‘Red eye’ is one of the most common reasons for consulting a GP. Patients often present acutely and may be apprehensive, fearing visual loss. Fortunately, many of the causes are mild and self-limiting, such as bacterial conjunctivitis. However, delay in diagnosis can have a profound impact on vision in more serious cases. Acute glaucoma, for instance, can lead to blindness if untreated.
Figure 53 summarises the features and management of some of the more common and important causes of red eye.
History
Try to avoid making a ‘spot diagnosis’ simply because the patient is presenting with a physical sign. You will make a more precise diagnosis by taking a quick but structured history. The eye is essentially an extension of the brain and the history is as critical here as it is in neurology. Listen to your patients. They bring their own expert perspective to the consultation.
- Can the patient tell you the diagnosis? The child may be prone to recurrent bacterial conjunctivitis. The adult may have the seasonal conjunctivitis of hay fever. Contact lenses may be causing irritation. There could be recurrent herpes simplex keratitis.
A foreign body can cause a corneal abrasion.
Chemical exposure can lead to conjunctivitis or keratitis.
- Are there systemic features? In shingles (herpes zoster) there may be a high temperature and ipsilateral forehead rash and neuralgia. Or there may be a history of a connective tissue disease such as rheumatoid arthritis in a patient presenting with uveitis.
- Is there discomfort (as in the itch of hay fever) or pain?
Pain can be serious, for instance the ‘boring’ orbital pain of acute angle glaucoma (angle closure glaucoma, AAG).
- Are the eyelids crusty or flaky? These are typical features of blepharitis which particularly affects patients with a history of seborrhoeic dermatitis or rosacea.
- Are the eyes unusually sensitive to light? Photophobia is a feature of many eye and CNS conditions, including acute anterior uveitis (iritis) and of course meningitis.
- Do symptoms affect one or both eyes? Bacterial conjunctivitis often affects one eye whereas viral usually affects both.
- Has there been any discharge or are the eyes sticky on waking? A mucopurulent discharge suggests bacterial conjunctivitis.
- Is vision affected?
Loss of acuity is often linked with the more serious causes, although patients with watery eyes sometimes also say they do not see well.
- Is the presentation acute, chronic or recurrent? This is relevant for subconjunctival haemorrhage (acute but can recur), anterior uveitis (can be chronic) and allergic conjunctivitis caused by hay fever (usually recurrent every year).
- How much of the eye is affected? With subconjunctival haemorrhage, only part of the globe is involved. In uveitis there is circumcorneal injection, while acute conjunctivitis affects the whole eye.
Examination
Depending on the history, you may need to include:
- Check the visual acuity (VA) of each eye
- Use an ophthalmoscope to examine each eye ‘front to back’
- Check pupillary reflexes
- Test visual fields by confrontation if you suspect a field defect.
When documenting VA, record the smallest standard word processor font size for near vision and use a Snellen chart for distance vision.
Using the ophthalmosope, first check the red reflex, then rotate the lens wheel to focus down on lids, surrounding skin, conjunctiva, cornea, sclera and iris then compare the pupils and perform fundoscopy. Remember the acronym PERLA: ‘Pupils Equal and Reactive to Light and Accommodation’.
If there is a history of foreign body in the eye or you suspect a corneal abrasion or ulcer (e.g. herpes simplex dendritic ulcer), fluorescein dye will highlight the defect in blue light.
Eye pressure measurement with a tonometer and in-depth examination with a slit lamp microscope are of great value in certain situations, but seldom possible in general practice.
Investigations
An eye swab (for bacterial culture and sensitivity) is the only investigation commonly undertaken in general practice.
Management
In many situations, simple reassurance is all that is necessary (e.g. subconjunctival haemorrhage, mild bacterial and viral conjunctivitis).
Antibiotics (drops and ointment) are often prescribed for conjunctivitis. Arguably, they are over-prescribed but they have a place for some cases of bacterial conjunctivitis, blepharitis (eyelid inflammation and infection) and superficial abrasions.
Ophthalmologists often prescribe topical steroids to reduce inflammation in many types of keratitis, anterior uveitis and scleritis. These must be avoided if an infective cause has not been ruled out. Herpes simplex keratitis, for instance, will get worse.
Some cases of ‘red eye’ are caused by eyelid disorders such as meibomian cyst (chalazion), stye (hordeolum) and blepharitis (see Figure 53). Ectropion typically affects the lower lid and is caused by muscle weakness in old age. The eye appears red as the inside of lower lid (tarsal conjunctiva) is exposed. Entropion is caused by inversion of the lid causing the eyelashes to rub on the conjunctiva and cornea, and it can result in an irritant conjunctivitis or keratitis.
Some ‘Red Eye’ Red Flags
Reduced visual acuity in any patient presenting with ‘red eye’.
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