Red eye
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Synonyms and keywords: Bloodshot eye

# Overview
Red eye is one of the most common complaints managed by primary care physicians though in some cases it heralds a serious and life-threatening condition needing urgent referral to ophthalmologist. The etiology of red eye can be infectious, traumatic, inflammatory, allergic, autoimmune and rarely secondary to tumors. Red eye stems from pathologies of eye lid, conjunctiva, cornea, sclera and uvea. Signs and/or symptoms such as photophobia, pain, visual acuity, itchiness, foreign body sensation and if the condition is unilateral or bilateral, must be documented. Whenever a red flag is identified in a patient presenting with red eye, the clinician must refer the patient for a same-day ophthalmologist consult.

# Classification
There is no established system for the classification of red eye.

# Causes
- The cause of red eye is diagnosed through a comprehensive eye examination and patient's history. The most common cause of red eye is conjunctivitis and the most common etiology is viral. There are other causes though, and differential diagnosis must include other diseases such as corneal abrasion, blepharitis, subconjunctival hemorrhage, foreign body, iritis, keratitis, chemical burn, glaucoma, and scleritis that may confound the physician.
- Conjunctivitis, episcleritis and subconjunctival haemorrhage make up about 70% of the primary care red eye consultations.

## Sight-threatening causes
The most common causes of sight-threatening causes of red eye include
- Keratitis
- Scleritis
- Acute glaucoma
- Orbital cellulitis
- Foreign body trauma
- Chemical burns

# Differentiating Red eye from other Diseases
While evaluating patients presenting with red eye, a crucial step is to identify the patients that have sight-threatening causes. This can be evaluated by asking historical questions about associated symptoms and performing a complete ocular examination. Associated symptoms include:
- Pain
- Photophobia
- Visual acuity
- History of trauma or exposure
- History of secretion
- History of systemic symptoms

# Treatment
In patients presenting with red eye, it is important to take a full detailed history and physical examination. In assessment of patient's red eye, the diagnosis can be narrowed by distinguishing other associated symptoms.
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# Related Chapters
- List of eye diseases and disorders
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