Clinical Presentation
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.
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 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.
●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 [5]. (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).
Ophthalmologic examination
Visual acuity
●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.