Differential Diagnosis of Red Eye
Viral conjunctivitis (most common cause of red eye)
Allergic / irritant conjunctivitis
Bacterial conjunctivitis
Neonatal Conjunctivitis (Ophthalmia Neonatorum)
Blepharitis
Hordeolum (Stye)
Chalazion
Bacterial Endophthalmitis
Fungal Endophthalmitis
Keratitis (Corneal inflammation) -Bacterial or viral
Subconjunctival hemorrhage
Corneal abrasion
Corneal Ulcer
Foreign body
Dry eye disease (Keratoconjunctivitis sicca)
Contact lens complications / overwear
Episcleritis
Trauma
Herpes zoster
Chlamydia
Iritis (acute anterior uveitis)
Glaucoma (Acute angle-closure glaucoma)
Chemical burn
Scleritis
Hyperthyroidism
Cluster headache
Corneal Graft Rejection
Pterygium
Orbital Cellulitis
Preseptal Cellulitis
Postoperative Endophthalmitis
Ectropion (out-turning of the eyelid)
Entropion (in-turning of the eyelid)
Giant Papillary Conjunctivitis
Ophthalmologic Manifestations of Kaposi Sarcoma
Stevens-Johnson Syndrome
Dacryocystitis (infection of the lacrimal sac, 2/2 a nasolacrimal duct obstruction)
Acute Hemorrhagic Conjunctivitis
Distichiasis
Myositis / idiopathic orbital inflammatory pseudotumor
Thinking about the differential diagnosis
What is the difference between preseptal and orbital cellulitis?
Further Reading
Am Fam Physician. 2016 Jun 15;93(12):991-998. https://www.aafp.org/afp/2016/0615/p991.html
Am Fam Physician. 2010 Jan 15;81(2):137-144. https://www.aafp.org/afp/2010/0115/p137.html
https://emedicine.medscape.com/article/1192122-differential?src=refgatesrc1