Red eye is a catch all term for the inflamed or injected external appearance of the eye, for which there are many causes.
I like Jeff Mann’s approach to red eye — he breaks the causes down into 3 groups:
- extra-ocular causes (e.g. orbital cellulitis, cavernous sinus thrombosis, carotid-cavernous fistula, cluster headache)
- external eye disease (e.g. eye lid and conjunctival disease)
- internal eye disease (e.g. iritis, glaucoma)
Once an extra-ocular cause is excluded (this will be discussed in a later post), a helpful approach is to divide up the causes of red eye as follows:
- Painless — is there diffuse or localised redness?
The next step is to consider which structures are abnormal: Lid, conjunctiva, cornea, sclera, or anterior chamber?
Painless red eye
These can be classified according to whether the redness is diffuse or localised.
- usually this is an eyelid abnormality as most cases of conjunctivitis are painful: e.g. blepharitis, ectropion, trichiasis, entropion, eyelid lesion (e.g. tumour, stye)
- e.g. pterygium, corneal foreign body, ocular trauma, subconjunctival hemorrhage
If you’re stuck for a differential diagnosis, fall back on working through the anatomical components of the eye and running through a pathophysiological sieve.
Painful red eye
These can be classified according which structure is abnormal:
- abnormal cornea
- e.g. herpes simplex keratitis, corneal ulcer, marginal keratitis, corneal abrasion,
- abnormal eyelid
- e.g. chalazion/ stye, acute blepharitis, herpes zoster ophthalmicus
- diffuse conjunctival injection
- e.g. viral conjunctivitis, allergic conjunctivitis, bacterial conjunctivitis, dry eyes, acute glaucoma
- ciliary injection/ scleral involvement
- e.g. scleritis
- anterior chamber involvement
- e.g. acute anterior uveitis (iritis), hypopyon, hyphema
References and Links
- Ophthalmology Befuddler 002 — The Red Eye Challenge