Ophthalmology referral dilemmas

Consultant ophthalmologist Mr Hunter Maclean describes nine presentations and how best to refer them

Eye complaints can be complex, and understanding the possible causes can help GPs in deciding whether to refer to an ophthalmology department or if another specialist department would be more appropriate.

Double vision

Ophthalmologists are well trained here and are an ideal referral destination in most cases.

First, is the double vision uniocular or binocular? If it is uniocular, cataracts are probably the cause.

Secondly, is the double vision a cranial nerve palsy or is it a restrictive muscle problem such as a fracture of the floor of the orbit? Or is it a swollen muscle as in thyroid eye disease? Orthoptists in ophthalmology departments will plot the strength of each eye muscle which can often be used to make a diagnosis.

The sixth and third nerve palsy are the most common in clinical practice and can be quite subtle, with little to see on clinical examination. Most obvious cases will be seen as a convergent squint when looking straight ahead (sixth nerve palsy) and a divergent squint in a third nerve palsy. The cause is usually diabetes or hypertension with the condition settling back to normal in a few months. If an unusual feature – such as proptosis – is discovered, scanning and referral can be organised.

One scenario that is rare but worth looking out for is a painful third nerve palsy. This can occur in patients aged 20 to 80 with a mean of around 50. On examination there is a fixed dilated pupil (as opposed to the usual third nerve palsy where the pupil is unaffected).

The cause is likely to be an aneurysm in the Circle of Willis and the patient is in danger of a life-threatening subarachnoid haemorrhage. These patients need to be referred quickly to neurosurgery.

Transient visual loss

This is a common clinical scenario encountered in ophthalmology and there are two main diagnoses to tease out – amaurosis fugax and ocular migraine. Both are neurological in cause, but are nevertheless routinely dealt with in ophthalmology departments.

While the description of transient visual loss incorporates both conditions there are clear differences in the history.

In amaurosis fugax the history is of a black curtain coming down over the vision that lasts about three minutes and then recovers. During the three minutes – and the timing is remarkably consistent – there is complete darkness.

In ocular migraine there is a visual disturbance of spiralling or zigzagging lights (this often has many varied descriptions) that gradually enlarges, culminating in loss of central vision and eventual recovery. The whole process takes 20-30 minutes and the timing is once again remarkably consistent. There is often no headache.

Amaurosis fugax is a form of TIA and is a potential precursor to stroke. Carotid Doppler examination is helpful to discover any carotid artery disease that would be amenable to carotid endarterectomy. But as part of the work-up an ophthalmology department would also take a history for giant cell arteritis and test for a raised ESR and CRP. Giant cell arteritis causing transient visual loss is an important diagnosis to make as the treatment (steroids) is different and there is the potential for blindness if the condition is not recognised and properly treated.

Ptosis

By far and away the most common causes of ptosis are age-related stretching of the levator aponeurosis in adults and congenital factors in children. These are corrected by surgery and are the domain of the ophthalmologist – generally those subspecialising in oculoplastic surgery.

But some forms of ptosis are neurological, for instance myasthenia gravis. If clinical suspicion of myasthenia gravis is high a direct neurology referral would seem sensible. But note that all forms of ptosis have an element of fatigue.

Facial palsy

Acutely, cases of facial palsy are best referred to ENT, principally for treatment of more sinister causes. But ophthalmology referral is required fairly promptly if there is concern about corneal exposure.

A sore and red eye are the danger signs of a struggling cornea. The cornea has three main defence mechanisms – corneal sensation, watering and eyelid closure. If two of the three are intact the cornea will usually be all right.

Eyelid closure is usually the problem with facial palsy but as long as the Bell's phenomenon (rolling of the eye upwards during closure) is brisk the cornea is unlikely to come to harm. Supplementary artificial tears are beneficial.

In the long term, referral to ophthalmology is helpful if the palsy has not recovered and will not. In these cases, surgery to correct the usual ectropion and an upper-lid weight to help with closure of the eye may be helpful.

Blepharospasm/hemifacial spasm

These two debilitating conditions, particularly hemifacial spasm, can be effectively treated with botulinum toxin injections. The injections are required every three to four months as the toxin degrades with time. Which specialism offers this service is likely to vary around the country but is usually ophthalmology units.

Watering eye

The causes of a watering eye are diverse and range from lid laxity to blockage of the nasolacrimal duct. These are best investigated by the oculoplastic specialist in the ophthalmology department.

Blockage of the nasolacrimal system can be treated by engineering a new passage into the nose (dacryocystorhinostomy), providing an alternative route for the drainage of tears. This operation can be done externally or endonasally. In some units the endonasal route would be in collaboration with an ENT surgeon.

Optic neuritis

The patient would generally present with unilateral loss of central vision and the cause of this would be best invesigated in the ophthalmology department.

A single episode of optic neuritis usually passes off with no problem but recurrent attacks imply a possible diagnosis of multiple sclerosis and at that point a neurology referral is appropriate.

Iritis

This commonly presents as a painful red eye that gets worse each day it is not treated. There is no sticky discharge, which distinguishes it from conjunctivitis – with which it is commonly confused.

A slit lamp examination in the eye department is required for the diagnosis to be confirmed. Some 99% of cases are idiopathic and no further investigations are required. If there are any unusual features suggesting systemic involvement, the ophthalmologist will consult the appropriate physician depending on the systemic features – for instance, a respiratory physician in a case of sarcoid-induced uveitis.

Dermatological conditions near the eye

The eyelid and eye area are very common sites for basal cell carcinomas.

Surgery to remove these carcinomas and other dermatological conditions requires precise understanding of the local anatomy and specialised surgical techniques in order to prevent complications such as postoperative ectropion and watering.

Any skin condition requiring excision appearing in an area roughly equivalent to that covered by a scuba diver's mask is best examined by an oculoplastic specialist in the eye department. Lesions elsewhere can be referred to dermatology. Mohs surgery is a technique that improves the likelihood of complete tumour removal while also preserving as much vital tissue as possible. Many eye departments will collaborate with a Mohs specialist in the dermatology department for the complete removal of basal cell carcinomas. Reconstruction of the skin defect is then carried out by an ophthalmologist specialising in oculoplastics.

Mr Hunter Maclean is a general ophthalmic surgeon at the Queen Alexandra Hospital, Portsmouth, specialising in oculoplastics and lacrimal surgery. He also practises from Spire Hospital, Havant and Optegra, Solent Eye Care Centre