Red eye refers to a red appearance of the opened eye, reflecting dilation of the superficial ocular vessels.
Pathophysiology of Red Eye
Dilation of superficial ocular vessels can result from
Infection
Allergy
Inflammation (noninfectious)
Elevated intraocular pressure (less common)
Several ocular components may be involved, most commonly the conjunctiva, but also the uveal tract, episclera, and sclera.
Etiology of Red Eye
The most common causes of red eye include
Corneal abrasions and foreign bodies are common causes (see table Some Causes of Red Eye). Although the eye is red, patients usually present with a complaint of injury, eye pain, or both. However, in young children and infants, this information may be unavailable.
Evaluation of Red Eye
Most disorders can be diagnosed by a general health care professional.
History
History of present illness should note the onset and duration of redness and presence of any change in vision, itching, scratchy sensation, pain, or discharge. Nature and severity of pain, including whether pain is worsened by light (photophobia), are noted. The clinician should determine whether discharge is watery or purulent. Other questions assess history of injury, including exposure to irritants and use of contact lenses (eg, possible overuse, such as wearing them while sleeping). Prior episodes of eye pain or redness and their time patterns are elicited.
Review of systems should seek symptoms suggesting possible causes, including headache, nausea, vomiting, and halos around lights (acute angle-closure glaucoma); runny nose and sneezing (allergies, upper respiratory infection); and cough, sore throat, and malaise (upper respiratory infection).
Past medical history includes questions about known allergies and autoimmune disorders. Medication history should specifically ask about recent use of topical ophthalmic medications (including over-the-counter medications), which might be sensitizing.
Physical examination
General examination should include head and neck examination for signs of associated disorders (eg, upper respiratory infection, allergic rhinitis, zoster rash).
Red flags
The following findings are of particular concern:
Sudden, severe pain and vomiting
Zoster rash
Decreased visual acuity
Corneal crater
Branching, dendritic corneal lesion
Ocular pressure > 40 mm Hg
Interpretation of findings
Conjunctival disorders and episcleritis are differentiated from other causes of red eye by the absence of pain, photophobia, and corneal staining. Among these disorders, episcleritis is differentiated by its focality, and subconjunctival hemorrhage is usually differentiated by the absence of lacrimation, itching, and photosensitivity. Clinical criteria do not accurately differentiate viral from bacterial conjunctivitis.
Corneal disordersanterior uveitis, glaucoma, or scleritis. Because patients may have anterior uveitis secondary to corneal lesions, persistence of pain after instillation of the anesthetic does not exclude a corneal lesion.
Anterior uveitis, acute angle-closure glaucoma, and scleritis
Pearls & Pitfalls
scleritis. Phenylephrine is instilled to dilate the pupil in patients needing a thorough retinal examination. However, it should not be used in patients who have the following:
Suspected acute angle-closure glaucoma
A history of angle-closure glaucoma
A narrow anterior chamber
Testing
Testing is usually unnecessary. Viral cultures may help if herpes simplex or herpes zoster is suspected and the diagnosis is not clear clinically. Corneal ulcers are cultured by an ophthalmologist. Gonioscopy is done in patients with glaucoma. Testing for autoimmune disorders may be worthwhile in patients with uveitis and no obvious cause (eg, trauma). Patients with scleritis undergo further testing as directed by an ophthalmologist.
Treatment of Red Eye
The cause is treated. Red eye itself does not require treatment. Topical vasoconstrictors are not recommended.
Key Points
Most cases are caused by conjunctivitis.
Pain and true photophobia suggest other more serious diagnoses.
