INTRODUCTION — "Red eye" is a common presenting complaint in ambulatory practice. This topic presents an approach for distinguishing patients with red eye who must be referred to an ophthalmologist, such as those with angle-closure glaucoma, from patients who can be managed by the primary care clinician, such as those with allergic conjunctivitis (table 1 and table 2). Some distinguishing features of conditions presenting as a red eye are summarized in a table (table 3).
The specific diagnosis and treatment of many of these disorders are discussed separately. (See "Eyelid lesions" and "Conjunctivitis" and "Corneal abrasions and corneal foreign bodies: Clinical manifestations and diagnosis" and "Uveitis: Etiology, clinical manifestations, and diagnosis" and "Angle-closure glaucoma" and "Photokeratitis" and "Blepharitis" and "Conjunctival injury", section on 'Subconjunctival hemorrhage'.)
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, although the vast majority can be treated by the primary care clinician. There are little epidemiologic data on the red eye, and there are no evidence-based data to guide us in 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].
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. The history and ocular examination provide guidance in the decision about 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 to be seen by a clinician. Certain historical features or presenting complaints signal the need for clinician examination and possibly patient referral. The following questions should be asked in all patients. Many cases can be handled by primary care providers by telephone or telemedicine (video) or by having the patient send phone images.
The coronavirus disease 2019 (COVID-19) pandemic has produced reports on approach to telemedicine for the red eye . There are critical questions that determine if in-person evaluation or referral to an ophthalmologist are warranted. There is emerging evidence that virtual consultation for red eye results in accurate diagnosis and can result in decreased need for in-person visits .
If the answer to any of the following questions below is yes, there is more likely to be a sight-threatening process and in-person evaluation or referral to an ophthalmologist is warranted:
●Is 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?
●Is there foreign body sensation? – Does it feel as though there is something in your eye, interfering with your ability to keep your eye open? A foreign body sensation is the cardinal symptom of an active 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; with the exception of the initial presentation for corneal abrasion or foreign body, such patients warrant emergency or urgent referral to an ophthalmologist. By comparison, many patients report a "scratchy feeling," "grittiness," or a sensation "like sand in my eyes" with allergy, viral conjunctivitis, or dry eyes. This is subjective foreign body sensation and does not necessarily suggest a corneal problem that requires referral.
●Is there photophobia? – Are you sensitive to bright light? Patients with photophobia should always be examined by a clinician.
Patients with an active corneal process have objective signs of photophobia as well as objective signs of foreign body sensation. They 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. Patients with iritis have objective signs of photophobia but no objective foreign body sensation.
●Was there recent trauma, eye surgery, or contact lens wear? – A history of contact lens wear in the setting of discharge and a red eye should increase the suspicion of keratitis . (See "Complications of contact lenses", section on 'Infectious keratitis'.)
●Is there new onset of binocular double vision?
Determining severity of condition
General observation — Further history and general observation of 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, simple patient observation can provide reliable clues.
●Is there discharge, other than tears, that continues throughout the day? – Morning crusting followed by a watery discharge for the remainder of the day is characteristic of many self-limited processes such as allergy, stye or hordeolum, viral conjunctivitis, allergic conjunctivitis, and dry eyes. Patients typically interpret morning crusting as "pus."
●Bacterial conjunctivitis and bacterial keratitis cause opaque discharge that persists throughout the day and requires specific therapy. Bacterial conjunctivitis, which is typically not associated with a reduction in visual acuity, foreign body sensation, or photophobia, may be treated by the primary care clinician. Bacterial keratitis, on the other hand, which may or may not affect vision but typically causes objective foreign body sensation and photophobia, requires emergency referral. (See 'Bacterial keratitis' below.)
●Lid and conjunctival entities do not cause objective foreign body sensation or photophobia. The patient will be 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.
●By comparison, the patient suffering from infectious keratitis, iritis, or angle-closure glaucoma is likely to have objective signs indicating the more serious nature of the problem. These entities all require ophthalmologic consultation. Signs of these entities include corneal whitening or opacity, eyeball tenderness on palpation, and ciliary flush, which is redness localized to the limbus (the transition zone between cornea and sclera).
●Measurement – Vision should be documented for every patient who is seen for an eye complaint. (An inquiry should be made about a change in vision on every telephone triage.) Each eye should be tested separately. Snellen acuity is the standard; however, this test requires using a Snellen chart at 20 feet with best correction or pinhole and is often difficult to perform.
An alternative in a triage setting is measurement of near vision. Allow the patient to use his or her 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. This measurement should be made before lights are shined in the eye or drops of any sort are applied.
●Importance of results – In cases in which a lid disorder, conjunctival process, corneal abrasion, or foreign body is suspected, the presence of normal acuity can be a source of reassurance to the primary care clinician that it is reasonable for them to initiate therapy. On the other hand, if acuity is reduced in the presence of a red eye beyond that which the patient reports is typical, the clinician should suspect one of the more worrisome diagnoses: infectious keratitis, iritis, or angle-closure glaucoma. These patients should be referred for initial therapy.
Penlight examination — The penlight 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) in size? – The pupil is pinpoint in cases of corneal abrasion, infectious keratitis, or iritis. 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. Abrasions are usually caused by focal trauma to the surface of the eye. Traumatic iritis may occur after blunt trauma, a softball, or a fist, but there are no corneal findings.
●Is there purulent discharge? – Purulent discharge suggests bacterial conjunctivitis or bacterial keratitis. In conjunctivitis, there are no opacities by penlight or staining defects with fluorescein.
●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 (eg, dry eye syndrome). In these entities, the entire mucus membrane is equally involved. By comparison, ciliary flush is characteristic of the 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.
●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 the aid of fluorescein. Fluorescein is 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 cells in the anterior chamber, or hyphema, a layer of red 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 significant 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".)
No role for fundus examination — The fundus examination is typically not helpful in the differential diagnosis of the red eye. In the benign entities such as lid and conjunctival processes, the fundus examination is easily performed and has no associated pathologic features. In iritis and keratitis, the pupil will be very small and the patient 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 because of increasing corneal edema from high intraocular pressure. A fundus examination is important if there is red eye in the presence of swelling or vesicular eruption respecting the midline of face, proptosis, or nonreactive pupil to characterize optic nerve involvement.
ETIOLOGY AND MANAGEMENT — The differential diagnosis of the red eye includes benign conditions (table 2) and serious conditions that require ophthalmologic evaluation (table 1). Features that can help distinguish these include history, visual acuity, sensation of a foreign body, photophobia, discharge, pupil size and reactivity, pruritus or pain, and fluorescein staining (table 3). Photographs of specific conditions show typical features of blepharitis (picture 5 and picture 6), episcleritis (picture 7 and picture 8), bacterial conjunctivitis (picture 9), allergic conjunctivitis (picture 10), corneal abrasion (picture 11), corneal foreign body (picture 12), anterior uveitis (picture 13), hyphema (picture 4), hypopyon (picture 14 and picture 3), bacterial keratitis endophthalmitis (picture 15), angle-closure glaucoma (picture 1), and subconjunctival hemorrhage (picture 16).
In the section to follow, the conditions that require emergency (same day), or urgent (within two to three days) ophthalmologic evaluation are summarized (table 1).
Common benign conditions — The most common entities among the benign conditions are listed below and in the table (table 2).
Blepharitis — Blepharitis is discussed in detail elsewhere. (See "Blepharitis".)
Conjunctivitis — Conjunctivitis is discussed in detail elsewhere. (See "Conjunctivitis" and "Allergic conjunctivitis: Clinical manifestations and diagnosis" and "Allergic conjunctivitis: Management".)
Corneal abrasions — Corneal abrasion or foreign bodies are discussed in detail elsewhere. (See "Corneal abrasions and corneal foreign bodies: Clinical manifestations and diagnosis".)
Contact lens overwear — Contact lens overwear is discussed elsewhere. (See "Complications of contact lenses".)
Dry eye syndrome — Dry eye syndrome is discussed elsewhere. (See "Dry eye disease".)
Episcleritis — Episcleritis is a localized ocular redness from inflammation of episcleral vessels. It is most commonly unilateral and sectoral, although it may also be nodular. The vessels or nodules are typically quite distinct and are moveable over the scleral surface. Patients describe an achiness or awareness but typically don’t report pain. Episodes typically last for a few weeks. Episcleritis can be recurrent and may be associated with underlying autoimmune disease. Episcleritis is not sight-limiting or sight-threatening; symptoms are typically managed with oral nonsteroidal antiinflammatory drugs (NSAIDs) by the primary care provider, although confirmation of diagnosis by an eye care provider at first episode or for frequent recurrence may be reassuring to both patient and primary care provider.
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. 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 16). However, the appearance can be quite alarming to patients and others who interact with them. 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, referral to a primary care provider for 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 retrobulbar hemorrhage. (See "Conjunctival injury", section on 'Subconjunctival hemorrhage'.)
More serious conditions
Angle-closure glaucoma — Acute angle-closure glaucoma is relatively uncommon, but the incidence increases dramatically with age . Angle closure leads to increased intraocular pressure (figure 2A-B). The patient with angle-closure glaucoma typically appears to be in general distress. They are likely to be slumped over, covering the eye or clutching the frontal or temporal region of the head with one hand, and complaining of 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 complain of "the worst headache in my life" and do not attribute their symptoms to the eye. (See "Angle-closure glaucoma".)
Unnecessary neurologic workup and imaging that may critically delay treatment can be avoided if the red eye is noted and assessed. Acuity becomes increasingly reduced as the duration of the attack increases. These patients may be photophobic. They do not typically complain of a 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).
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.
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.
Hyphema — Hyphema refers to the finding of red blood cells layered out in the anterior chamber. 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 out in the anterior chamber. This finding warrants same-day evaluation by an ophthalmologist as it can be associated with infectious keratitis or endophthalmitis. (See "Bacterial endophthalmitis".)
Iritis — Inflammation of the anterior uveal tract is called iritis or 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 in a similar fashion to those with an active corneal process, but there is no foreign body sensation per se. 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 an active corneal process and 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. 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 within a matter of 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 will require extensive evaluation for etiology.
Infectious keratitis — Infectious keratitis can be caused by bacteria, viruses, fungi, or parasites . 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 . (See "Complications of contact lenses", section on 'Infectious keratitis'.)
Bacterial keratitis — Bacterial infectious keratitis warrants evaluation by an ophthalmologist on the same day. The patient will complain of foreign body sensation and have trouble keeping the involved eye open, a sign of an active corneal process. Bacterial pathogens include Staphylococcus aureus, Pseudomonas aeruginosa, coagulase-negative Staphylococcus, diphtheroids, Streptococcus pneumoniae, and polymicrobial isolates .
Improper contact lens wear is the largest risk factor for bacterial keratitis . Overnight wear of contact lenses is associated with a higher incidence of bacterial keratitis, but the entity can 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 ocular surfaces, topical corticosteroid use, and immunosuppression, can predispose to bacterial keratitis.
The diagnostic finding in bacterial keratitis is a corneal opacity or infiltrate (typically a round white spot) in association with red eye, photophobia, and foreign body sensation. This infiltrate or ulcer (>0.5 mm in size) can be seen with a penlight and does not 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).
Treatment requires urgent ophthalmological referral and prompt initiation of topical bactericidal antibiotics (ideally after obtaining cultures). These antibiotics are sometimes compounded in fortified concentrations, 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 [9-12].(See "Complications of contact lenses", section on 'Infectious keratitis'.)
Viral keratitis — Herpes simplex causes infectious keratitis, characterized by red eye, photophobia, foreign body sensation, and watery discharge. There may be a faint branching grey opacity on penlight examination (picture 17). 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. (See "Herpes simplex keratitis".)
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.
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 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".)
Scleritis — Scleritis is a painful, destructive, and potentially blinding disorder that may also involve the cornea, adjacent episclera, and underlying uveal tract. Scleritis has a striking, highly symptomatic clinical presentation (picture 18). Scleritis is usually characterized by severe, 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 when 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".)
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)".)
●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. (See 'Overview' above.)
●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 ocular examination provide guidance in the decision about whether to refer the patient for ophthalmologic evaluation. The history should include whether vision is affected, whether there is a foreign body sensation, whether there is photophobia, whether there is a history of trauma or contact lens use, and whether discharge is present. Visual acuity of each eye should be assessed in all patients 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 'Patient evaluation' above.)
●Causes and management – The differential diagnosis of the red eye includes benign conditions (table 2) and serious conditions that require ophthalmologic evaluation (table 1). (See 'Etiology and management' above.)
●Indications for emergency 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 following are indications for emergency referral for ophthalmologic evaluation (table 1):
•Unilateral red eye with pain, nausea, and vomiting (see 'Angle-closure glaucoma' above)
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