Ophthalmology GPSI Dr Anup Shah on identifying the serious causes
1 As always, the history is crucial.
The important questions are:
• Is there any eye pain?
• Is there any blurring?
• Is there any sensitivity to light (photophobia)?
If the answer to any of these is yes, the cause is likely to be serious. If no to all three, it may not.
2 Don't be scared to examine.
Anyone presenting with a red eye needs to be examined and have visual acuity checked.
First look at the cornea, then instil fluorescein and look again through the blue light. It's often easy to see a foreign body or corneal change.
Look at the conjunctiva: where is the redness? Check the pupils: they should both react easily to light. Look at the lids and lashes: are they in the right place? Are any lashes rubbing on the cornea? Last, evert the lid: is there anything there?
3 Be especially alert with contact lens wearers.
If anyone who wears contact lenses develops a red eye – irrespective of whether there is pain, photophobia or visual blurring – they must be referred to eye casualty immediately. This could be an aggressive bacterial infection resulting in keratitis or a corneal ulcer. Patients who wear contact lenses can have less sensitive corneas and not always feel pain in the early stages of a potentially blinding condition.
4 Check for sensitivity to light.
The main causes of photophobia are corneal lesions and anterior chamber inflammation – commonly seen as iritis. Both need immediate specialist involvement. If your patient has a red eye and sensitivity to light, they need a slit lamp microscope examination, so refer to eye casualty. Also note that patients with recurrent iritis may not have the photophobia they experienced before, so check their history.
5 Conjunctivitis is common.
Conjunctivitis is commonly viral, allergic, chlamydial or bacterial. Usually it is asymmetrical. Viral conjunctivitis is irritating but shouldn't be painful and doesn't cause much visual disturbance. If it causes pain or blurring, worry about the cornea. Allergic conjunctivitis is generally seasonal but can occur with winter allergens and tends to be itchy and less red. Chlamydial conjunctivitis tends to have more redness and discharge but less itch. Evert the lid and take a swab in all 15 to 30-year-olds. It will be positive more times than you may think.
6 Neonatal conjunctivitis is an emergency.
Conjunctivitis occurring five to 19 days after birth, causing mucopurulent discharge and conjunctival redness, is a medical emergency and a notifiable disease. The most common pathogen is chlamydia, with which there can be an associated systemic infection that can result in otitis, rhinitis and pneumonitis. Gonorrhoea is another common cause. Due to the risk of serious infection, conjunctival and corneal scarring and blindness, this must be treated immediately.
7 Is it angle closure glaucoma?
Angle closure glaucoma occurs when the normal drainage angle of the aqueous humour closes up. The eye still produces aqueous humour and intraocular pressure rises. This occurs when the anterior chamber is shallow and is compounded as the lens thickens and grows forwards. A high pressure in the eye causes significant pain and makes the pupil less reactive. This usually occurs in people over the age of 50 with thickened lens.
For the same reason, acute angle closure glaucoma is very rare in those who have had cataract surgery and the thickened lens removed.
8 Could it be shingles?
Some 15% of all shingles cases affect the first division of the trigeminal nerve – herpes zoster ophthalmicus. Occasionally the eye can become involved if the disease involves the maxillary nerve. If the tip of the nose is affected, there is a significant risk that the eye will be, because the external nasal nerve that supplies the tip of the nose is the terminal branch of the nasociliary nerve that supplies the eye. This is Hutchinson's sign. Shingles can cause conjunctivitis, keratitis, iritis, raised intraocular pressure and can also affect the posterior segment. If the patient has shingles and the eye is red and you are concerned, they need ophthalmological assessment.
9 Check what they're putting in their eyes.
OTC remedies vary from lubricants, antibacterials and ‘soothers'. The preservatives in these and in some prescribed drops can cause a red, irritated eye. Continued use can make things worse. If a patient is using an OTC product, ask them to stop and let things settle. If their problems have arisen with a prescribed drop, it is worth trying a preservative-free formulation.
10 Don't be scared.
Most patients in primary care with a red eye tend to have something self-limiting and innocuous. If the answer to the three questions is no, think about sub-conjunctival haemorrhage, episcleritis, conjunctivitis or a small conjunctival lesion. Don't be afraid to look or to stain with fluorescein. But as always, if the symptoms don't resolve, or cause you or your patient to worry – don't be afraid to refer.
Dr Anup Shah is a GPSI in ophthalmology in London
Competing interests None declared
Dr Anup Shah is also a lecturer for Primary Care Ophthalmology, which offers courses in ophthalmology for the 10-minute consultation. The next course is on 11 October at the RCGP. More details at www.primarycareophthalmology.co.uk
Ten Top TIps on red eye
