Red Eye Clinical Presentation

Updated: Feb 25, 2022
  • Author: Robert H Graham, MD; Chief Editor: Andrew A Dahl, MD, FACS  more...
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History and Physical Examination

Obtain the following information:

  • Onset

  • Visual changes

  • Foreign body sensation

  • Trauma

  • Photophobia

  • Pain

  • Discharge, clear or colored

  • Prior episodes

  • Ophthalmologic history, including eye surgery

  • Bilateral or unilateral

  • Contact lens use

  • Comorbid conditions, such as collagen-vascular disease

Perform a complete ophthalmologic examination on all patients, to include the following:

  • Visual acuity (each eye should be tested separately)

  • Extraocular movements

  • Pen light examination (should test for pupil reactivity, pupil shape, discharge, pattern of injection, and corneal opacity)

  • Tests for direct and consensual photophobia

  • Slit-lamp examination (examine the cornea for edema, defects, or opacification with and without fluorescein) – Mastery of slit-lamp technique is a prerequisite for making the correct diagnosis

  • Anterior chamber evaluation should be performed for depth, cells, and flare

  • Intraocular pressure (IOP) measurements

  • Eyelid inspection with eversion

Certain signs help distinguish among the various causes of a red eye.


Conjunctivitis (see the image below) is the most common cause of red eye; it is characterized by vascular dilation of the superficial conjunctival blood vessels, cellular infiltration, and exudation. Patients with conjunctivitis usually do not experience visual changes or ocular pain. Conjunctivitis may be allergic, toxic, viral, or bacterial. Because it often is difficult to distinguish precisely among the different types, the clinician often assumes a bacterial cause if the etiology is unclear.

Conjunctivitis. Courtesy of Wikipedia Commons. Conjunctivitis. Courtesy of Wikipedia Commons.

Allergic conjunctivitis often presents with pruritus in individuals with a history of allergic disease. Viral conjunctivitis tends to be associated with enlarged, tender preauricular nodes, watery discharge, and upper respiratory tract infection. Viral conjunctivitis, particularly due to adenovirus infection, is highly contagious; proper hygiene and hand washing habits should be emphasized to all patients, roommates, colleagues, and coworkers. Bacterial conjunctivitis tends to be associated with a more mucopurulent or purulent discharge. Toxic conjunctivitis may result from episodic or chronic exposure to chemical irritants, some capable of causing significant ocular surface damage. It is essential to identify the toxin or chemical in cases of acute exposure in order to render appropriately aggressive treatment.


Blepharitis (see the image below) is often associated with conjunctivitis and may be caused by allergic, infectious, or dermatologic processes. Staphylococci are the most common etiologic organisms.

Blepharitis. Courtesy of Wikipedia Commons. Blepharitis. Courtesy of Wikipedia Commons.


Canaliculitis (see the image below) is characterized by a mildly red eye (usually unilateral) with slight discharge. Discharge can be expressed from the canaliculus. Actinomyces, herpes simplex virus, staphylococci, and pneumococci are the most common causative organisms. [15] Retained foreign bodies such as dacryoliths and silicone plastic punctal plugs also must be considered.

Canaliculitis of the left lower lid. Courtesy of P Canaliculitis of the left lower lid. Courtesy of Peter Rubin, MD, Director, Eye Plastics Service, Massachusetts Eye and Ear Infirmary, Harvard Medical School.


Keratitis can be of bacterial, viral, fungal, or parasitic origin. Patients may have decreased visual acuity and photophobia and often complain of severe eye pain. An epithelial defect may be evident on slit-lamp examination or may require fluorescein staining for visualization. Corneal inflammation or infection may be accompanied by anterior chamber reaction.

Bacterial keratitis (see the image below) is often associated with contact lens wear, particularly overnight wear. A mucopurulent discharge is often observed, as well as corneal opacity with conjunctival hyperemia and photophobia. Viral keratitis usually presents with watery discharge and a grayish corneal opacity with photophobia and foreign body sensation. Any opacification of the cornea in a red eye is considered to represent a corneal infection until proven otherwise so is an emergent condition. The opacification may or may not take up fluorescein. This condition warrants prompt ophthalmic evaluation.

This photograph depicts a child with a bilateral e This photograph depicts a child with a bilateral eye condition known as interstitial keratitis (IK), a stigma related to congenital syphilis.


Dacryocystitis (see the image below) is characterized by localized pain, edema, and erythema over the lacrimal sac at the medial canthus of the eye. It is usually unilateral. Often, purulent discharge from the puncta is noted. Staphylococci are the most common causative organisms. [16]

Acute dacryocystitis. Acute dacryocystitis.


Scleritis (see the image below) is universally accompanied by pain, especially with tenderness exacerbated by digital pressure. Gradual onset of red eye and insidious decrease in vision are typically noted. Recurrent episodes are common. Anterior chamber inflammation or posterior involvement may affect visual acuity. The globe is usually tender and the sclera swollen. Deep scleral injection is accompanied by inflammation of the overlying episclera and conjunctiva. Scleritis is bilateral in 50% of patients.

Scleritis. Courtesy of Wikipedia Commons. Scleritis. Courtesy of Wikipedia Commons.

A deep violet discoloration of the globe may be observed because of dilation of the deep venous plexus. The clinician must beware of the white eye because this may be due to ischemia. It is an ophthalmic condition that warrants prompt ophthalmologic referral. Most patients have some form of autoimmune condition.


In episcleritis, unlike conjunctivitis, the inflammation tends to be limited to isolated patches, not involving the eye diffusely. Dilated episcleral vessels are observed between the white sclera. Injection of the more superficial conjunctival vessels should be differentiated from that of the deeper violaceous episcleral vessels. Some more persistent cases may encompass the entire visible ocular surface, as well as more posterior episclera.

A history of recurrent episodes is common. Mild-to-moderate tenderness over the area of injection may be observed. Vision usually is unaffected. A watery discharge may be present. Patients should be examined for corneal complications (15%) and uveitis (7%). Episcleritis is usually a self-limited process, but ophthalmologic consultation is required if the condition is persistent or recurrent. A much smaller percentage of patients with episcleritis test positive for systemic autoimmune disease than do patients with scleritis.

Corneal injury

First and foremost, the patient’s eye should be stained with fluorescein to detect evidence of corneal abrasion (see the image below). Penetration of the globe should be excluded via thorough slit-lamp examination, IOP testing, and Seidel testing with a fluorescein strip, when indicated. The lid should always be everted to exclude retained foreign material.

Corneal abrasion. Corneal abrasion.


In iritis, the eye develops a perilimbal redness known as ciliary flush due to dilation of the radial vessels. In conjunctivitis, by way of comparison, the intensity of vascular engorgement decreases toward the limbus. Cells and flare are present in the anterior chamber and may be seen with the slit lamp under high magnification in specific light conditions. Visual acuity, direct and consensual photophobia, pain in the involved eye, posterior synechiae between the iris and lens, and keratitic precipitates on the endothelium may be observed.

The pupil of the affected eye is usually constricted and irregular if synechiae have formed. A mild watery discharge may be present. Iritis often is  unilateral or asymmetric. Complications include glaucoma, cataract formation, and macular dysfunction; ophthalmologic consultation is required. Unfortunately, iritis is often overlooked in the context of the overwhelmingly higher incidence of bacterial conjunctivitis, as well as a strong reluctance for primary care providers to prescribe topical steroids or even seek ophthalmologic evaluation for what might erroneously be perceived as a self-limited bacterial surface infection. Thus, significant damage can occur when iritis goes unnoticed by the first provider to encounter these patients.

Dry eye syndrome

In most cases of dry eye syndrome (DES), or keratoconjunctivitis sicca (KCS), the eye appears normal. On slit-lamp examination, decreased tear meniscus at the lower lid margin may be noted. [17] The corneal epithelium shows areas with varying degrees of fine punctate stippling in the interpalpebral fissure, which stain with rose bengal or fluorescein if more severely damaged.


Narrow-angle glaucoma is an ophthalmologic emergency. Patients complain of severely painful red eye. Visual acuity is reduced and worsens over time. Haloes around light are common owing to corneal edema. Patients are usually older than 50 years and frequently hyperopic with a short axial length and small anterior chamber depth. The pupil may be mid-dilated and may be nonreactive to light. Slit-lamp examination reveals corneal edema and a shallow anterior chamber with mild cells and flare.

IOP is elevated, usually to a level higher than 45 mm Hg (reference range, < 21 mm Hg). The anterior chamber angle may be very narrow. Nausea and vomiting are common. Gonioscopy should be performed to confirm the diagnosis and immediate referral made for appropriate medical and laser surgical therapy to create the essential peripheral iridotomy.


Pterygium is a benign conjunctival growth made of triangular band of fibrovascular tissue caused by long-term exposure to ultraviolet light, dust, and low humidity. It usually arises from the nasal side of the sclera. It may encroach onto the cornea (pterygium) or extend on either side of the cornea (pinguecula).

Subconjunctival hemorrhage

Subconjunctival hemorrhage may appear as a flat, thin hemorrhage or as a thick collection of blood. The most common visual manifestation is a bright red patch with relatively normal surroundings. There may be a history of red eye and, possibly, mild irritation; however, patients are usually asymptomatic. Slit-lamp examination reveals the precise location of the hemorrhage under the conjunctiva. The view of the sclera may be obscured by blood, which may be dark red if the collection is thick. [18]