Red eye

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Differential Diagnosis

  • Conjunctivitis - common eye infection affecting the conjunctiva
  • Glaucoma - increase in intraocular pressure. The dangerous one is closed-angle glaucoma. The rest are less of an issue. Acute glaucoma is due to the pupil getting caught on the lens which blocks aqueous outflow. As such, it often happens when the pupil is mid-dilation e.g. during stress or excitement, watching TV in dim lighting, in patients on mydriatics
  • Iritis - infection of the iris (aka anterior uveitis). Important as acutely it can send you blind.
  • Dry eyes - lack of tear production
  • Local trauma/foreign bodies - having a log in your eye. Well accordingly to that dumbass parable in the Bible.
  • Lid disorders

Clinical and Associated Features

The first thing to do is identify an emergency red eye.

  • Conjunctivitis - usually bilateral, can be painful, some photophobia, normal - acuity, cornea, pupil, intraocular pressure
  • Iritis aka anterior uveitis - acute, photophobia, blurred vision, crying, whole eye goes red, small pupil (iris spasm). Talbot's test - pain gets worse on convergence. Tell patient to look at your finger and move it towards their face.
  • Closed-angle glaucoma - visual disturbance (leading to visual loss), eye pain (can be in the eye, around the orbit or just a generalised frontal headahce), nausea & vomiting.
  • Dry eyes - there will be no tears
  • Trauma/foreign body - should be fairly obvious


  • Conjuctivitis - chloramphenical for infection. Antihistamine eye drops for allergic. Refer for chlamydia.
  • Iritis - refer to opthalmologist. Steroids (prednisolone drops 0.5% every 2h & cyclopentolate 0.5% 2 drops/6h)
  • Closed-angle glaucoma - pilocarpine 4% drops hourly, acetazolamide 500mg po stat (iv if vomiting) & 250mg/8h po/iv. Surgery may also be required.