Red Eye

Red eye is a common presentation in primary care and in the emergency department. Most cases will be due to relatively trivial problems.¹ A small proportion of cases need urgent treatment. The challenge lies in discerning one from the other. This article aims to guide you to the likely diagnosis. More detailed information on the conditions and their management can be found in our dedicated 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 which must be measured for both eyes of all patients. Where this is impaired, it is absolutely vital to rule out serious pathology.

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, 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 is worrying or not). Do they or have they worn contact lenses and ask about their level of hygiene (do they forget to clean them? Forget to take daily disposables 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 visual acuity (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 our record on 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 case of scleritis - not always red

This condition refers to an inflammation of the full thickness of the sclera and usually (although not invariably) presents with a red eye. Its presentation is insidious, however, with the key symptom being 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.

See our record on Scleritis for more detail.

The case of endophthalmitis - not always painful

This is a rare but potentially devastating condition which can occur post-operatively (within a few days or delayed a month or more post surgery), post trauma, in an acutely septicaemic patient, immunocompromised patient or in intravenous drug abusers. The patient presents with a red eye, decreasing VAs and pain. Although the latter is very common, 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 urgently referred (same day) for intravitreal and systemic antibiotics.

See record on Endophthalmitis for more detail.

Adnexial causes

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

Conjunctival causes

• Medication toxicity - see article on Conjunctivitis.
• 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 with some or all of the usual symptoms relating to corneal problems (pain, photophobia, may be reduced VA) but recurrent. 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

• There is moderate to severe pain
• There is marked injection (redness) of the eye - particularly unilateral
• There is a reduced VA
• A contact lens has recently been worn in the affected eye
• You suspect a penetrating injury
• You suspect neonatal conjunctivitis

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