Version July 2025
INTRODUCTION —
"Red eye" is a common presenting complaint in ambulatory practice. A small percentage of affected patients need urgent ophthalmologic referral and treatment, although the vast majority can be treated by the primary care clinician. There are little epidemiologic data on the red eye and no evidence-based data to guide the management of these patients. Conjunctivitis (allergic or viral) is probably the most common cause of red eye in the community setting, but a number of more serious conditions can also occur [1,2].
This topic presents an approach for distinguishing patients with red eye who must be referred to an ophthalmologist (table 1), such as those with angle-closure glaucoma, from patients who can be managed by the primary care clinician (table 2), such as those with allergic conjunctivitis. Distinguishing features of conditions presenting as a red eye are summarized in the table (table 3). The specific diagnosis and treatment of many of these disorders are discussed separately.
●(See "Eyelid lesions".)
●(See "Blepharitis".)
●(See "Allergic conjunctivitis: Clinical manifestations and diagnosis".)
●(See "Infectious conjunctivitis".)
●(See "Conjunctival injury", section on 'Subconjunctival hemorrhage'.)
●(See "Corneal abrasions and corneal foreign bodies: Clinical manifestations and diagnosis".)
●(See "Angle-closure glaucoma".)
●(See "Uveitis: Etiology, clinical manifestations, and diagnosis".)
PATIENT EVALUATION —
Patient history, measurement of visual acuity, and findings on penlight examination are important in determining the cause and management of red eye and provide guidance in deciding whether to refer the patient for ophthalmologic evaluation.
Determining who needs to be seen in person — Many patients with a red eye call to inquire whether they need an in-person office visit. Certain historical features or presenting complaints signal the need for in-person examination and possibly patient referral. However, many cases can be handled by primary care providers by telephone, telemedicine (video), or by having the patient send phone images [3]. There is emerging evidence that virtual consultation for red eye results in accurate diagnosis and can result in decreased need for in-person visits [4].
The following questions should be asked of all patients. If the answer to any of the following questions below is yes, a sight-threatening process is more likely, and in-person evaluation or referral to an ophthalmologist is warranted:
●Is your vision affected? – Can you still read ordinary print with the affected eye? Patients with impaired vision cannot be managed by telephone or telemedicine; they require a clinician examination and may, depending upon the findings, require ophthalmological referral.
●Is there pain that is acute in onset, progressive, not relieved by analgesia, or interfering with sleep? – If the patient has acute, progressive, or severe pain, more serious conditions such as angle-closure glaucoma, bacterial keratitis, iritis (also known as anterior uveitis), or scleritis should be considered. (See 'Serious conditions' below.)
●Are you able to open your eye? – Does it feel as though there is something in your eye, preventing you from opening, or keeping your eye open (foreign body sensation)? A foreign body sensation is the cardinal symptom of a corneal process.
•Objective evidence of foreign body sensation, in which the patient is unable to spontaneously open the eye or keep it open, suggests corneal involvement, which may indicate a serious or potentially vision-threatening condition (see 'Bacterial keratitis' below). With the exception of the initial presentation for corneal abrasion or foreign body, such patients warrant emergent or urgent referral to an ophthalmologist. (See 'Corneal abrasions' below.)
•Subjective foreign body sensation, in contrast, is commonly reported as a "scratchy feeling," "grittiness," or a sensation "like sand in my eyes" with allergy, viral conjunctivitis, or dry eyes. The patient can open the eye spontaneously and keep it open. This does not necessarily suggest a corneal problem that requires referral. (See 'Conjunctivitis' below.)
●Are you sensitive to bright light? – Patients with photophobia should always be examined by a clinician. Photophobia may indicate an inflammatory process such as iritis or scleritis, or a corneal condition, such as an abrasion or keratitis (inflammation or breakdown of the cornea, eg, from viral or bacterial infection).
●Have you had recent trauma, eye surgery, or contact lens wear? – Trauma can cause hyphema or iritis, while recent eye surgery should prompt consideration of complications. A history of contact lens wear in the setting of discharge and a red eye should increase the suspicion of bacterial keratitis [5]. (See 'Serious conditions' below and "Complications of contact lenses", section on 'Infectious keratitis'.)
●Do you have double vision when both of your eyes are open, that resolves when you close either one of your eyes? – Ask the patient to first close the right eye (and note if the double vision resolves), and then repeat with the left eye. If the answer is yes in both cases, the patient has binocular diplopia and serious conditions affecting ocular motility, such as orbital cellulitis or cranial nerve palsy, should be considered. (See "Orbital cellulitis" and "Third cranial nerve (oculomotor nerve) palsy in adults".)
Determining severity and need for referral
General observation — General observation and further history from the patient can provide guidance as to whether the problem is likely to be benign and treatable initially by the primary care clinician or if it requires referral. Although the subjective report of symptoms and threshold to report symptoms varies among individuals, general patient observation can provide reliable clues.
●The patient with infectious keratitis, iritis, or angle-closure glaucoma is likely to have objective signs indicating the more serious nature of the problem. Patients may appear generally uncomfortable and may have nausea or vomiting in the case of angle-closure glaucoma. Physical examination may reveal ciliary flush, which is redness localized to the limbus (the transition zone between cornea and sclera), or tenderness on palpation of the eyeball (with gentle pressure applied while the eye is closed). (See 'Serious conditions' below.)
●Patients should be observed for signs of photophobia. Patients with photophobia may present wearing a hat and/or sunglasses, covering the affected eye with the hand to block out light, or keeping the head down and turned away from light fixtures or windows. They may request that the examination room lights be left off while waiting for the provider. Photophobia may suggest an inflammatory process such as iritis or a corneal process (in which objective foreign body sensation will also be present).
●Conditions limited to the eyelids or conjunctiva, and other common benign conditions, do not cause objective foreign body sensation or photophobia. The patient is comfortable sitting in the examination room with both eyes open, unaffected by the ambient lighting. The patient with viral or allergic conjunctivitis may have signs of rhinorrhea, lymphadenopathy, or other upper respiratory tract symptoms.
Eye examination
Visual acuity
●Measurement – Visual acuity should be assessed in every patient who is evaluated in-person for an eye complaint. Each eye should be tested separately. This measurement should be made before lights are shined in the eye or any drops are applied.
Snellen acuity is the standard; however, this test requires using a Snellen chart at 20 feet with best correction or pinhole and may be difficult to perform. An alternative in a triage setting is measurement of near vision. Allow the patient to use their usual reading correction if possible and hold a near card or ordinary book, newspaper, or magazine at a comfortable distance. It is not important to determine exactly whether the vision is 20/30 or 20/40 at 12 or 14 inches, but rather to document visual acuity in crude categories: reading vision (small versus large print); form vision only (hand motions or count fingers); or light perception.
●Significance of results – The presence of normal acuity is reassuring and supports a diagnosis of a benign condition and initiation of therapy by the primary care clinician. On the other hand, if acuity of the red eye is reduced beyond that which the patient reports is typical, the primary care clinician should suspect one of the more worrisome diagnoses, eg, infectious keratitis, iritis, or angle-closure glaucoma, and refer the patient for ophthalmology evaluation and therapy.
Penlight examination — A penlight or light from another source, such as a cell phone, should be used to examine the pupils and anterior segment. A slit lamp is not required to distinguish those entities that can be treated by the primary care clinician from those entities that must be referred. It is useful to consider the following questions during the penlight examination:
●Does the pupil react to light? – The pupil is fixed in mid-dilation in cases of angle-closure glaucoma. It does not react to light and is typically 4 to 5 mm in diameter.
●Is the pupil very small (1 to 2 mm)? – The pupil may be pinpoint in cases of corneal abrasion, infectious keratitis, or iritis (due to inflammation of the ciliary body, which causes pupil constriction). Abrasion is distinguished from iritis by the presence of a staining defect on fluorescein examination and an objective foreign body sensation, neither of which are present with iritis. Traumatic iritis may occur after blunt trauma such as from a softball or fist, but there are no corneal findings.
●Is there discharge?
•Watery discharge present throughout the day is found in many self-limited processes such as stye or hordeolum, viral conjunctivitis, allergic conjunctivitis, and dry eyes. Patients may also have scant amounts of crusting in the morning. (See 'Conjunctivitis' below.)
•Opaque or purulent discharge may suggest bacterial conjunctivitis or bacterial keratitis. In conjunctivitis, there are no opacities by penlight or staining defects with fluorescein.
-Bacterial conjunctivitis is typically not associated with a reduction in visual acuity, foreign body sensation, or photophobia, and may be treated by the primary care clinician. (See "Infectious conjunctivitis".)
-Bacterial keratitis, on the other hand, may or may not affect vision but typically causes objective foreign body sensation and photophobia and requires emergency referral. (See 'Bacterial keratitis' below.)
●What is the pattern of redness? – Diffuse injection involving both the conjunctiva inside the lid (the palpebral conjunctiva) and the conjunctiva on the globe (the bulbar conjunctiva) suggests a primary conjunctival problem such as conjunctivitis. Conjunctivitis may be bacterial, viral, allergic, toxic, or nonspecific. In these entities, the entire mucus membrane is equally involved. By comparison, ciliary flush is characteristic of more serious entities including infectious keratitis, iritis, or angle closure. With ciliary flush, injection is most marked at the limbus (where the cornea undergoes transition to the sclera) and then diminishes toward the equator (picture 1).
When the redness appears hemorrhagic rather than in a pattern of injection (dilated blood vessels), the diagnosis of subconjunctival hemorrhage should be considered. (See 'Subconjunctival hemorrhage' below.)
●Is there a white spot, opacity, or foreign body on the cornea? – A white spot or opacity on the cornea suggests infectious keratitis. This can usually be seen without using fluorescein. If available, fluorescein can be used at the end of the examination to confirm the absence or presence of a corneal process. The white spot of a bacterial keratitis and the raised, grayish branching opacity of herpes simplex keratitis will pick up stain (picture 2). Abrasions will also pick up stain; however, these are not characterized by the presence of corneal opacity. A corneal foreign body will not pick up stain.
●Is there hypopyon or hyphema? – Hypopyon, a layer of white blood cells in the anterior chamber, or hyphema, a layer of red blood cells, each require urgent referral to an ophthalmologist (picture 3 and picture 4). Hypopyon is associated with sight-threatening infectious keratitis or endophthalmitis until proven otherwise; these patients must be seen by an ophthalmologist within hours. Hyphema is a sign of blunt or penetrating trauma to the globe and must also be seen by an ophthalmologist within hours to evaluate for penetrating eye injury, retinal detachment, and acute glaucoma. (See "Traumatic hyphema: Clinical features and diagnosis".)
Role of fundus examination — A fundus examination is important if red eye occurs in the presence of facial swelling or vesicular eruption respecting the midline, proptosis, or nonreactive pupil to determine if there is optic nerve involvement.
However, in most patients the fundus examination is typically not helpful in the differential diagnosis of the red eye or too difficult to perform. In benign entities such as lid and conjunctival processes, the fundus examination is easily performed but has no associated pathologic features. In iritis and keratitis, the pupil is very small and the patient is often photophobic, making the examination difficult to perform. Although the pupil is midsize in angle-closure glaucoma, the fundus examination becomes increasingly difficult to perform as the attack persists due to increasing corneal cloudiness from high intraocular pressure.
ETIOLOGY AND MANAGEMENT —
The differential diagnosis of the red eye includes serious conditions that require emergent or urgent ophthalmologic evaluation (table 1) and benign conditions (table 2). As described above, features that can help distinguish these conditions include history, visual acuity, foreign body sensation, photophobia, discharge, pupil size and reactivity, pruritus or pain, and fluorescein staining (table 3).
Serious conditions — Conditions that require emergency (same day) or urgent (within one to two days) ophthalmologic referral are summarized anatomically, from anterior to posterior (figure 1) in the following section and in the table (table 1).
Emergency (same day) referral — The following conditions are rapidly vision threatening and require same day ophthalmologic evaluation.
Infectious keratitis — Infectious keratitis (inflammation of the cornea) can be caused by bacteria, viruses, fungi, or parasites [6]. One report estimated that in the United States there are nearly one million visits to outpatient clinics or emergency departments for keratitis or contact lens disorders annually [7]. Of infectious causes of keratitis, bacterial keratitis requires emergent ophthalmology referral, while viral keratitis warrants urgent evaluation. (See "Complications of contact lenses", section on 'Infectious keratitis' and 'Viral keratitis' below.)
Bacterial keratitis — Bacterial infectious keratitis warrants evaluation by an ophthalmologist on the same day. The patient will have objective foreign body sensation and have trouble keeping the involved eye open, a sign of an active corneal process. Decreased visual acuity may also be present. Bacterial pathogens include Staphylococcus aureus, Pseudomonas aeruginosa, coagulase-negative Staphylococcus, diphtheroids, Streptococcus pneumoniae, and polymicrobial isolates [8].
The diagnostic finding in bacterial keratitis is a corneal opacity or infiltrate (typically a round white spot) (picture 5) in association with red eye, photophobia, and foreign body sensation. This infiltrate or ulcer (>0.5 mm in size) may be seen with a penlight and does not necessarily require a slit lamp for identification. It will stain with fluorescein. Mucopurulent discharge is typically present. Fulminant cases may present with an associated hypopyon (layer of white cells in the anterior chamber) (picture 3).
Improper contact lens wear is the biggest risk factor for bacterial keratitis [7]. Overnight or extended wear of contact lenses is associated with a higher incidence of bacterial keratitis, but keratitis can also occur in patients who do not wear contact lenses or who wear them on a daytime-only basis. Breakdown in local or systemic host defense mechanisms, including dry eye or ocular surface disease, topical corticosteroid use, and immunosuppression, can predispose to bacterial keratitis.
Treatment requires emergent ophthalmological referral and prompt initiation of topical antibiotics (ideally after obtaining cultures). These antibiotics are sometimes compounded in fortified concentrations and are not commercially available. The role of topical glucocorticoids and topical drug combinations containing topical steroids is controversial and best left to the discretion of the consulting ophthalmologist [8-11]. (See "Complications of contact lenses", section on 'Infectious keratitis'.)
Hyphema — Hyphema refers to the finding of red blood cells layered in the bottom of in the anterior chamber (picture 4). This finding warrants same-day evaluation by an ophthalmologist as it can be associated with significant trauma, inflammation, or pathologic neovascularization. (See "Traumatic hyphema: Clinical features and diagnosis" and "Traumatic hyphema: Management".)
Hypopyon — Hypopyon refers to the finding of white blood cells layered in the bottom in the anterior chamber (picture 3). This finding warrants same-day evaluation by an ophthalmologist as it can be associated with infectious keratitis or endophthalmitis. (See "Bacterial endophthalmitis".)
Angle-closure glaucoma — Acute angle-closure glaucoma is relatively uncommon, but the incidence increases dramatically with age [12]. Angle closure leads to a sudden increase in intraocular pressure, which causes pain, nausea, and decreased visual acuity (figure 2A-B). The patient with angle-closure glaucoma typically appears to be in general distress. They may be slumped over, covering the eye or clutching the frontal or temporal region of the head (masking the red eye), and reporting primarily headache and malaise. As angle closure progresses and the intraocular pressure rises, patients develop nausea and, in some cases, vomiting. The pain of angle closure is a dull ache that is more likely reported as unilateral headache, rather than eye pain. Some patients describe "the worst headache in my life" and may not attribute their symptoms to the eye. (See "Angle-closure glaucoma".)
The severity of headache may trigger extensive neurologic workup and imaging that may critically delay ophthalmologic treatment. This can be avoided by specifically assessing for a red eye and associated ocular findings. Visual acuity becomes increasingly reduced as the duration of the attack increases. Patients may also report seeing a bright “halo” around lights. Patients may be photophobic, though they do not typically have foreign body sensation.
Penlight examination reveals a red eye with ciliary flush and no discharge. The pupil is fixed in mid-dilation and the anterior chamber is shallow. Within hours of symptom onset, the cornea becomes hazy (picture 1). Corneal haziness may be detected as a loss of appreciable detail in the iris. Diagnosis is confirmed with measurement of intraocular pressure. Normal intraocular pressure is 8 to 22 mmHg; pressures in acute angle closure are often greater than 45 mmHg. The eye may feel “rock hard” to palpation with eyelids closed.
Angle-closure glaucoma is a sight-threatening emergency that must be treated within hours to avoid irreversible damage to the optic nerve. Typically, pressure-lowering topical and systemic agents are administered, and definitive treatment in the form of laser iridotomy is performed that same day by the ophthalmologist. The fellow eye is then treated prophylactically within days.
Urgent (1 to 2 day) referral — The following conditions can be vision-threatening but are more indolent processes. Therefore, urgent ophthalmologic evaluation within one to two days is appropriate.
Viral keratitis — A number of viruses, including herpes simplex, herpes zoster, mpox, and some strains of adenovirus, can cause viral keratitis.
●Herpes simplex – Herpes simplex causes viral keratitis characterized by red eye, photophobia, foreign body sensation, and watery discharge. There may be a faint branching grey opacity on penlight examination (picture 6). This branching opacity is best visualized with application of fluorescein. Although typically a self-limited process, duration of symptoms is reduced with treatment with topical or oral antiviral agents. Patients should be referred to an ophthalmologist within a few days for confirmation of diagnosis, initiation of therapy, and monitoring for response, sequelae, or recurrence. Immunocompromised patients may require topical and systemic treatment and longer duration of therapy. A small percentage of patients develop chronic or recurrent inflammation, or recurrent viral keratitis, both of which are treated with prophylactic oral antiviral agents. Some patients also benefit from treatment with topical corticosteroid agents, used in conjunction with antiviral prophylaxis, under the care of an ophthalmologist. (See "Herpes simplex keratitis".)
●Herpes zoster – Herpes zoster affecting the ophthalmic division of the trigeminal nerve is called herpes zoster ophthalmicus (HZO). HZO typically presents as a vesicular rash respecting the midline and affecting the forehead, periorbital region, and nose. It is sometimes associated with periorbital edema. All patients with HZO require immediate systemic antiviral therapy to reduce the likelihood of postherpetic neuralgia. Not all patients with HZO have ocular involvement (of the eyeball itself), which may occur one to two weeks after the initial presentation. Patients with HZO and ocular involvement, eg foreign body sensation, photophobia, and fluorescein staining (which may suggest keratitis or iritis), should be referred to an ophthalmologist. If there is vision loss associated with HZO, then urgent ophthalmologic evaluation within one to two days is warranted to assess for keratitis, iritis, or for rare complications including acute retinal necrosis or optic neuropathy. Additional treatment with topical antivirals and corticosteroids, and in some cases, intravenous antivirals, may be required depending on the type of involvement.
●Adenovirus – Adenovirus typically causes conjunctivitis, but some strains in some individuals can cause an associated keratitis (epidemic keratoconjunctivitis [EKC]). These patients have classic manifestations of viral conjunctivitis but within a few days develop symptoms of an active corneal process (photophobia and objective foreign body sensation). Penlight examination of the cornea is unremarkable, but fluorescein staining reveals multiple punctate staining lesions. Preauricular lymphadenopathy is often present.
EKC or adenoviral keratitis is typically a self-limited process without sequelae, although patients are quite miserable during active disease because of photophobia and foreign body sensation. Referral to an ophthalmologist within days is warranted for confirmation of the diagnosis, for monitoring for resolution, and for treatment if there is decline in vision from centrally located viral lesions. (See "Diagnosis, treatment, and prevention of adenovirus infection".)
Iritis (anterior uveitis) — Inflammation of the anterior uveal tract is called iritis (also known as anterior uveitis); when the adjacent ciliary body is also inflamed, the process is called iridocyclitis. (See "Uveitis: Etiology, clinical manifestations, and diagnosis".)
Patients with iritis may present with eye redness, pain, and photophobia. Decreased visual acuity may be present. The patient may choose to keep the eyes closed to block out light but, in a dimly lit environment, the patient is able to keep the affected eye open spontaneously. Patients with iritis will display an aversive response when the penlight is shined in the affected and in the uninvolved eye.
The cardinal sign of iritis is ciliary flush: injection that gives the appearance of a red ring around the iris. Typically, there is no discharge and only minimal tearing. The pupil is typically very small (unless dilating eye drops have been given), and occasionally can be irregularly shaped due to inflammatory adhesions (picture 7). Corneal abrasion should be ruled out with fluorescein staining, and angle closure should be ruled out by confirming that the pupil is not fixed in mid-dilation. The diagnosis is presumptive until presence of inflammatory cells or exudative “flare” is confirmed by slit lamp examination.
Iritis can be caused by any one of many infections, inflammatory, and infiltrative processes. These include tuberculosis, sarcoidosis, syphilis, toxoplasma, toxocara, and reactive arthritis. Many cases are idiopathic.
Patients with iritis should be seen by an ophthalmologist in one to two days. The ophthalmologist will initiate treatment, typically with topical steroids, and monitor for side effects and response to therapy. Cases that are bilateral, recurrent, sight-threatening, or non-responsive to therapy require extensive work-up to determine the etiology and need for specific therapy.
Scleritis — Scleritis is a painful, destructive, and potentially vision-threatening disorder that may also involve the cornea, adjacent episclera, and underlying uveal tract. Scleritis has a striking, highly symptomatic clinical presentation (picture 8). Scleritis is usually characterized by constant, boring pain that worsens at night or in the early morning hours and radiates to the face and periorbital region. Additionally, patients may report headache, watering of the eyes, ocular redness, and photophobia. If the scleritis is purely posterior there may be no redness.
When there is anterior scleritis, the redness is typically deeper in color or purpuric compared with the injected or “bloodshot” appearance of conjunctivitis or episcleritis. Typically, any congested vessels are deep and not mobile. Symptoms may vary depending upon the severity and type of scleritis that is present. Patients with suspected scleritis should be referred to an ophthalmologist for evaluation within a few days. Scleritis is often associated with systemic disease, including systemic rheumatologic and inflammatory disorders (table 4). (See "Clinical manifestations and diagnosis of scleritis".)
Benign conditions associated with red eye — The most common entities among the benign conditions that may be associated with a red eye are discussed anatomically from anterior to posterior (figure 1) in the following section and in the table (table 2).
Eyelid lesions — Hordeolum (stye) is an acute inflammation of the eyelid that presents as a localized painful and erythematous swelling or nodule. Chalazion is a painless localized eyelid nodule. Distinguishing characteristics are shown in the figure (figure 3) and discussed in detail separately. (See "Eyelid lesions", section on 'Hordeolum (stye)' and "Eyelid lesions", section on 'Chalazion'.)
Blepharitis — Blepharitis refers to inflammation of the eyelids. Patients generally present with chronic recurrent symptoms, which may vary over time, involving both eyes. Symptoms include pink eyes; red, swollen or itchy eyelids; gritty or burning sensation; excessive tearing; and crusted eyelashes. (See "Blepharitis".)
Conjunctivitis — Conjunctivitis refers to inflammation of the conjunctiva and is common in patients who present with a red eye. It is typically a benign and self-limited condition. Conjunctivitis can be categorized as infectious (predominantly viral or bacterial) or noninfectious (allergic, toxic, or noninfectious, noninflammatory).
Conjunctivitis is characterized by ocular discharge, engorgement of conjunctival blood vessels (“injection”), and various amounts of conjunctival edema (“chemosis”), and in viral or allergic cases may be associated with systemic symptoms. Findings that are not typical of conjunctivitis include headache or nausea, decreased visual acuity, ocular pain, fixed pupil, photophobia, decreased extraocular motility, severe foreign body sensation preventing spontaneous eye opening, ciliary flush, and corneal opacity. Such findings should prompt consideration of alternate diagnoses that might require ophthalmology referral. (See 'Serious conditions' above.)
Conjunctivitis is diagnosed in those with red eye and discharge only if the vision is normal (or unchanged), and there is no evidence of angle-closure glaucoma, keratitis, iritis, or scleritis. On examination, there should be no focal pathology in the lids such as hordeolum (stye), nodular ulceration or mass suspicious for neoplasia, or blepharitis (diffuse eyelid margin thickening and hyperemia with lash crusts). In these other disorders, conjunctival hyperemia, if present, is reactive rather than the primary symptom.
Conjunctivitis can be further categorized as:
●Infectious conjunctivitis, which is characterized by varying degrees and types of ocular discharge, may be associated with viral prodrome or contact with another person with red eye, or other systemic symptoms including fever or otitis media. The differentiation between viral and bacterial (picture 9) conjunctivitis, and management, is discussed in detail elsewhere. (See "Infectious conjunctivitis".)
●Allergic conjunctivitis (picture 10), which is characterized by prominent eye itching, watery discharge, as well as association with allergy symptoms such as nasal congestion or sneezing. (See "Allergic conjunctivitis: Clinical manifestations and diagnosis" and "Allergic conjunctivitis: Management".)
●Toxic conjunctivitis, which is characterized by reaction to direct damage to ocular tissues from a topically applied agent. It is most common in patients on long-term topical ocular medications, which may contain preservatives, such as those used to treat glaucoma. (See "Toxic conjunctivitis".)
Episcleritis — Episcleritis is a localized ocular redness from inflammation of episcleral vessels. It is most commonly unilateral and sectoral (picture 11), although it may also be nodular (picture 12). The vessels or nodules are typically quite distinct and are moveable over the scleral surface. Patients describe an achiness or awareness but typically do not report pain. Episodes typically last for a few weeks. Episcleritis can be recurrent and may be associated with underlying autoimmune disease. (See "Episcleritis".)
Episcleritis should be distinguished from scleritis, which can be sight-threatening, while episcleritis is not. (See 'Scleritis' above.) If the patient is presenting with the first episode of suspected episcleritis, or episodes recur frequently, referral to an ophthalmologist for confirmation of the diagnosis is appropriate. Symptoms of confirmed episcleritis may be managed with oral nonsteroidal antiinflammatory drugs (NSAIDs) by the primary care provider. Persistent symptoms may require other management by an ophthalmologist.
Subconjunctival hemorrhage — Patients with subconjunctival hemorrhage are generally asymptomatic. Typically, the patient is unaware of a problem until they look in the mirror or are informed of it by someone else. However, the appearance can be quite alarming to patients and others who interact with them. The clinical appearance of subconjunctival hemorrhage, with demarcated areas of extravasated blood just beneath the surface of the eye, is generally both obvious and diagnostic (picture 13). Subconjunctival hemorrhage may occur spontaneously or with Valsalva associated with coughing, sneezing, straining, or vomiting. The diagnosis is confirmed by normal acuity and the absence of discharge, photophobia, or foreign body sensation.
The blood is typically resorbed over one to two weeks, depending on the amount of extravasated blood. Because the subconjunctival space is loculated, the amount of blood may seem to increase on the second day, but this typically represents redistribution. No specific therapy is indicated. If subconjunctival hemorrhage is recurrent or if the patient has a history of bleeding disorder or blood dyscrasia, or is on anticoagulant therapy, evaluation of the anticoagulant therapy, or investigation as to whether there is an underlying hematologic or coagulation abnormality, is warranted. Eyes with subconjunctival hemorrhage in the setting of blunt trauma must be evaluated for the possibility of ruptured globe or other associated diagnoses. (See "Approach to diagnosis and initial treatment of eye injuries in the emergency department" and "Open globe injuries: Emergency evaluation and initial management".)
Contact lens complications — Contact lens use is common and may result in complications that vary from benign and self-resolving to potentially vision-threatening. Benign complications of contact lens use that may present with red eye can include problems related to dry eye, lens overwear (such as with extended wear overnight), and mechanical corneal abrasion. These complications are discussed in detail separately. (See "Complications of contact lenses".)
Corneal abrasions — Corneal abrasions (picture 14 and picture 15) are common and are caused by direct mechanical trauma to the surface of the eye, disrupting the corneal epithelium. Common mechanisms are from the infant’s finger or toenail while changing a diaper or from a branch while gardening. Corneal abrasions can also occur with contact lens use, from a foreign body under the lid, or after blunt trauma directly to the eye from a ball or fist. Patients may have a red eye and typically present with severe eye pain and a foreign body sensation. In some cases, there may be a retained foreign body under the lid or embedded in the cornea (picture 16). (See "Corneal abrasions and corneal foreign bodies: Clinical manifestations and diagnosis" and "Corneal abrasions and corneal foreign bodies: Management".)
Corneal abrasions should be carefully distinguished from bacterial keratitis in those who wear contact lenses. Patients with improper contact lens hygiene, use of contact lenses overnight, or extended wear lenses are at higher risk for bacterial keratitis, and we have a lower threshold for referring these patients for ophthalmology evaluation. (See 'Bacterial keratitis' above.)
Dry eye — Dry eye disease (picture 17 and picture 18) is a multifactorial disease of the ocular surface with loss of homeostasis of the tear film and ocular symptoms (eg, red eyes, irritation, dryness, paradoxical excessive tearing).
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Conjunctivitis (pink eye) (The Basics)" and "Patient education: Photokeratitis (arc eye) (The Basics)" and "Patient education: Subconjunctival hemorrhage (The Basics)")
●Beyond the Basics topics (See "Patient education: Conjunctivitis (pink eye) (Beyond the Basics)".)
SUMMARY AND RECOMMENDATIONS
●Overview – "Red eye" is a common presenting complaint in ambulatory practice. A small percentage of patients with red eye need urgent ophthalmological referral and treatment, but the vast majority can be treated by the primary care clinician. Conjunctivitis (allergic or viral) is probably the most common cause of red eye in the community setting.
●Patient evaluation – Patient history, measurement of visual acuity, and findings on penlight examination are important features in determining the cause and management of red eye (table 3). The history and eye exam provide guidance in deciding whether the patient requires in-person evaluation, and whether to refer the patient for ophthalmologic evaluation. The history should include whether vision is affected; whether there is pain, foreign body sensation, photophobia, double vision, or discharge; and whether there is a history of trauma or contact lens use. (See 'Determining who needs to be seen in person' above.)
Visual acuity of each eye should be assessed in all patients evaluated in-person using a Snellen chart or alternative means. Penlight examination should include pupil size and reactivity to light, the presence and nature of discharge, the pattern of redness, and the presence of corneal opacity, hypopyon, or hyphema. (See 'Determining severity and need for referral' above.)
●Causes and management – The differential diagnosis of the red eye includes serious conditions that require ophthalmologic evaluation (table 1) and benign conditions that may be managed by the primary care provider (table 2). (See 'Etiology and management' above.)
●Indications for emergency or urgent ophthalmic evaluation – In the patient with red eye, if vision is unaffected, the pupil reacts, there is no objective foreign body sensation or photophobia, and there is no corneal opacity, hyphema, or hypopyon, it is reasonable for the primary care clinician to manage the condition. The exception is in simple corneal abrasion, which may be associated with severe pain or decrease in vision, but is still reasonable for primary care clinicians to manage. (See 'Corneal abrasions' above.)
•The following are indications for emergency (same day) referral for ophthalmologic evaluation (table 1):
-Decreased vision, corneal opacity or infiltrate, especially in a contact lens wearer (see 'Bacterial keratitis' above)
-Red eye with hyphema or hypopyon (see 'Hyphema' above and 'Hypopyon' above)
-Unilateral red eye with headache, nausea, and vomiting, or severe eye pain (see 'Angle-closure glaucoma' above)
•The following are indications for urgent (within one to two days) referral (table 1):
-Red eye with photophobia, foreign body sensation, or watery discharge; associated with history of viral infection, or rash in the trigeminal distribution (see 'Viral keratitis' above)
-Aching, dull pain associated with photophobia (see 'Iritis (anterior uveitis)' above and 'Scleritis' above)
●Benign conditions associated with red eye – There are many benign conditions that may be associated with a red eye. Conjunctivitis (allergic or viral) is probably the most common cause of red eye in the community setting. (See 'Benign conditions associated with red eye' above.)
Conjunctivitis is characterized by ocular discharge, engorgement of conjunctival blood vessels (“injection”), and various amounts of conjunctival edema (“chemosis”), and in viral or allergic cases may be associated with systemic symptoms. Findings that are not typical of conjunctivitis include headache or nausea, decreased visual acuity, ocular pain, fixed pupil, photophobia, decreased extraocular motility, severe foreign body sensation preventing spontaneous eye opening, ciliary flush, and corneal opacity.
