Prioritising eye referrals in general practice
GP Dr Tonia Myers speaks to Dr Carol Cunningham about danger signs in common eye conditions
lIn the elderly the commonest cause of horizontal diplopia is local microvascular disease due to hypertension or diabetes
lOnly 10 per cent of ophthalmic migraines are associated with headache
lIn a first attack of optic neuritis the optic disc looks healthy
lViral conjunctivitis often runs a two week course with a watery discharge
lNot all retinal detachments present with flashing lights
How should a patient presenting with double vision be properly assessed?
First of all establish whether it is monocular or binocular. Monocular double vision remains when the patient closes the unaffected eye. This is usually caused by a refractive error, corneal surface problem, cataract or macular degeneration.
Binocular double vision goes if the patient closes one eye. This usually implies strabismus, most commonly due to breakdown of a previous squint, but it can indicate more serious pathology such as thyroid disease, myasthenia gravis, inflammatory pseudotumour, cerebral aneurysms or tumours.
It is important to check for proptosis and for restriction of eye movements, in which case thyroid disease is the most likely pathology. Patients with myasthenia gravis may also have restricted eye movements, which are often unequal and intermittent, but they may get a ptosis plus other symptoms of proximal muscle weakness, such as respiratory problems. Associated CNS symptoms are obviously important to ascertain.
What is the importance of the direction of the diplopia?
Diplopia can be vertical, horizontal or something in between. Thyroid eye disease and myasthenia may cause diplopia in either direction, depending on which muscle is involved.
Pure horizontal diplopia on lateral gaze is caused by a lateral rectus palsy, due to a sixth-nerve lesion or to a restricted muscle, as in thyroid disease. In the elderly, the commonest cause is local microvascular disease due to hypertension or diabetes and this would usually warrant a routine referral to an ophthalmologist or a neurologist. However, children must have an MRI scan to exclude a tumour.
To test for horizontal double vision, ask patients to follow a pencil tip without moving their head. With lateral rectus palsy the eye will not be able to look to the affected side and diplopia will occur in this direction of gaze.
Patients who have had a stroke may get variable double vision.
What are the implications of a third-nerve palsy?
This must not be missed as it may be life-threatening, especially if the pupillary reaction is impaired. The third nerve controls the lid, as well as upward, medial and inferior eye movements. There are two parts to the nerve: if the superior part is involved there is restriction of upward eye movement and ptosis, the usual cause being microvascular; the inferior part controls medial and inferior movements and the pupil. Some 95 per cent of compressive lesions such as cerebral aneurysm affect the pupil in a third-nerve palsy.
Remember that ptosis together with a dilated pupil may be caused by an aneurysm and requires urgent referral.
Transient visual disturbances
When patients present with a transient visual disturbance without a headache, how can GPs distinguish atypical migraine from amaurosis fugax?
In a young person if it is transient (less than one hour) it is more likely to be of migrainous vascular aetiology, although you must rule out other pathology, such as a blood flow problem. Does the 'disturbance' float? Is it a scotoma? Does it stay in the same field of vision as the patient moves his/her eyes to right and left, or is there a lag time? Floaters lag because they are floating in the vitreous, but a true scotoma tracks exactly in time with the eye with no lag time.
It is helpful to do a visual field test to identify the pattern of the disturbance and to check if it is actually something that is there all the time, but the patient just notices it once in a while.
The most common stroke-related visual field problem is a hemianopia – with one quadrant or side affected in both visual fields. Bitemporal hemianopia implies a pituitary lesion.
Check the patient's medication because the COC or HRT, for example, will increase risk of migraine. A history of motion sickness is more common in migraineurs. Only 10-20 per cent of ophthalmic migraines are associated with headache, but they may be associated with another aura. A transient visual disturbance associated with scintillating scotoma (zigzag flashes) of light is virtually pathognomonic of migraine.
In older patients check for cardiovascular disease, look for a history of TIAs when amaurosis fugax is more likely. Bruits are not particularly helpful as they do not correlate well with carotid disease. The middle-aged are more difficult and referral for carotid Doppler's will depend on the index of suspicion and complete medical and neurologic examination is indicated.
Sudden loss of vision
What are the causes and are they treatable?
A percentage of patients with age-related macular degeneration with a relatively sudden loss of central vision can be treated with laser. Photodynamic therapy is a relatively new type of laser therapy for subfoveal (central) lesions but it is not widely available.
With central retinal artery occlusion the loss of vision is definitely sudden. It is usually caused by a cholesterol embolism in the arterial tree. This requires very rapid treatment in a specialist centre such as Moorfields, but the visual loss is often permanent.
Treatment is paracentesis – drawing fluid out to reduce pressure. If done within the first few hours, sometimes visual field can come back partially, but we do not often see them in time.
With retinal vein occlusion, people often wake up and notice they have lost vision overnight. Treatment is with prophylactic laser for ischaemic central retinal vein occlusions to prevent secondary glaucoma. Vision does not usually improve.
In cases of non-ischaemic branch vein occlusions where the vision is down because of macular oedema and which does not improve spontaneously after several months, laser treatment can improve vision.
In ischaemic optic neuropathy there is often a classical curtain effect or altitudinal defect where half the visual field – either superior or inferior – goes.
Patients with temporal arteritis may have decreased vision and/or double vision if any extra-ocular muscles are affected. Classically there is temporal artery tenderness and loss of pulse in the temporal artery. There may also be jaw claudication or scalp tenderness. Importantly, the fellow eye can develop ischaemic optic neuropathy in 75 per cent of cases without treatment.
What should make us suspect optic neuritis?
In the first attack it may be difficult to diagnose on examination because the optic disc is almost always a healthy pink and only turns pale later or after multiple bouts. Classically the patient does not see anything and the ophthalmologist cannot see anything either! Visual acuity may be reduced or the quality is different, but the optic nerve looks fine, the cornea is clear, the retina looks fine. Hue discrimination is often reduced on the red hue test in the affected eye.
Vision does not usually fluctuate but normally gets better over several weeks;
there may be pain on eye movement.
Patients may complain that their vision is worse in a hot bath.
What should be done for patients who seem to have acute conjunctivitis with persistent symptoms that don't improve with antibiotic drops? Is it safe to assume they are viral? When should they be referred?
In a painless eye without photophobia where the pupil reacts normally and the cornea is clear, the aetiology is usually viral and it often runs a two-week course, so it is important to maintain your resolve. The discharge tends to be watery and mucoid rather than purulent.
There is often some oedema of the lids, the eye can be very weepy and engorged with fluid (chemotic) – the conjunctiva is swollen as well as injected. There is often a recent history of an upper respiratory tract infection and a pre-auricular node is almost pathognomonic. Viral conjunctivitis is highly contagious and patients must be meticulous with hand-washing and have separate towels and linen.
If symptoms are milder and persistent then chlamydia infection should be considered, especially in younger, sexually active patients – referral is necessary for diagnosis by conjunctival scrapings. Chlamydial conjunctivitis is usually unilateral and treatment is with a single dose of clarithromycin 500mg.
Conjunctivitis is distinguishable from acute iritis, which usually presents with pain and photophobia (also suggestive of a corneal problem) and there is classically a mid-dilated pupil. Visual acuity is usually impaired but can also seem to be down in conjunctivitis because the eye is watery, so wipe away any discharge before you test.
In acute iritis the distribution of redness is usually around the cornea (circumcorneal). In chronic iritis there may be an irregular or a butterfly pupil.
How can GPs distinguish patients with uveitis and episcleritis?
That is usually for the ophthalmologist to discern. In a young person if the redness is limited to a small sector with a painful eye but normal vision and the symptoms tend to recur and relapse, it is probably episcleritis. This is usually idiopathic and not associated with systemic disease. The mainstay of treatment is lubricants. Episcleritis is self-limiting and mild; steroids are usually not indicated except in severe cases.
Episcleritis is not usually worrying unless it becomes bilateral and then may have an underlying cause such as collagen vascular disorders, TB, syphilis, rheumatoid arthritis or herpes zoster. Conversely, scleritis characterised by pain, photophobia and decreased vision has a 50 per cent association with underlying systemic disease as above.
What symptoms suggest that a corneal abrasion may be ocular herpes?
Patients with herpes simplex keratopathy usually have a history of cold sores with a recent trigger such as a period of stress or a holiday in bright sunlight. There is usually a classical branched staining defect with fluorescein and an anaesthetic cornea. If you touch the abrasion with a twirled tip of a cotton wool swab with the patient looking upwards and they don't blink, it is highly suggestive of herpetic lesion.
It is essential to refer if there is no previous history. Treatment is topical aciclovir five times a day. Steroid drops used inappropriately cause worsening of herpes and patients sometimes also accidentally do this by squirting steroid nasal sprays in their eye.
For a simple traumatic corneal abrasion with an appropriate history, treatment is simply chloramphenicol ointment and maybe cycloplegia: for example, cyclopentolate drops twice daily to dilate the pupil, which relieves pain by paralysing the ciliary body.
Should all patients with ophthalmic shingles be urgently referred?
If there are lesions affecting the eye itself and any symptoms, then yes, refer immediately. If the eye is quiet, the vision normal and there are no symptoms (such as photophobia or pain) then it is reasonable to prescribe chloramphenicol drops as prophylaxis and get them seen as soon as possible. Herpes zoster can cause keratopathy, iritis and glaucoma, as well as inflammation of the optic nerve and retina. A lesion on the tip of the nose is associated with ocular involvement.
Do not wait to prescribe aciclovir as it is important to treat as early as possible. There is often not much more for the ophthalmologist to do, unless any of the above sequelae occur.
Floaters and retinal detachment
When are floaters serious? How should they be prioritised?
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Patients over 50 who experience flashes of light (photopsia) and a sudden onset of a floater – often described as a veil – are highly likely to have a posterior vitreous detachment (PVD).
Flashes tend to be in an arc pattern in the temporal periphery or central. In PVD the flashes may decrease in frequency or stop after the floater appears, which implies that the vitreous has detached from the retina and the traction causing the flashing has been alleviated.
PVDs should probably be referred because occasionally a small retinal break occurs
when the vitreous detaches, but there is no great urgency. If the patient notices a red streak or the floaters are red, it implies a haemorrhage, which increases the risk of a retinal break – these patients should be referred urgently.
What are the main warning signs of retinal detachment?
There are three main warning signs: a sudden onset of new floaters in a snowstorm of black or red floaters; a curtain effect with a dense progressive visual field loss coming from any direction; and flashes of light. But, remember, not all retinal detachments present with flashing.
Angle closure glaucoma
Open angle glaucoma is usually routinely picked up by the optician finding a raised intraocular pressure (IOP). How can GPs recognise acute glaucoma?
Acute angle closure glaucoma is caused by a sudden rise in IOP; it is an emergency because it may cause permanent damage to the optic disc. The patient is often quite ill with a severe frontal headache and vomiting, which may distract from the signs of a red eye, hazy cornea and fixed semi-dilated pupil. Most patients have some festering warning symptoms of chronic glaucoma that go unrecognised, before they become acute.
A patient who has frontal headache over one eye on waking in the morning, with blurred vision in a quiet or slightly red eye, could have chronic angle closure glaucoma. When the pupil dilates at night the outflow of aqueous humour is impaired and the pressure builds up. Upon waking, the pupil constricts, the closure is released, the pressure goes down and the vision improves – so the symptoms may be ignored.
Chronic angle closure glaucoma is diagnosed by seeing a shallow or moderate anterior chamber and narrow angles on slit lamp examination. Even with a torch alone the iris may look very bowed. The pupil may be irregular due to synechiae and the optic disc may be cupped. Treatment is with pilocarpine 2 per cent drops until the patient undergoes laser iridectomy. Left untreated, this may evolve into acute angle closure glaucoma.
The same symptoms may occur while driving at night, when the pupil dilates. It is therefore important to ask about timing.
How should GPs assess patients with a big swollen black eye they cannot open?
These patients should probably have an ophthalmic assessment for a retinal haemorrhage, tear or detachment, even without symptoms, as there has been blunt trauma to the eye. Check carefully for crepitus.
Beware of sensitivity to light, a sign of traumatic uveitis, which is very common with these injuries. These patients can be difficult to assess and may require an anaesthetic block in order to check the retina.
Treatment may be needed with steroid drops and cycloplegia. If vision is impaired, a common reason after a direct blow injury is a contusion in the macula (commotio retinae). The vision usually recovers with time.
What pointers can you give GPs to decide whether a patient with eyelid cellulitis requires admission?
It is essential to distinguish orbital cellulitis, which requires intravenous antibiotics, from the less serious pre-septal cellulitis. In pre-septal cellulitis the patient presents with a red, swollen eyelid but a white, non-injected conjunctiva.
If ocular movements are full and pupils react normally, the patient can be safely treated with oral antibiotics in the first instance. Orbital cellulitis is characterised by lid cellulitis, conjunctival injection, headache and fever, with diplopia or an abnormal pupillary reaction being highly suspect and urgent referral is indicated.
Tonia Myers is a GP in Chingford, Essex
Carol Cunningham is consultant ophthalmic surgeon, Moorfields Eye Hospital and Northwick Park Hospital50)>