A red eye can be an elusive entity for first-year residents. Various pathologies can manifest as the red eye, and it is critical for residents to be able to ask the appropriate questions, perform a focused exam and discern which of the various diagnoses the patient may have.
Here are four common conditions that can cause a red eye.
1. Conjunctivitis
Conjunctivitis is defined as inflammation of the conjunctival tissue. It is associated with the development of conjunctival follicles or papillae, which can help ellucidate the etiology of conjunctivitis. Papillae form when the conjunctival epithelium covers fibrovascular cores with blood vessels and the conjunctival stroma contains eosinophils, lymphocytes and plasma cells. Follicles form when the conjunctival epithelium covers lymphoid follicles and is surrounded by stromal lymphocytes and plasma cells.
Always turn the upper eyelid inside out to see if follicles or papillae are present on the upper eyelid palpebral conjunctiva. Always pull down the lower eyelid to assess for similar findings in the lower eyelid palpebral conjunctiva. Sometimes there can be associated swelling of the bulbar conjunctiva, known as conjunctival chemosis.
Follicular conjunctivitis can be driven by viral (i.e., adenoviral, herpetic, molluscum), chlyamdial or allergic etiologies; severe blepharitis and/or demodex blepharitis can also cause an associated conjunctivitis. Papillary conjunctivitis can be allergy related (i.e., atopic or vernal conjunctivitis) but can also be caused by foreign bodies in the eye, like contact lenses or sutures, or by bacterial infections.
It is important to distinguish if the conjunctivitis is acute or chronic, as some cases of chronic conjunctivitis can be caused by atypical infections or be a rare manifestation of conjunctival malignancy. Bacterial conjunctivitis tends to be associated with purulent discharge, while viral and allergic conjunctivitis can have clearer mucoid discharge.
Treatment for conjunctivitis is largely supportive (i.e., artificial tears, cool compresses); however, systemic and/or topical antibiotics may be needed for bacterial conjunctivitis, and topical and/or oral antihistamines may be needed for allergic cases. If a foreign body in the eye is the cause, it needs to be removed.
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Slit-lamp photograph documenting a red eye with a new dendrite on the cornea secondary to herpesviral keratitis
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Slit-lamp photograph documenting an injected eye with a nonhealing epithelial defect superiorly with central haze and corneal neovascularization secondary to neurotrophic keratitis.
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Images courtesy of Nandini Venkateswaran, MD
2. Keratitis
Various causes of keratitis can cause a red eye. Common causes include herpetic keratitis or corneal ulcers.
Ask patients about their history of eye trauma, contact lens wear with poor hygiene or recent eye surgery. Examine the eye carefully for conjunctival injection or ciliary flush, which is suggestive of intraocular inflammation. The focus of your findings in keratitis will be on the cornea. Look for dendrites or pseudodendrites with fluorescein staining suggestive of herpetic keratitis.
If an ulcer is suspected, you can see corneal infiltrates with associated epithelial defects; there can also be anterior chamber cell or hypopyon formation. In addition, there can at times be a follicular or papillary conjunctival reaction in cases of keratitis. In these scenarios, expedient corneal cultures and initiating topical antibiotics and/or topical/ oral antivirals is critical for rehabilitation. Don’t forget to check corneal sensation with a wisp of cotton before putting in numbing drops.
3. Uveitis
Patients with anterior uveitis typically present with a red eye and ciliary flush. Associated symptoms include eye pain, soreness, blurred vision and photophobia.
Check the cornea carefully for keratic precipitates or corneal edema. There will be cell and/or flare in the anterior chamber. The iris can show signs of nodules, atrophy or posterior synechiae depending on the etiology of the uveitic process. There can sometimes be associated spillover vitreous inflammation. In cases of posterior uveitis, the eye can also be red, but the majority of inflammation will be appreciated in the vitreous cavity and retinal tissues.
Unlike conjunctivitis, which will have a follicular/papillary reaction, uveitis will have only injection and usually no associated conjunctival papillae or follicles. Ask your patients about a history of autoimmune diseases that can cause uveitis (i.e., rheumatoid arthritis, sarcoidosis, lupus, etc.) and obtain relevant lab work as well.
4. Subconjunctival Hemorrhage
Subconjunctival hemorrhages are common and are a frequent cause of urgent patient visits to the office. These hemorrhages can occur spontaneously or as a result of eye-rubbing or exertional activity, causing a rupture of conjunctival blood vessels. Sometimes patients who have undergone recent eye surgery can also have subconjunctival hemorrhages associated with conjunctival manipulation or subconjunctival injections.
Patients who are on blood thinners may be more predisposed. It is important to ask patients about a history of high blood pressure or a blood coagulation disorder, as these disorders can be associated with recurrent subconjunctival hemorrhages. When examining your patient, redness will typically be appreciated on the bulbar conjunctiva and can be focal or diffuse. The palpebral conjunctiva tends to be unaffected, and there is no associated intraocular inflammation. Ensure there are no conjunctival lacerations or signs of ocular injury causing the hemorrhage.
Advise patients that these hemorrhages are self-limited and will resolve with no treatment over 10 to 14 days (about 2 weeks). Artificial tears can be used to lubricate the eyes in most cases if there is any associated eye irritation.
As a first-year resident, hone in on which part of the eye is red. This will help you easily distinguish the cause and initiate appropriate treatment. These conditions can be common, and if you can be thoughtful in your approach, you will shine when encountering a red eye.
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Nandini Venkateswaran, MD, is a cataract, cornea and refractive surgeon at Massachusetts Eye and Ear Infirmary in Waltham, Mass. She is also a clinical instructor of ophthalmology at Harvard Medical School.