First aid must be started as quickly as possible: firm pressure to the eye through the eye lid with the edge of a fisted hand, rhythmically, for about 10 seconds followed by a sudden release and a pause of 10 seconds (may also be instructed to the patient over the telephone; make sure the patient has not recently undergone eye surgery or sustained an eye injury). Ocular massage may be continued (for at least 15 minutes) until other treatment is initiated.
Aspirin 250 mg may be given as first aid.
The patient must be sent immediately to an ophthalmic emergency department. Irreversible retinal damage starts to occur 1½ hours after the occlusion.
Aetiological investigations are started as soon as possible after the detection of the occlusion, as is done with all other disturbances of the cerebral circulation as well.
Aetiology
Central retinal artery occlusion (CRAO) may be of carotid artery origin or it can be caused by an embolus originating from the heart.
Past medical history includes episodes of TIA in about 10% of patients.
Ocular TIA (amaurosis fugax) is an acute unilateral vision loss that lasts from a few minutes (3-5 minutes) to half an hour.
A transient circulatory disturbance affecting the vertebrobasilar area may be associated with total or partial bilateral vision loss with a duration of < 1 minute and with other concurrent symptoms such as slurred speech and vertigo.
The typical patient is an elderly person with cardiovascular diseases, more rarely a younger patient with e.g. cardiac arrhythmia or a valvular heart defect.
Temporal arteritis must always be excluded (the sight may be saved in the fellow eye with glucocorticoids!).
The dominant symptom in temporal arteritis is intense headache. The arteritis usually causes narrowing of the visual field before vision loss, and the vision loss is not abrupt Giant Cell (Temporal) Arteritis.
The condition may be associated in many ways with the use of illegal drugs (e.g. talc emboli, cocaine-induced vasospasm).
Symptoms
Sudden, painless unilateral loss of vision or a visual field
Findings
Vision is usually reduced to the level of counting fingers or only light perception in about 20% of patients.
Central vision may be saved by a cilioretinal artery (occurs in about 10% of the population), which supplies the macula.
The pupil is semi-dilated and reacts poorly to light.
The fundus appears normal in the beginning, but becomes milky white within one hour. A cherry red spot becomes visible in the macula (absent if the occlusion is in the ophthalmic artery).
In branch retinal artery occlusion (BRAO; picture 1), changes are only present peripherally to the occlusion with a corresponding partial visual field deficit.
The arteries are narrow with segmentation of the blood column; sometimes shiny cholesterol crystals (Hollenhorst plaques), usually deriving from cholesterol plaques in the carotid arteries or cardiac valves, or light-coloured calcific emboli may be visible.
During the subsequent weeks the oedema subsides and both the retina and optic nerve will atrophy. The arteries will remain narrow.
Emergency first aid
First aid must be started as quickly as possible!
The patient may start ocular massage at home by repeatedly applying firm pressure to the eye with the edge of a fisted hand for about 10 seconds followed by a sudden release which may make the embolic clot to dislodge and move forward within the vessel. Pressing of the eye increases the intraocular pressure which leads to dilatation of the artery. The intraocular pressure drops when the pressure is released which also improves blood flow. This may return circulation at least to a part of the central retina, i.e. CRAO becomes BRAO.
The patient should continue with the digital optic massage until arrival at a medical facility.
If the order to start ocular massage is given over the telephone, it must be checked that no surgery has recently been carried out to the affected eye (e.g. cataract surgery) and that it has not sustained an injury.
At the first aid centre, aspirin 250 mg may be given by mouth after which the patient must be sent immediately to an ophthalmic emergency department.
Anterior chamber paracentesis can be carried out at an ophthalmic emergency department in order to lower the intraocular pressure.
These measures should be attempted if less than 3-8 hours have elapsed from vision loss.
It has been shown experimentally that irreversible retinal damage starts to occur as early as 100 minutes after the occlusion.
Local ophthalmic artery thrombolysis has been associated with severe adverse effects.
Aetiological investigations
TIAs, as well as CRAO and BRAO are all warning signs of a stroke! A general recommendation about immediate investigations within a neurological unit applies to these conditions.
Consult an on-call neurologist. Investigations to reveal the aetiology of the occlusion and planning of secondary prevention should be started the next day after the diagnosis at the latest (see Transient Ischaemic Attack (TIA)).
Investigations
Laboratory tests:ESR, CRP, basic blood count with platelet count, plasma sodium, potassium, lipids, glucose (glucose tolerance test later if needed), alanine aminotransferase, gamma-glutamyl transferase, creatinine, INR (in patients on anticoagulation therapy), APTT
Blood pressure monitoring
Carotid ultrasonography (to determine the degree of possible carotid stenosis)
Head CT or MRI
Chest x-ray (heart failure)
ECG (e.g. atrial fibrillation, myocardial infarction), echocardiography as needed
If considered necessary, clotting factor studies are performed on younger patients (less than 50 years of age) if the aetiological investigations do not reveal other factors predisposing to the occlusion (vasculitis, use of intravenous drugs), or if the patient has occlusions both on the arterial and venous side.
When a Hollenhorst crystal is found in an asymptomatic person, the investigations to find out the aetiology and the planning and implementation of secondary prevention can be carried out within primary or occupational health care. If a significant carotid artery stenosis is found, the patient is referred to a vascular surgeon.