The Red Eye
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Most acute ophthalmological presentations can be divided into three main categories:

In this article, we consider the first type of presentation.

There are many causes of a red eye. Below we have outlined the commonest and most important causes.
Causes of a red eye:
  1. Conjunctivitis
  2. Corneal abrasions and ulcers
  3. Acute Iritis aka Anterior Uveitis
  4. Scleritis
  5. Acute Glaucoma
  6. Subconjunctival haemorrhage
  7. Foreign Body
  8. Trauma
  9. Blepharitis
  10. Chalazion


  • Onset and duration
  • Painful or not painful?
  • Unilateral or bilateral?
  • Distribution of the redness – is it diffuse or localised?
    • Diffuse suggests a conjunctivitis, episcleritis or scleritis
    • Localised may suggests a foreign body, or ulceration
  • Contact lens wearer?
  • History of feign body?
  • Any discharge?
  • Any photophobia?
  • History of FHx of autoimmune disease
    • Suggests scleritis or iritis
  • Rash – particularly on the tip of the nose – suggests ophthalmic shingles
  • Visual acuity
    • Improve by pinhole suggests a conjunctivitis
  • Systemic symptoms – headache, vomiting, nausea
    • Suggest acute angle closure glaucoma
  • Slit lamp examination
    • Cloudy cornea?
      • Suggests glaucoma – especially if loss of detail of the iris
    • FB in anterior chamber?
    • Pupillary response and shape
      • Irregular, non-reactive pupil suggests iritis
      • Fixed, mid-dilated but regular shaped pupil suggests glaucoma
    • Evidence of abrasion or foreign body – remember to evert the eye-lids!
    • Fluorescein staining – any evidence of abrasion, ulceration or other uptake?
    • Normal red reflexes?
  • Palpate the eyeballs
    • Firm and tender suggests glaucoma
  • Previous cataract surgery?
    • If yes – extremely unlikely to be glaucoma


  • Gritty irritation/itchiness, watery/purulent discharge, diffuse injection
  • Intensity of injection around the periphery suggests conjunctival inflammation whereas injection around the cornea suggests corneal or intra-ocular inflammation.
  • History of contact with other with conjunctivitis – especially if young children at home!
  • Often bilateral
  • Infective causes:
    • Bacteria – more purulent discharge where eyelids may stick together
    • Viruses – adenovirus is very infectious, small lymphoid aggregates appear as follicles on conjunctiva, pre-auricular lymph node enlargement
    • Chlamydia – young adults or newborns (opthalmia neonatorium is caused by bacteria in the birth canal and must be treated immediately to preserve eyesight)
    • Infective causes typically accompanied by a purulent discharge (but not always)
    • Bacterial conjunctivitis may have more copious amounts of discharge, and viral conjunctivitis tends to have a watery as opposed to bacterial discharge
    • Most cases are viral – usually adenovirus. Consider herpes zoster virus and herpes simplex virus
  • Allergy
    • Very itchy and often watery
  • Vision is normal or very mildly reduced
    • Acuity will always improve with pinhole
  • Treatment depends on the cause: allergic conjunctivitis may respond to antihistamines or self resolve when the allergen is removed, antibiotics clear bacterial conjunctivitis, and viral conjunctivitis will disappear on its own.
    • Many bacterial cases will not require antibiotics
    • Advise patients to wash the eye frequently with either cool boiled water or saline, using cotton wool balls to wipe the eye once before disposing. I advise patients to do this whenever any discharge is present – and to do 5 wipes – with 5 individual cotton wool balls. This can be a lot of wiping!
    • Advised about hygiene measures to reduce the risk of transmission – frequent hand washing at home, avoid sharing of towels and pillows, consider disinfecting surfaces around the house
  • Patients with allergic conjunctivitis may also benefit from lubricating eye drops
  • If marked decrease in visual acuity (<6/9 with pinhole) or photophobia – consider ophthalmology assessment within 24 hours (could represent scleritis or iritis)

Corneal Abrasion

  • This occurs when the surface epithelium is sloughed off – usually due to trauma
  • Pain, foreign body sensation, tearing, red eye
  • Variable reduction in vision
  • Stains with fluorescein
  • Treatment: Analgesia (paracetamol or ibuprofen), Prevention of secondary infection with tetanus prophylaxis and a topical antibiotic for 7 days (chloramphenicol or fusidic acid)
  • Exclude a foreign body which may be trapped under the inside of the upper eyelid. (Invert the upper eyelid over a cotton bud or orange stick.)
Corneal Abrasion
Corneal Abrasion – Image from Wikipedia

Corneal Ulceration

  • Bacterial: Chlamydia, Pseudomonas
  • Viral: Herpes Simplex virus (causes a dendritic ulcer), Herpes Zoster virus
  • Fungal: candida, aspergillus
  • Protozoan: Acanthamoeba in contact lens wearer
Mechanical or trauma. Check for foreign bodies.
Chemical:Alkali injuries are worse than acid – seconds count
Ulceration with keratitis (inflammation of the cornea) is known as ulcerative keratitis and must be treated as an emergency to prevent permanent scarring or visual loss.

Anterior uveitis (iritis)

Inflammation of the anterior uvea, comprising the coloured iris and ciliary body.

Photophobia, circumcorneal redness (due to ciliary congestion), acute pain, lacrimation, decreased vision (due to precipitates in the aqueous), small pupil (due to iris spasms and adhesions)
Most commonly idiopathic.

The pain is often significant and feels like a “deep burning pain” in the eye.
Associated with systemic diseases:

Positive Talbot’s test: pain increases as the eyes converge and pupils constrict (ask the patient to watch their finger approach their nose)
May be complicated by cataract or glaucoma
Often recurs in the same eye
Anterior Uveitis - Hypopyon
The exudate in the cornea seen in anterior uveitis – known as hypopyon. Image from wikipedia
The pupil is often smaller than the unaffected side, and may be irregular due to adhesions.
Initial management
  • Refer urgently to ophthalmology – call you local on-call ophthalmology service
  • Steroid eyedrops are often recommended but you MUST ensure you have the diagnosis right, because they can precipitate or worsen glaucoma, cause cataracts and lead to infections such as a keratitis – and all of these potential complications are sight threatening
  • Do NOT start steroid eye drops without the consent and advice of an ophthalmologist


  • Superficial irritation and inflammation of the episclera, a thin layer of tissue covering the sclera of the eye.
  • Idiopathic, collagen vascular disorder (Rheumatoid Arthritis). It occurs without an infection.
  • Asymptomatic, mild pain
  • Self-limiting without treatment within 1-2 weeks or topical corticosteroid eye drops may relieve the symptoms faster. Rarely, scleritis may develop.


Inflammation of the sclera causes a severely deep boring pain that wakes the patient at night, lacrimation, photophobia

  • Idiopathic
  • Collagen vascular disease (Rheumatoid Arthritis, Ankylosing Spondylitis, Systemic Lupus Erythematosus, Wegener’s granulomatosus, Polyarteritis nodosa)
  • Herpes Zoster
  • Sarcoidosis
  • Inflammatory Bowel Disease
  • Gout

Systemic treatment with NSAIDs (or oral Prednisolone if severe)

  • Corticosteroid eye drops/ oral corticosteroids help reduce the inflammation. Consider investigating for or treating the underlying cause to prevent recurrence.

Subconjunc​tival haemorrhage

  • Diffuse or localised collection of blood under conjunctiva – looks alarming but resolves sponatenously within 10-14 days
  • Asymptomatic
  • Causes: Idiopathic, trauma, cough, sneezing, aspirin, hypertension

Subconjunctival Haemorrhage
Subconjunctival Haemorrhage. Image from Wikipedia


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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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