Causes of red eye

There are many different causes of a red eye. After taking a full history and thoroughly examining the eyes, a management plan can be made.

Anterior uveitis


Inflammation of the iris and ciliary body

Risk factors:

  • Previous uveitis
  • Seronegative arthropathy, especially HLA B27 positive patients
  • Herpes zoster ophthalmicus
  • Syphilis
  • Tb 


Clinical features:

  • Young or middle aged patients
  • Pain worse when reading
  • Photophobia
  • Reduced visual acuity


On examination:

  • Pupil may be small and irregular (due to posterior synechiae - adhesions of iris to the lens)
  • On using slit lamp, anterior chamber may show:
    • cells (moving, white specks)
    • hypopyon - pus in anterior chamber
    • flare (looking through frosted glass)
  • keratic precipitates may be seen at the back of the cornea



  • Treat underlying cause if found.
  • Topical steroids
  • Mydriatics to prevent synechaie being formed which can cause acute glaucoma. 



    Hypopyon in anterior uveitis

    Acute angle closure glaucoma

    Acute angle closure glaucoma. Red arrow shows conjunctival injection and white arrow show fixed semi


    Due to occlusion of the angle where aqueous fluid is normally drained, therefore leading to a sudden increase in intraocular pressure.


    Clinical features:

    • Usually in patients over 50 yrs
    • Severe pain
    • Red eye
    • Haloes around lights
    • Reduced visual acuity
    • Fixed semidilated pupil not reactive to light
    • Eye feels hard on palpation
    • Hazy cornea
    • Systemic symptoms- headache, nausea, vomiting



    • Urgent ophthalmological referral to prevent visual loss
    • IV acetazolamide 500mg
    • Pilocarpine 4% topical to constrict pupil
    • To restore normal aqueous flow, a hole needs to be made in the iris. This can be done with a laser (iridotomy) or surgically (iridectomy)



    • Inflammation of white sclera itself
    • Usually very painful; significantly more redness present compared to episcleritis
    • Associated with other autoimmune conditions
    • Visual acuity may be affected
    • Management - may need immunosuppressants
    • Complications - corneal ulceration, intraocular inflammation 


    Diffuse conjunctival injection in scleritis


    Mild conjunctival injection
    • Inflammation of episclera
    • Mild eye irritation and redness
    • Normal visual acuity
    • Management - usually self limiting, but steroids may help 


    Corneal ulceration


    • Infection
    • Corneal abrasion
    • Contact lenses
    • Exposure keratopathy (ie a patient with facial nerve palsy who is unable to close eyelids).


    Clinical Features

    • Pain
    • Foreign body sensation
    • Mild to moderate red eye
    • Blurred vision 
    • Photophobia



    • Staining the cornea with fluorescein shows an area of corneal epithelial defect, and shows up yellow.



    • Viral infection- Topical acyclovir
    • Bacterial or fungal infection- Broad spectrum antibiotics
    • Non-infectious ulcer- treat the cause.


    Corneal ulcer

    Subconjunctival haemorrhage

    Subconjunctival haemorrhage

    Bright red blood between white sclera and conjunctiva. Usually benign

    Can be caused by:

    • Severe coughing or straining
    • Hypertension
    • Blood disorders
    • Idiopathic


    Clinical features:

    • Diffuse area of bright red blood
    • May be a foreign body
    • No pain, blurred vision or photophobia
    • Eye examination otherwise normal



    • Exclude hypertension
    • Check coagulation profile, especially if patient is on warfarin
    • Reassure patients that it is benign and may take a few weeks to fade




    ABC of Eyes. 4th edition.

    Kennerley Banke's Clinical Ophthalmology. 4th ediition.

    Image 1- Hypopyon in anterior uveitis taken from http://2.bp.blogspot.com/_LMdPu119VcY/TUvZrm6K2MI/AAAAAAAAAac/nJx_-lny8tU/s1600/ant+uveitis.jpg

     Image 2- Acute angle closure glaucoma taken from http://www.medrounds.org/glaucoma-guide/2006/12/section-9-c-diagnosis-of-acute-angle.html

    Image 3- Scleritis taken from http://eyepathologist.com/images/KL21711.jpg

    Image 4- Episcleritis taken from http://www.gp-training.net/protocol/ophthalmology/redeye/episcl.jpg

    Image 5- Corneal ulcer taken from http://www.revophth.com/CMSImagesContent/2004/9/1_588_0.jpg

    Image 6- Subconjunctival haemorrhage taken from http://www.tedmontgomery.com/the_eye/eyephotos/pics/SubconjunctivalHemorrhage.jpg


    Fastbleep © 2019.