The acute red eye is a common presentation in the primary care setting. Most cases are benign in nature, with conjunctivitis being the most common aetiology. There are; however, several serious pathologies that clinicians need to be aware of that require urgent recognition and management.

These serious and potentially sight-threatening causes of red eye include:

  • Acute glaucoma
  • Corneal ulcer, contact lens-related red eye and corneal foreign body
  • Anterior uveitis
  • Scleritis
  • Trauma, such as penetrating eye injury or high-velocity foreign body
  • Chemical injuries
  • Neonatal conjunctivitis.


Assessment of the acute red eye

The assessment of a person with red eye involves taking a detailed history and performing a thorough examination.

Important points in the history include:

  • What is the onset and duration of symptoms?
  • How painful is the eye? (Higher pain levels are more likely with microbial keratitis or mechanical abrasion)
  • Are the symptoms unilateral or bilateral?
  • What associated symptoms are present? (visual changes, pain, foreign body sensation, discharge or photophobia),
  • Does the patient use of contact lenses? (Any presentation of red eye in a contact lens user requires urgent referral for possible microbial keratitis
  • Is there any history of trauma or chemical exposure?
  • Does the patient have a history of previous episodes?
  • It is important to inquire about relevant past medical history and medication. (e.g. cold sores and atopy are risk factors for herpes simplex keratopathy)


Examination of the patient should include the following:

  • Administration of topical local anaesthetic if pain scores are high
  • Inspection of the eye (check for discharge and obvious facial trauma)
  • Check for trichiasis, entropion and ectropion (entropion can cause corneal abrasion and ectropion can cause dry eye and exposure keratopathy)
  • Assessment of visual acuity
  • Examine the conjunctiva, including the tarsal surface (if a foreign body is a possibility, the upper lid should be everted to check for a sub-tarsal foreign body)
  • Fluorescein examination (look for yellow-green uptake using blue light on ophthalmoscopy)
  • Assess pupil reactions (check if the person is photophobic, observe pupil size and shape and check direct and consensual pupillary reflexes)
  • Check the person’s blood pressure, if subconjunctival haemorrhage is suspected.


Document the history and findings of eye examinations (including negative findings). This is particularly important when the management of a unilateral red eye is going to take place in primary care.


Conditions requiring urgent same day referral

The following table summarises the typical clinical features of common urgent conditions that require urgent same day referral:

ConditionTypical history featuresTypical examination features
Acute glaucomaUnilateral eye pain
Blurring of vision
Lights surrounded by haloes
Nausea and vomiting
Reduced visual acuity
Tender and hard eye
Ciliary injection
Fixed, mid-dilated pupil
Corneal ulcer (and contact lens-related red eye)Photophobia
Blurred vision
Severe conjunctival injection
Visible discharge
Eyelid swelling
Visible ulceration on fluorescein staining of the cornea
Corneal foreign bodyPrior history of wind blowing into eye
Prior history of use of hammering or grinding tools
Sensation of foreign body
Visible corneal foreign body on examination
Visual acuity and pupil reflexes usually normal
Anterior uveitisPain (worse when contracting ciliary muscles)
Watering of eye
Past history of inflammatory disorders (e.g. ankylosing spondylitis)
Ciliary injection
Constricted or distorted pupil
Visual acuity may be normal or reduced
ScleritisSevere pain
Past history of connective tissue disorders (e.g. rheumatoid arthritis or SLE)
Reduced visual acuity
Abnormal pupil reactions
Scleritis can lead to perforation of the globe
Neonatal conjunctivitisDiagnosed in any infant presenting with conjunctivitis in first 28 days of lifeCorneal ulceration may occur in gonorrhoeal conjunctivitis
Neonatal chlamydial infection can be associated with a systemic infection, such as pneumonia

Further reading:

NICE Clinical Knowledge Summary on the Red Eye


Thank you to the joint editorial team of for this article.