Red eye for the internist: When to treat, when to refer

We review the conditions that can cause this ocular sign—the ones that internists can comfortably manage, and the ones that are best managed by an eye specialist.

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When a patient presents with redness in the eye, the cause needs to be diagnosed quickly. Some of the diseases that cause redness in the eye can be initially managed by an internist, but others call for quick referral to an ophthalmologist. This article reviews the spectrum of conditions manifesting as a red eye, emphasizing how to differentiate between the benign and the vision-threatening.


  • Blepharitis, conjunctivitis, corneal abrasion, dry eye, and subconjunctival hemorrhage are benign and can usually be managed initially by an internist, although referral is usually indicated if symptoms persist or progress.
  • Patients with corneal bacterial infection, uveitis, scleritis, or acute narrow-angle glaucoma need immediate referral to an ophthalmologist, as do most patients with a red eye who use contact lenses, who have had trauma to the eye, or who have vision changes, severe pain, nausea, vomiting, severe headache, marked purulent discharge, or abnormalities in the cornea or anterior segment.
  • Because it is difficult to distinguish between infectious and noninfectious conditions, and because treating infections with corticosteroids alone can have grave consequences, we recommend that internists generally not use topical corticosteroids to treat eye symptoms.



MANY PATIENTS present to internists because of redness in the eye. The possible causes range from benign (which generally can be handled by an internist) to vision-threatening (which need prompt or emergency referral to an ophthalmologist).

This article, a primer on red eye for the internist, reviews the conditions that can cause this ocular sign—the ones that internists can comfortably manage and the ones that are best managed by an eye specialist (TABLE 1).


The internist should ascertain:

  • Whether one or both eyes are affected
  • The duration of symptoms
  • Previous eye and medical problems
  • The type of discharge (watery or purulent), if present
  • Whether the patient has any visual changes, pain, or photosensitivity.

Refer patients to an ophthalmologist for further evaluation if they use contact lenses or if they have had trauma to the eye, vision changes, severe pain, or systemic symptoms such as nausea, vomiting, or severe headache.



  • Visual acuity
  • Pupil size and reaction to light
  • The pattern and location of the redness
  • The cornea and anterior segment for gross abnormalities such as corneal opacities, hypopyon (a layer of inflammatory cells in the anterior chamber), and hyphema (hemorrhage in the anterior chamber) (Use a penlight.)
  • The preauricular lymph nodes. Preauricular lymphadenopathy, detected by palpation, suggests but is not specific for viral conjunctivitis.
  • Funduscopy has little value in evaluating a red eye.

Refer immediately anyone who has marked purulent discharge or abnormalities in the cornea or anterior segment.

FIGURE 1. Subconjunctival hemorrhage after blunt trauma to the periocular area.


Subconjunctival hemorrhage

Broken conjunctival blood vessels can bleed into the subconjunctival space (FIGURE 1). These hemorrhages can occur spontaneously or be due to trauma, the Valsalva maneuver, antiplatelet agents, antithrombotics, or vitamin E in high doses.

Subconjunctival hemorrhages are harmless and do not cause pain or vision changes. No treatment is required, and the blood resorbs within a few weeks. However:

  • Measure the blood pressure—uncontrolled hypertension can present with subconjunctival hemorrhage.1
  • If the patient is on an antithrombotic agent, test the prothrombin and activated partial thromboplastin times.
  • If the patient has recurrent unexplained episodes of subconjunctival hemorrhage, look for a bleeding disorder such as von Willebrand disease, hemophilia, or autoimmune thrombocytopenic purpura.


Blepharitis, a common condition, is inflammation of the eyelid margins. Anterior blepharitis affects the eyelashes and anterior eyelid margin and is most often caused by a low-grade staphylococcal infection or seborrheic dermatitis. Posterior blepharitis involves the orifices of the slender sebaceous glands of the eyelids (the meibomian glands) and is often associated with acne rosacea.

Symptoms include ocular burning, a sensation that a foreign body is in the eye, and watering. Symptoms are typically worse in the morning and gradually improve throughout the day. Although the onset is sudden in some patients, blepharitis is usually chronic—often lifelong—and starts insidiously.

A sign of anterior blepharitis is crusting around the eyelashes. Patients with concomitant seborrheic dermatitis also have oily skin and flaking from the eyebrows and scalp. Signs of posterior blepharitis are oil inspissation around the meibomian gland openings, telangiectasias of the eyelid margin, and accompanying acne rosacea (skin pustules, telangiectasias, and erythema).

Treat both forms with eyelid hygiene: applying warm compresses to the eyelid margins, followed by gentle massage to remove the debris from the eyelashes and meibomian glands. This is done two to four times daily until acute symptoms resolve, then once daily. Because blepharitis is chronic, eyelid hygiene must be continued indefinitely to prevent acute exacerbations.

Posterior blepharitis that does not respond to hygiene can be also treated with oral tetracycline, which is believed to improve meibomian gland function and alter bacterial colonization.

Some patients also have tear deficiency, which can be addressed with tear replacement therapy (see below).2,3

Keratoconjunctivitis sicca (dry eye)

Dryness can cause mild eye redness. Patients typically report a foreign body sensation, burning, and paradoxically, watering. Symptoms often worsen as the day progresses and are most prominent at night.

Dryness can be due to:

  • Local disturbances in the tear film such as aqueous deficiency
  • An abnormal eyelid position
  • Systemic autoimmune conditions such as Sjögren syndrome
  • Hormonal changes (eg, in menopause)
  • Excessively dry environments (eg, winter)
  • Medications, including anticholinergics, antihistamines, antidepressants (eg, tricyclics), and antihypertensives (eg, beta-blockers).

Staining the cornea with fluorescein highlights small epithelial defects; rose bengal highlights devitalized cells.

Treat initially with artificial tears (eg, Refresh Tears, GenTeal, Systane, Bion Tears) and ointments (eg, Refresh Liquigel, Lacri-Lube). Dry eye has an inflammatory component; cyclosporine ophthalmic 0.05% (Restasis) may increase tear production and improve symptoms.4

Refer patients with symptoms that do not respond to therapy. An ophthalmologist can place silicone plugs in the canaliculi, a procedure with a 75% success rate for improving dry-eye symptoms.5 Plugs must be carefully fitted: loose ones can spontaneously dislodge, and tight ones can irritate the eye.

Eyelid malposition

Entropion (in-turning of the eyelid) causes eyelashes to rub on the cornea. Ectropion (outward turning of the eyelid) results in tear-film abnormalities and corneal exposure. Both conditions are most commonly caused by aging but may be secondary to scarring or to mechanical, paralytic, or congenital conditions. Definitive treatment involves surgery to restore the normal eyelid position. Several techniques have high success rates.1

Lagophthalmos (inability to fully close the eyes) is caused by orbicularis muscle dysfunction, which may be secondary to Bell palsy, stroke, or neurosurgical procedures that disrupt the facial nerve. The exposed cornea is prone to dryness and irritation. Treatments include artificial tears, lubricating ointments, and surgery—gold weight placement or suturing the eyelid margins (tarsorrhaphy).

Floppy eyelid syndrome refers to a lax upper eyelid that may evert during contact with the pillow during sleep, resulting in irritation and inflammation of the upper palpebral conjunctiva. Signs and symptoms are unilateral eye irritation, burning, and a ropy mucous discharge, which is usually worse in the morning. The upper eyelid is lax and easily everted when pulled toward the eyebrow. Most patients are obese, have obstructive sleep apnea, and sleep on the affected side.

Tell the patient to tape the affected eyelid shut or wear a protective eye shield in bed to prevent rubbing the eye on the pillow. Definitive treatment is surgery to tighten the lax upper eyelid.6


Conjunctivitis involves hyperemia and edema of the bulbar conjunctiva (the part of the conjunctiva covering the eyeball) along with papillary and follicular changes of the palpebral conjunctiva (the inner layer of the eyelids).

Conjunctivitis can be viral, bacterial, or allergic, or due to wearing contact lenses; the cause can usually be distinguished by the history and physical examination.

FIGURE 2. Viral conjunctivitis with an intensely red eye and a white fibrin membrane in the inferior fornix.

Viral conjunctivitis, usually caused by an adenovirus, is more common than bacterial conjunctivitis in adults. The patient typically has had a recent upper respiratory tract infection or was exposed to conjunctivitis.

The onset is acute with redness in one eye and excessive watery discharge (FIGURE 2). The other eye becomes involved within days in about half of cases. Symptoms can include itching, photophobia, watering, and foreign body sensation. Patients often report “matting” and “crusting” of the eyelids in the mornings. Examination reveals follicular conjunctivitis on the lower palpebral conjunctiva and often preauricular lymphadenopathy.

Treat supportively with cool compresses. Symptoms often worsen for a few days, then slowly improve over 1 to 2 weeks.

Viral conjunctivitis is contagious for 2 weeks after the second eye becomes involved, and good hygiene must be maintained to avoid spreading it to coworkers and family members. Those who work with the public, in schools, or in health-care facilities should be given a 2-week leave of absence to avoid spreading the infection to others.

Refer to an ophthalmologist if symptoms do not resolve in 2 weeks, as certain subtypes of adenovirus can cause prolonged symptoms with corneal involvement.7

FIGURE 3. Bacterial conjunctivitis. Note pus
in inferior fornix and along eyelid margins.
FIGURE 4. Hyperacute conjunctivitis caused by
Neisseria gonorrhoeae. Note profuse discharge in
a very red eye.

Bacterial conjunctivitis can be caused by gram-positive or gram-negative organisms and is differentiated from viral conjunctivitis by thick, purulent discharge rather than excessive watering (FIGURE 3). Examination reveals papillary conjunctivitis and sometimes preauricular lymphadenopathy.

Treat bacterial conjunctivitis empirically with antibiotic eyedrops (eg, a fluoroquinolone, a polymyxin, or sulfacetamide—several brands available) four times daily for 7 to 10 days, even though most cases are self-limited and do not result in complications. Cultures can be obtained, especially if the patient is in the hospital8 or if the conjunctivitis persists after 1 week of antibiotic therapy.

Refer patients with vision changes or who do not improve after 1 week of treatment.9,10

Hyperacute bacterial conjunctivitis should be suspected if the onset is abrupt with copious purulent discharge. Most often associated with Neisserria gonorrhoeae infection, it can lead to corneal involvement, including perforation and visual loss (FIGURE 4).

Treat aggressively with both a topical antibiotic (usually a fluoroquinolone) four times daily and a systemic antibiotic such as ceftriaxone (Rocephin) given as a single 1-g intramuscular injection.11,12 Because one-third of patients with gonorrheal infection also have chlamydial infection, treatment for both diseases is frequently prescribed.

Chlamydial infection, a sexually transmitted disease, can cause chronic follicular conjunctivitis. The genital tract infection may be asymptomatic. Diagnosis is made by swabbing the conjunctiva to culture for Chlamydia trachomatis. Treat systemically with either azithromycin (Zithromax) in a single 1-g oral dose or a 10–14-day course of either doxycycline (Doryx) 100 mg twice daily or erythromycin 250 mg four times daily.13

Allergic conjunctivitis is characterized by bilateral itching that worsens with scratching. Discharge is variable but is usually clear or white and stringy. Many patients have a history of seasonal or perennial allergies.

Remove offending allergens, if possible. Topical mast cell stabilizers and antihistamines relieve symptoms but may exacerbate underlying dry eye symptoms. A combined mast cell stabilizer and antihistamine such as olopatadine (Patanol), ketotifen (Zaditor), or epinastine (Elestat) can be given twice daily.14,15 Artificial tears can treat the associated dryness.

Topical corticosteroids may be used to treat an acute, severe episode but should not be used long-term. In fact, because it is difficult to differentiate between infectious and noninfectious eye conditions, and because treating some infections with corticosteroids by themselves can have grave consequences, we recommend that internists generally refrain from using them.

Oral antihistamines may relieve symptoms but are usually less effective than topical therapy.

Refer if symptoms do not resolve after 2 weeks of topical treatment.

Giant papillary conjunctivitis, most often seen in patients who wear soft contact lenses, presents with bilateral contact lens intolerance, itching, mucous discharge, and giant papillae on the upper palpebral conjunctiva.

Again, promptly refer any patient who wears contact lenses and presents with a red eye, owing to the risk of a vision-threatening corneal infection. The patient should stop wearing contact lenses for about 1 month, after which he or she can be refitted with new soft or gas-permeable lenses and taught better lens hygiene. During an acute episode, topical mast cell stabilizers are helpful for mild irritation, and topical steroids (prednisolone phosphate 1%) are helpful for more severe irritation. Topical steroids should never be used on a long-term basis because of possible adverse effects. Artificial tears can be used for dryness.15

FIGURE 5. Corneal abrasion staining brilliantly with fluorescein dye under a cobalt blue filter.

Corneal abrasion

Corneal abrasions (traumatic removal of part of the corneal epithelium) are often caused by fingernails, paper, makeup applicators, metallic foreign bodies, or vegetative matter. Signs and symptoms are pain, photophobia, foreign body sensation, and watering. Depending on the location and severity of the abrasion, visual acuity may be decreased. To see abrasions better, instill fluorescein dye and examine the eye under a light with a cobalt blue filter or under Wood’s lamp illumination (FIGURE 5).

Treat with topical antibiotics to prevent infection until the corneal epithelium has healed.16 However, most abrasions heal rapidly without sequelae because epithelial cells proliferate and migrate rapidly.

Refer if symptoms persist for longer than 48 hours or if pain suddenly worsens after the healing process has started.

Pingueculae and pterygia

A pinguecula is a small, yellow, benign growth on the nasal and temporal conjunctiva near the limbus. A pterygium is a wing-shaped band of fibrovascular tissue originating on the conjunctiva and extending onto the cornea. Both conditions are idiopathic but are believed to arise from chronic sun exposure.

Pingueculae can become inflamed and can cause eye redness and irritation. Treat conservatively with lubrication and judicious use of topical steroids; if irritation persists, pingueculae can be surgically removed.17

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