Sudden vision loss in quiet eye
Dr Melanie Wynne-Jones advises on a dilemma
Dr Melanie Wynne-Jones advises on a dilemma
Joan Smith is 62 and says that yesterday the vision in her left eye disappeared over half a minute, as if a blind had been drawn across it. After 10 minutes or so the vision slowly but completely returned. She didn't call anyone because there wasn't any pain and it resolved, but she thought it best to check it out.
What are the causes of sudden vision loss in a 'quiet' eye?
If the eye is not inflamed, the history, and examination of the visual acuity, visual fields and fundus should help to identify the cause; many will need prompt referral. The differential diagnosis includes:
- arterial pathology amaurosis fugax, central retinal artery occlusion, arteriosclerosis, temporal arteritis
- auto-immune and other types of arteritis, intracranial arteriovenous malformation, emboli and thrombocythaemia
- retinal vein thrombosis (usually less dramatic unless macula affected
- retinal detachment
- vitreous haemorrhag
- disciform macular degeneration
- retrobulbar neuritis (usually painful)
- migraine (usually a spreading scotoma and/or scintillae affecting both eyes)
- papilloedema including hypertension
- intraorbital tumour
- patient suddenly noticing longstanding visual field defect.
On examination Mrs Smith's eye seems normal. What should you do now?
The story suggests amaurosis fugax. This is a symptom, not a diagnosis, and should be regarded as a TIA affecting the eye, although it tends to last minutes rather than hours. The management is therefore that of a TIA cardiovascular assessment and risk modification where possible.
The retinal artery is supplied by the internal carotid artery, and amaurosis fugax is frequently due to emboli from endothelial plaques. The heart is another source of emboli. You need to check for:
- cardiac arrhythmias examination and ECG
- signs of heart failure
- signs of hypertension blood pressure, urinary blood/protein
- carotid or other arterial bruits (although a bruit is not diagnostic)
- diabetes blood sugar·hyperlipidaemia fasting lipid
- thrombocythaemia full blood count
- liver function (statin may be required)
- temporal arteritis tender artery with absent pulsation, check ESR and C-reactive protein.
Is further investigation and treatment needed?
Mrs Smith needs prompt referral for a duplex scan of her carotid arteries, as the next event may be a full-blown stroke. This is probably best achieved by referral to the local TIA clinic. Her symptoms and signs may also suggest she needs an echocardiogram, a CT scan of the brain or anticoagulation.The duplex scan will measure the severity of carotid artery stenosis mild (<50 per cent), moderate (50-69 per cent) or severe (70 per cent plus) to determine whether carotid endarterectomy to remove diseased plaque or (occasionally) replacement of a short section of the artery is indicated.
Carotid endarterectomy for >70 per cent blockage halves the risk of further stroke in the next five to eight years; for moderate blockage the risk reduces by about a third. But the procedure carries a risk of stroke or death of around 7 per cent and 1 per cent in the first month.
The results are better after full stroke than TIA, within two weeks of the stroke, and in men and younger people.
What lifestyle advice and treatment should you give Mrs Smith?
Standard advice for lowering her cardiovascular risk should cover:
- not smoking offer help if needed
- drinking within safe limits heavy drinking increases stroke risk
- diet low fat, low salt, more than five portions of fruit and vegetables daily
- blood pressure control using medication if necessary (target <140/85mmHg, 130/80mmHg if diabetic); thiazide diuretics and/or ACE inhibitors are preferred
- cholesterol below Joint British Societies' target using medication if necessary (total cholesterol <4mmol/l, LDL < 2mmol/l, HDL >1mmol/l)
- management of glucose intolerance/diabetes
- aspirin 75mg daily if not allergic or intolerant, or clopidogrel 75mg or dipyramidole 200mg bd
- pneumococcal immunisation and annual flu jab
Mrs Smith should be added to the practice's stroke register using Read code F4236. Many of these clinical targets will automatically be audited for QOF points.
Can Mrs Smith continue driving?
As this is a TIA she should not drive for a month, but need not notify the DVLA unless she has been left with a permanent neurological deficit, or has a further TIA or stroke.
She should notify motor and travel insurers as they may claim she has withheld material information in the event of a future claim, even for unrelated conditions. Vocational and LVG drivers are usually not allowed to resume driving for 12 months after a TIA.