Overview

Red eye is a common presentation in primary care and in the emergency department. Most cases will be due to relatively trivial problems.¹ The most common cause of red eye presenting in a primary care setting is conjunctivitis.² A small proportion of red eye cases are serious and need urgent treatment. The challenge lies in discerning one from the other. This record aims to guide you to the likely diagnosis. More detailed information on the conditions and their management can be found in the linked articles.

There are a number of ways of 'classifying' a red eye but perhaps the most practical is whether there is associated pain or not. Intrinsically associated with this is the visual acuity (VA) which must be measured for both eyes of all patients. Where this is impaired, it is absolutely vital to rule out serious pathology.

Assessment of the red eye

History

The basic structure is no different than for other systems but take particular note of the following:

• History of presenting complaint - the time and speed of onset, ocular associations (e.g. photophobia, blurry vision, discharge, etc.), systemic associations (e.g. headaches, nausea, a rash on the forehead) and what the fellow eye is up to - a surprising number of patients fail to tell you about symptoms there. Specifically enquire about trauma, however minor it appears to have been.
• Past ocular history - similar episodes, other episodes, surgery, 'lazy eye' (which would guide you as to whether the recorded visual acuity (VA) is worrying or not). Do they wear, or have they worn, contact lenses and ask about their care in use of contact lenses, e.g. do they forget to clean them? Do they forget to take daily disposable lenses out at night?
• Social history - has this nursery school teacher been in contact with a young child with a red/sticky eye? Will this elderly patient manage intensive eye treatment on their own? Extra support may need to be thought about to prevent admission.

Examination

It is essential to record the VA and carry out a careful anatomical examination (start anteriorly and work your way backwards). Pupils and their reactions should also be checked (look for the distorted or small pupil of acute anterior uveitis or the mid dilated fixed pupil of acute angle-closure glaucoma). Go to the separate article Examination of the Eye for details on examination techniques.

If no ocular causes of a red eye emerge, consider potential systemic causes that would prompt a review of the patient's past medical history ± a full physical examination. Scleritis (and, much less commonly, episcleritis) is frequently associated with connective tissue diseases - particularly rheumatoid arthritis, gout, syphilis and, less commonly, tuberculosis, sarcoidosis and hypertension.

The acute painful red eye³

The acute non-painful red eye³

The case of scleritis - not always red

This condition refers to an inflammation of the full thickness of the sclera. In anterior scleritis, there will be diffuse deep injection but in some types (e.g. where there is scleral necrosis) and in posterior scleritis, there may be minimal injection and redness. The key symptom is a gradual onset of severe and boring eye pain which may radiate to the forehead, brow or jaw. Over time (days or weeks), there will be a progressive onset of photophobia and vision will become gradually impaired. Suspect this in the older patient (particularly from the sixth decade onwards) with systemic conditions such as connective tissue disease, gout and previous herpes zoster ophthalmicus. These patients need referring within 24-48 hours for treatment under ophthalmological supervision.

For more detail on scleritis, see separate article Scleritis and Episcleritis.

The case of endophthalmitis - not always painful

This is a rare but potentially devastating condition which can occur postoperatively (within a few days or delayed a month or more post-surgery), post-trauma, in an acutely septicaemic patient, an immunocompromised patient or in intravenous drug abusers. The patient presents with a red eye, decreasing VAs and pain. Although the latter tends to be the norm, it is not invariable so, if you suspect endophthalmitis, do not be reassured by the presence of minimal pain. There will be a hypopyon in the anterior chamber as well as a severe anterior chamber reaction (this will be hazy with fibrin and inflammatory cells) and there may be associated conjunctival chemosis and eyelid oedema. These patients need to be referred urgently (same day) for intravitreal and systemic antibiotics.

See separate article Endophthalmitis for more detail.

The non-acute red eye^1,4

Adnexial causes

• Blepharitis
• Trichiasis/distichiasis
• Floppy eyelid syndrome
• Lagophthalmos
• Dacryocystitis
• Canaliculitis
• Acne rosacea

Conjunctival causes

• Medication toxicity - see separate article Eye Drugs - Prescribing and Administering.
• Injected pinguecula - a pingueculum is a common, innocuous lesion seen as a cluster of yellow-white deposits (usually in a triangular formation with the base adjacent to the cornea), arranged temporally or nasally to the cornea. If it becomes inflamed (pingueculitis), it becomes red and may be slightly elevated. Depending on the symptoms (mild-to-marked discomfort), the patient may benefit from a short course of weak steroids.
• Other causes include Stevens-Johnson syndrome, cicatricial pemphigoid and conjunctival neoplasia (rare).

Corneal causes

It is unusual for a corneal condition to present as a chronic red eye problem. Presentation of long-standing conditions tend to be acute exacerbations of the long-term problem with some or all of the usual symptoms relating to corneal problems (pain, photophobia, may be reduced visual acuity (VA)). Some examples include the presence of a pterygium which has become inflamed, recurrent corneal erosion syndrome and cases of recurrent keratitis (such as marginal keratitis or herpes simplex infection). Patients are often familiar with their condition and its management.

Other causes

• Dry eye syndrome
• Carotid-cavernous sinus fistula
• Cluster headaches

Management

• There is a reduced visual acuity (VA).
• There is moderate-to-severe pain.
• There is photophobia or there are coloured haloes around a point of light.
• There is marked injection (redness) of the eye - particularly unilateral or a ciliary flush.
• There is corneal opacification.
• There is proptosis.
• There is an abnormally reacting pupil in the problem eye.
• A contact lens has recently been worn in the affected eye.
• You suspect a penetrating injury.
• You suspect neonatal conjunctivitis.

Otherwise, refer to relevant articles through the links above for management of specific conditions.

Document references

1. Farina GA et al; The Red Eye, Medscape, Jul 2009
2. Cronau H, Kankanala RR, Mauger T; Diagnosis and Management of Red Eye in Primary Care, American Family Physician. 2010 Jan 15;81(2):137-144
3. Chua CN; Eye casualty: common ocular emergencies and referrals
4. Kunimoto DY, Kanitkar KD, Makar MS; The Wills Eye Manual (4th ed.) 2004. Lippincott, Williams and Wilkins
5. Red eye, Clinical Knowledge Summaries (2008)

Acknowledgements