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A 41-year-old woman presents to your clinic complaining of a “red eye.” The redness is diffuse and has been present for 2 days. She also reports mild, watery discharge and a slight sensation of grittiness. She does not have significant pain and has not noticed any change in her vision.

  • What focused questions can you ask to narrow your diagnostic considerations?
  • What alarm symptoms should prompt immediate referral to an ophthalmologist?
  • How would you discern whether her eye complaints signify ocular involvement from a systemic disease?

Ophthalmologic complaints are very common in clinical practice, accounting for approximately 3% of emergency department visits.1 Frequently, patients report a “red eye,” which generates a broad range of diagnostic possibilities. Most causes of a “red eye” are benign or self-limited and can be managed by a primary care physician. However, some etiologies require urgent referral to an ophthalmologist. While the physical examination is important, a good history is critical in separating the benign causes of a “red eye” from those associated with increased morbidity. See Figure 16–1 for an illustration of the structures of the orbit and eyelid.

Figure 16–1

Structures of the orbit and eyelid. (Illustration by Richard Wong.)

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ConjunctivaA thin outer membrane lining the inner lids (palpebral conjunctiva) and the globe (bulbar conjunctiva)
Meibomian glandA modified sweat gland in the tarsal plate of the eyelid
Ciliary bodyPart of the eye involved in production of aqueous humor and in accommodation, located between the iris and the choroid
ChoroidA vascular layer in the eye between the sclera and retina
ChemosisEdema of the conjunctiva
Orbital septumAlso known as the palpebral ligament; serves as the anterior boundary of the orbit
Foreign body sensationThe feeling that something is “stuck” in the eye
Seronegative spondyloarthropathiesReactive arthritis, psoriatic arthritis, inflammatory bowel disease, ankylosing spondylitis

The erythema in a “red eye” is often caused by conjunctival inflammation but also may result from dilated scleral or episcleral vessels or inflammation of the deeper structures of the eye and surrounding tissues. Although the exact incidence of diagnoses presenting as a “red eye” is not well defined, most are benign. In the emergency department, 75% of ophthalmologic complaints are due to conjunctivitis, corneal abrasions, or foreign bodies.1 In a study of patients presenting to an outpatient clinic with eye symptoms, the most common diagnoses were conjunctivitis and benign disorders of the eyelid such as blepharitis. In the same study, morbid diseases were rare; acute angle-closure glaucoma composed only 1.2% of diagnoses and uveitis composed only 0.6%.2

Differential Diagnosis

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Explanation1,3–5Prevalence per 1000 Population (ages 1–74)a,6
Ocular diagnoses that do not require ophthalmology referral
ChalazionChronic granulomatous ...

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