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Those with sore eyes … find the light painful, while the darkness, which permits them to see nothing, is restful and agreeable.

Dio Chrysostom (40–115)


A red eye accounts for at least 80% of patients with eye problems encountered in general practice.1 An accurate history combined with a thorough examination will permit the diagnosis to be made in most cases without recourse to specialist ophthalmic equipment. A summary of the diagnostic strategy model is presented in Table 51.1.

Table Graphic Jump Location
Table 51.1

The red and tender eye: diagnostic strategy model


Key facts and checkpoints

  • Acute conjunctivitis accounts for over 25% of all eye complaints seen in general practice.2

  • A purulent discharge indicates bacterial conjunctivitis.3

  • A clear or mucous discharge indicates viral or allergic conjunctivitis.

  • Viral conjunctivitis can be slow to resolve and may last for weeks.

  • Pain and visual loss suggest a serious condition such as glaucoma, uveitis (including acute iritis) or corneal ulceration.

  • Beware of the unilateral red eye—think beyond bacterial or allergic conjunctivitis. It is rarely conjunctivitis and may be a corneal ulcer, keratitis, foreign body, trauma, uveitis or acute glaucoma.4

  • Keratitis (inflammation of the cornea) is one of the most common causes of an uncomfortable red eye. Apart from the well-known viral causes (herpes simplex, herpes zoster, adenovirus and measles), it can be caused by fungal infection (usually on a damaged cornea), bacterial infection or inflammatory disorder such as ankylosing spondylitis.5

  • Herpes simplex keratitis (dendritic ulcer) often presents painlessly as the neurotrophic effect grossly diminishes sensation.


The clinical approach


The five essentials of the history are:


  • history of trauma, especially as indicator of intra-ocular foreign body (IOFB)

  • vision

  • the degree and type of discomfort

  • presence of discharge

  • presence of photophobia


The social and occupational history is also very important. This includes a history of exposure to a ‘red eye’ at school, work or home; incidents at work such as injury, welding, foreign bodies or chemicals; and genitourinary symptoms.


When examining the unilateral red eye keep the following diagnoses in mind:


  • trauma

  • foreign body, including IOFB

  • corneal ulcer

  • iritis (uveitis)

  • viral conjunctivitis (commonest type)

  • acute glaucoma



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