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KEY POINTS
■ Manifestation as a unilateral red eye with pain suggests that the patient could have a sight-threatening condition. The three most likely diagnoses associated with this clinical presentation are chronic open-angle glaucoma (COAG), acute angle-closure glaucoma (AACG), and iritis.
■ The key features to consider when examining the eye are visual acuity, pain, the area of injection, the cornea, and the pupil. The next most useful finding is intraocular pressure measurement.
■ Treatment of glaucoma and iritis are completely opposite from each other. Acute angle-closure glaucoma is treated by constricting the pupil with pilocarpine eye drops, which draws the iris out of the angle of the eye. Pupil dilation is fundamental to the treatment of iritis.
■ Verifying that the IOP is not elevated and that the anterior chamber is not shallow before dilating the pupil is essential. Where the equipment and expertise are not available for either IOP measurement or dilation, referral to an eye specialist is indicated as these procedures can result in serious damage to the eye when performed by an inexperienced clinician.
The acute red eye is a challenge to diagnose and manage because this common manifestation has a wide variety of possible causes. For many primary care clinicians, the differential diagnosis is confusing and leads to unnecessary referrals or failure to recognize serious pathology. The keys to an accurate clinical diagnosis of the acute red eye, as with most other diseases of the body, are to perceptively elicit a history, make accurate physical observations, and pay careful attention to the profile of the patient in front of you.
This article will not discuss all causes or treatment options for the acute red eye; rather it focuses on ciliary injection, or redness, observed near the limbus. The corneal limbus is the line of demarcation where the clear corneal tissue turns into white scleral tissue. Redness of the conjunctiva and sclera that immediately surround the cornea (or limbus) in a unilateral red eye needs to be recognized and managed appropriately. The clinical presentation is a diagnostic dilemma for many primary care and emergency/urgent care clinicians, who may easily make a wrong diagnosis and initiate the incorrect treatment if important clinical findings are overlooked.
CASE
Mrs. B., a 32-year-old female, presented to the clinic with a unilateral, moderately painful, red right eye. Onset of mild tenderness was 2 days ago, and redness gradually developed with increasing deep aching pain that the patient described as a 3 on a 10-point scale (0, no pain; 10, unbearable pain). The only discharge was mild tearing. The patient's medical history was negative for eye problems, and she had no history of trauma. The patient denied chronic medical problems. Her family history was negative for any significant eye problems except that in later years her grandparents had a history of cataracts. No other family members at home were complaining of similar symptoms.
Physical examination Mrs. B. appeared to be healthy and in no apparent distress. She was afebrile with lungs clear to auscultation and had a regular heart rate and rhythm. She had dark hair, brown eyes, and a dark complexion. Her visual acuity was 20/70 OD (the right eye) and 20/20 OS (the left eye). The patient's eyelids were bilaterally symmetrical and not swollen. Her extraocular movements were intact. Ciliary injection around a clear cornea was noted in the patient's right eye. The anterior chamber appeared deep bilaterally without increased iris shadow. Her pupils were round and reacted to light bilaterally; the pupil of the left eye was slightly larger. Red reflex was present in both eyes but less bright in the right eye. The retinas appeared intact and without obvious pathology; however, the retina in the right eye was more difficult to view. The right cornea did not stain with fluorescein dye. Intraocular pressure (IOP) on Schiotz tonometry was approximately 8 mm Hg in the right eye and 14 mm Hg in the left eye (normal, 10-20 mm Hg).
Laboratory studies The CBC results were within normal limits, including RBC, 5.13106/µL; WBC count, 5,300/µL; platelets, 1523103/µL; hemoglobin, 14 g/dL; hematocrit, 42%; and ESR, 10 mm/h. Human leukocyte antigen B27 (HLA-B27) testing was negative.
DISCUSSION
Although conjunctival inflammation in the eyes has a wide differential diagnosis, the observant clinician can make a reasonably accurate diagnosis in our patient's case. Viral or bacterial infection must be a consideration but can be ruled out quickly by the history and physical examination findings. Most conjunctival viral infections affect both eyes, and the redness is usually across the entire conjunctiva as well as the inner surface of the eyelids. The eye typically has a gritty sensation (the feeling of sand in the eye), burning pain, and photophobia accompanied by mucous discharge. Bacterial infection can be unilateral or bilateral, is typically associated with purulent discharge, and usually involves a history of a foreign body in the eye or trauma. Corneal ulcer usually produces unilateral conjunctival redness and intense pain. The ulcer is visible on the cornea with direct light, oblique light, or fluorescein staining. Frequently, this condition is accompanied by decreased vision.
Our patient had no discharge, mild pain, limited ciliary injection, no history of trauma, and a clear cornea even with staining; therefore, infection was very unlikely. Manifestation as a unilateral red eye with pain suggests that the patient could have a sight-threatening condition. The three most likely diagnoses associated with this clinical presentation are chronic open-angle glaucoma (COAG), acute angle-closure glaucoma (AACG), and iritis (Table 1).
