• Other serious sight-threatening conditions:
• Acute glaucoma — causes markedly increased intraocular pressure; it presents with pain in the eye, headache, and blurring of vision. Signs include:
• Ciliary injection.
• Eye feels rock hard and very painful.
• Fixed and mid-dilated pupil.
• Hazy cornea.
• Headache and vomiting.
• Markedly diminished vision.
• Keratitis — presents with a unilateral, painful, photophobic, injected eye. Signs include:
• Ciliary injection.
• Corneal ulceration — often seen as a white spot (ulcer may be dendritic when caused by herpes simplex).
• Visual impairment may be affected, depending on the site of the ulcer.
• Scleritis — characterized by severe pain. It is usually associated with headache; autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus; infections (rarely); and chemical injuries (rarely).
• Ocular trauma
• Penetrating eye injury or embedded foreign body.
• Acid or alkali burns to the eye.
• Non-sight-threatening causes
• Episcleritis — this is painful but essentially self limiting. Scleritis is much more serious.
• Infective conjunctivitis — this is more likely when:
• There is a history of close contact with another affected person.
• Symptoms of upper respiratory tract infection are present.
• The eyes are glued together by discharge after sleep, or mucopurulent discharge is seen on examination.
• Symptoms start in one eye then spread to the other.
• An enlarged lymph node in front of the ear is identified.
• Irritant conjunctivitis is likely when conjunctivitis is associated with an identifiable mechanical or irritant cause, such as a displaced contact lens, a foreign body or eyelashes rubbing against the surface of the eye, or a chemical splashing into the eye.
• Allergic conjunctivitis is likely when conjunctivitis is associated with itching and recurs after exposure to a known allergen.
• Superficial corneal injury is likely when eye pain follows trauma or possible trauma, and a foreign body is present. It is confirmed when an abrasion is seen after staining with fluorescein.
• Subconjunctival haemorrhage is asymptomatic and, other than redness, there are no other abnormal findings. The redness is well demarcated, does not cover the cornea, and obliterates conjunctival blood vessels.
• Rare neoplastic syndromes which mimic intraocular inflammation (masquerade syndromes), such as:
• Lymphoma.
• Leukaemia.
• Ocular melanoma.
• Metastases.

[Khaw et al, 2004; Yanoff and Duker, 2004; Gupta and Murray, 2006]