What Causes Red Eyes?

Patient Presentation

A 15 year-old female came to clinic with a 2 day history of increased redness in her left eye. The patient states that she has been having bilateral eye redness and discharge for 1 month and was prescribed Patanol® which has helped with some itchiness. For 2 days she has had consistent blurry vision, tearing, photophobia, and mild pain. She also began to have some headache and slight sore throat 1 day ago. She normally wears contact lenses and glasses and has been using the same contact lens cleaner. She denied any trauma. The past medical history showed she is taking cetirizine for seasonal allergic rhinitis. The family history is positive for glaucoma. Previously her eye pressures were normal. The review of systems is negative for fever, rashes, joint pain or swelling, weight changes or other headaches.

The pertinent physical exam revealed normal vital signs including a blood pressure of 90/70. Her visual acuity was grossly normal. Increased clear tearing was noted. Her sclera and palpebral conjunctiva were reddened with increased vasculature particularly around the cornea. There were small bubbles/spots scattered across the cornea with the left side more affected than the right. The retinal examination was grossly normal but suboptimal because of photophobia. No lid or facial skin changes were noted. The diagnosis of probable keratitis was made. The pediatrician contacted the ophthalmologist who wanted to see the patient as soon as possible as keratitis is a potentially vision-threatening condition. Additionally, other problems such as glaucoma could not be excluded. The ophthalmologist’s examination showed visual acuity of 20/30 bilaterally with scattered infiltrates of the cornea L > R, and confirmed epidemic keratoconjunctivitis of viral etiology. Lubricates and oral analgesics were prescribed.

Epidemic keratoconjunctivitis is an acute viral disease usually caused by adenovirus types 8, 19, and 37, but also other viruses such as echoviruses. The virus is spread by contaminated secretions directly or indirectly between humans with an incubation period of 4-10 days. It can be transmitted from symptom onset to 12 days later. It is usually associated with decreased visual acuity, watery discharge, pain, photophobia and erythema of the conjunctiva. It can occur unilaterally or bilaterally. Systemic complaints can also occur such as low grade fever, headache, lymphadenopathy and fatigue. Subcorneal infiltrates develop and may persist for up to 2 years and can cause permanent scarring.

Learning Point
Usually the common causes of red eyes can be managed by a primary care physician. If a complete evaluation cannot be done, or if the red eye is thought to be part of a more serious underlying disease process then prompt referral should be made. Additionally, acute iritis, glaucoma, keratitis, scleritis and hyperacute bacterial conjunctivitis should also be referred. Normal acute and chronic conjunctivitis can usually be managed by a primary care physician.

The differential diagnosis for a red eye includes:

  • Anatomic
    • Nasolacrimal duct obstruction
    • Congenital or acquired glaucoma
  • Inflammation
    • Conjunctivitis – allergic, bacterial, viral, possibly fungal
    • Dacrocystitis
    • Iritis
    • Cellulitis – periorbital and orbital
    • Keratitis
  • Trauma
    • Corneal abrasion
    • Dry eye irritation
    • Foreign body – including contact lenses
    • Blunt trauma including rubbing, subconjunctival hemorrhage
    • Penetrating trauma
    • Chemical exposure
  • Systemic illness
    • Ataxia-telangectasia
    • Connective tissue disease
    • DRESS syndrome
    • Herpes simplex
    • Kawasaki disease
    • Leukemia
    • Lyme disease
    • Measles
    • Stevens-Johnson syndrome
    • Varicella

Questions for Further Discussion
1. What is the most common cause of hyperacute bacterial conjunctivitis?
2. What organism has been associated with contact lens solution contamination causing keratitis?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.
To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Information prescriptions for patients can be found at MedlinePlus for these topics: Eye Diseases and Eye Infections.

Glover G. Infections of the eye. In Pediatrics a Primary Care Approach, Berkowitz CD, edit. W. B Saunders Co. Philadelphia, PA. 1996;200-201.

Schachat AP. The Red Eye. In Principles of Ambulatory Medicine. Williams and Wilkins. 1998;1488-1491.

Viney KA, Kehoe PJ, Doyle B, Sheppeard V, Roberts-Witteveen AR, Semirli H, McPhie KA, Dwyer DE, McAnulty JM. An outbreak of epidemic keratoconjunctivitis in a regional ophthalmology clinic in New South Wales. Epidemiol Infect. 2008 Sep;136(9):1197-206.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Interpersonal and Communication Skills
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.


    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital