Red Eye | red eyes and disease | Effect of red eye | what causes red eyes

Red Eye

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

·         Infectious conjunctivitis

·         Allergic conjunctivitis

·         Corneal abrasions and foreign bodies are common causes . 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.

 

TABLE

Some Causes of Red Eye         

Evaluation of Red Eye

Most disorders can be diagnosed by a general health care practitioner.

 

 

Physical examination

General examination should include head and neck examination for signs of associated disorders (eg, upper respiratory infection, allergic rhinitis, zoster rash).

 

Eye examination involves a formal measure of visual acuity and usually requires a penlight, fluorescein stain, and slit lamp.

 

Best corrected visual acuity is measured. Pupillary size and reactivity to light are assessed. True photophobia (sometimes called consensual photophobia) is present if shining light into an unaffected eye causes pain in the affected eye when the affected eye is shut. Extraocular movements are assessed, and the eye and periorbital tissues are inspected for lesions and swelling. The tarsal surface is inspected for papillae. The corneas are stained with fluorescein and examined with magnification. If a corneal abrasion is found, the eyelid is everted and examined for hidden foreign bodies. Inspection of the ocular structures and cornea is best done using a slit lamp. A slit lamp is also used to examine the anterior chamber for cells, flare, and pus (hypopyon). Ocular pressure is measured using tonometry, although it may be permissible to omit this test if there are no symptoms or signs suggesting a disorder other than conjunctivitis.

 

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

·         Failure to blanch with phenylephrine eye drop

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 disorders are differentiated from other causes of red eye (and usually from each other) by fluorescein staining. These disorders also tend to be characterized by pain and photophobia. If instillation of an ocular anesthetic drop (eg, proparacaine 0.5%), which is done before tonometry and ideally before fluorescein instillation, completely relieves pain, the cause is probably limited to the cornea. If pain is present and is not relieved by an ocular anesthetic, the cause may be anterior 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 can usually be differentiated from other causes of red eye by the presence of pain and the absence of corneal staining. Anterior uveitis is likely in patients with pain, true photophobia, absence of corneal fluorescein staining, and normal intraocular pressure; it is definitively diagnosed based on the presence of cells and flare in the anterior chamber. However, these findings may be difficult for general health care practitioners to discern. Acute angle-closure glaucoma can usually be recognized by the sudden onset of its severe and characteristic symptoms, but tonometry is definitive.

 

Pearls & Pitfalls

If pain persists despite an ocular anesthetic in a patient with a normal fluorescein examination, consider anterior uveitis, scleritis, or acute angle-closure glaucoma.

Instillation of phenylephrine 2.5% causes blanching in a red eye unless the cause is 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.

·         In patients with pain, slit-lamp examination with fluorescein staining and tonometry are key.

·         Persistence of pain despite an ocular anesthetic in a patient with a normal fluorescein examination suggests anterior uveitis, scleritis, or acute angle-closure glaucoma.