Figure 5) and for Horner's syndrome.
Temporal arteritis
Temporal arteritis often presents with headache and with visual symptoms which may be followed rapidly by death due to stroke or by blindness, unless the patient receives urgent treatment. The ocular symptoms include amaurosis fugax with episodes of blurred or obscured vision. An episode may not be short-lived and blindness may result. Diplopia may occur due to ischaemia of the nerves of ocular movement. The ophthalmic examination is usually normal and the fundus of the eye is only seen to be affected very occasionally with signs of arterial occlusion or with papilloedema.
Temporal arteritis is a rare disorder that affects people of 60 and older. The symptoms are variable depending on which arteries are affected.
Headache in the temporal region is common. There may be altered sensation in the scalp with a crawling sensation. Pain on eating is common. The temporal artery may feel thickened and tender to palpation and it may lack a normal pulse. The patient is likely to feel generally unwell and may be febrile. There may be alterations of mood including psychological disturbance. When blindness occurs, it does so early in the course of the disease and it is exceptional for it to occur once corticosteroid treatment has been begun.
Temporal arteritis is one of the auto-immune disorders. The misdirected attack by the body's immune system is on the wall of blood vessels which are invaded by giant cells of the white cell lineage. The blood vessels in the head region are the most usually affected. The swelling in the vessel walls narrows the lumen which reduces blood flow to the part supplied by that artery and total occlusion of the artery may occur with necrosis of the part of the body supplied. When the ophthalmic artery becomes closed the result is blindness. Closure of a cerebral artery causes a stroke which may be fatal.
The diagnosis of temporal arteritis can seldom be fully secure, but since possible blindness and death is such a serious outcome urgent referral is needed on the reasonable suspicion of temporal arteritis.
Cerebral infection
Cerebral infection may take the form of meningitis or of a cerebral abscess. The symptoms depend on the site of the infection.
The presentation is often visual, with reduced visual acuity in a patient with headache who is feeling unwell. There may be a history of a preceding infection such as an inner ear infection. A variety of field-of-vision defects and ocular palsies may occur.
The patient is in urgent need of antibiotic treatment and surgical drainage of an abscess may be needed to preserve life.
REDUCED VISION OR FIELD VISION
Acute reduction in vision or loss of field is always grounds for urgent referral regardless of the presence of any associated symptoms and signs. It may not always be life-threatening, but several of the possible causes do threaten life.
Ask about the patient's health and about associated symptoms such as headache. If there is a sudden reduction in visual acuity also examine the fields, pupil responses and ocular motility.
The life-threatening causes of acute reduction in vision or of loss of field include cerebral aneurysms, cerebral infections, cerebral ischaemia, raised intracranial pressure and severe hypertension. Events within the eye such as retinal vein occlusion (Figure 3) are usually not life-threatening, but retinal artery occlusion (Figure 4) indicates a life-threatening condition when it is associated with temporal arteritis, carotid artery stenosis, or with cardiac arrhythmia. The retina is occasionally the presenting site of life-threatening malignancy such as leukaemia and metastatic tumours and occasionally the presenting site of systemic infections.
Amaurosis fugax
Amaurosis fugax means fleeting loss of vision. It may affect one or both eyes and is usually the result of temporary interruption of blood flow to the retina or optic nerve. In bilateral cases it is likely to be cerebral in origin. It occurs as a result of low perfusion by an artery or as a result of temporary embolic occlusion. However, fleeting loss of vision may also occur in other conditions. for example in optic neuritis when it is traditionally referred to as an obscuration. It may occur in patients who have recovered from optic neuritis in whom exertion causes loss of vision when it is known as Uhtoff's phenomenon. It may be a component of the visual aura of migraine. The causes of amaurosis fugax are also the causes of permanent loss of vision.
Conditions causative of amaurosis fugax
The amaurotic attack is characterised by rapid painless loss of vision followed by a complete recovery in about 20 minutes. Fleeting homonymous field loss may occur in vertebrobasillar ischaemia, affecting the visual cortex and is also a feature of migraine. Incomplete attacks of amaurosis fugax may be described by the patient as episodes of blurred vision.
Headache is an important symptom in association with amaurosis fugax. It may follow the visual disturbance as in migraine, or it may be present more continually, as in ischaemia and in optic neuritis.
The passage of platelet or cholesterol emboli through the small vessels causes amaurosis fugax by temporary interruption of the blood supply.
The emboli arise from the aggregation of platelets in the heart or great vessels. This is usually the result of atherosclerosis of the carotid arteries and in the heart it may be due to arrhythmia. Platelet emboli may cause permanent occlusion (Figure 4). Temporal arteritis is an important ischaemic cause of amaurosis fugax (see above).
The carotid arteries may become narrowed in older persons due to atherosclerosis and a carotid artery may become so severely affected as to be totally occluded. This may result in ocular ischaemia or amaurosis fugax and this is likely to be followed by a stroke. Early referral in this situation can lead to the patient receiving anti-coagulant treatment in time to prevent the stroke.
Ocular ischaemia is an important cause of amaurosis fugax and of persisting loss of vision. (See below).
Migraine is the only benign condition causing temporary loss of vision, although exceptionally permanent loss of vision has been known to occur.
Transient losses of vision called obscurations are characteristic of papilloedema due to raised intracranial pressure. Obscurations last for only a few seconds and are brought on by changes in head posture.
Uhtoff's phenomenon is a transient episode of diminished vision brought on by increased body temperature in an eye that had previously suffered optic neuritis due to demyelinating disease. It is seen in patients affected by multiple sclerosis and typically follows physical exertion.
The examination of the eye in between attacks of amaurosis fugax is usually normal. However, it is likely that the retinal arteries will show arteriosclerotic changes with increased light reflexes described as 'silver wiring'. There may possibly be a gleaming cholesterol plaque (Hollenhorst's plaque) that is residual to a previous platelet embolus. The eye may show signs of ocular ischaemia.
The examination of the eye at the time of an attack may show retinal pallor, empty veins or an irregular distribution of blood in the veins known as 'cattle trucking'. The passage of white material may be seen in the retinal vessels and this is presumed to be the passage of platelet emboli.
Ocular ischaemia
Ocular ischaemia is an important cause of amaurosis fugax and of persisting loss of vision. It occurs as a result of a poor perfusion pressure in the ophthalmic artery producing generalised ischaemia of the eye. Carotid artery stenosis is most commonly the cause and less commonly an arterial aneurysm or a caroticocavernous fistula (Figure 5).
In ocular ischaemia there is often pain in the eye and pain radiating from the eye. The fundus may show attenuation of the arteries and venous dilatation. There may be dot and blot haemorrhages and soft exudates. Cotton-wool spots are due to retinal infarcts and occur in a number of conditions. Cotton-wool spots always indicate a severe problem and the most recent condition to be added to the list is AIDS. In established cases of ocular ischaemia neovascularisation develops with new vessels growing from the disc and onto the iris. The latter causes rubeosis iridis and when found it clearly indicates ischaemia.
The eye condition early in ocular ischaemia may show miosis, ptosis and enophthalmos, which resembles Horner's syndrome. However, there are likely to be many more eye symptoms in ocular ischaemia, including reduced visual acuity, ocular pain, amaurosis fugax and diplopia. Once the eye becomes severely ischaemic then the pupil becomes fixedly dilated.
OCULAR PALSY
The causes of a sudden onset of ocular palsy vary from trivial to be followed by a good recovery to those causes that are life-threatening.
An acute ocular palsy presents with diplopia and with restricted eye movement, but the patient may have difficulty in describing the diplopia and complains of visual confusion. Ptosis and the control of the pupil may also be affected. A painful onset is significant.
The basic mechanisms are ischaemia, compression and inflammation of the nerves or nerve nuclei. The causes include many orbital and intracranial conditions which may affect a nerve of eye movement centrally or peripherally. A defective blood supply is causative in temporal arteritis and in internal carotid obstruction. The condition is relatively common in the diabetic when it is due to microvascular deficiency. Diabetic patients often make a good recovery.
The orbital causes are mostly considered under the heading of 'Proptosis' in Part 2. These include orbital haemorrhage and orbital cellulitis. The intracranial causes include demyelinating disease such as multiple sclerosis, intracranial infections and haemorrhage. An aneurysm may swell and press on a nerve causing a palsy and this may be followed by an intracranial haemorrhage or by a caroticocavernous fistula. Raised intracranial pressure may cause sixth nerve palsy. When the onset of a nerve palsy is painful, the cause to suspect is an aneurysm, haemorrhage, or infection and referral is urgent. A painful onset is also seen in herpes zoster.
The pupil may or may not be dilated in third nerve paralysis depending on whether the parasympathetic fibres are affected. The eye with third nerve palsy is also likely to be affected by ptosis and is turned down and out. When a third nerve palsy is due to compression by intracranial haemorrhage the parasympathetic fibres in the third nerve tend to be affected before the motor fibres because the parasympathetic fibres run on the surface of the nerve. A third nerve palsy without pupil dilatation is typical of a vascular ischaemic cause. The sparing of the pupil function is possible because the parasympathetic fibres accompanying the third nerve run on the surface of the nerve and receive a separate blood supply to that of the core of the nerve.