Priority Topic: Red Eye

Key Feature 1: In addressing eye complaints, always assess visual acuity using history, physical examination, or the Snellen chart, as appropriate.
Skill: Clinical Reasoning
Phase: History, Physical

Key Feature 2a: In a patient with a red eye, distinguish between serious causes (ex: keratitis, glaucoma, perforation, temporal arteritis) and non-serious causes (i.e., do not assume all red eyes are caused by conjunctivitis): Take an appropriate history (ex: photophobia, changes in vision, history of trauma).
Skill: Clinical Reasoning
Phase: History

Key Feature 2b: In a patient with a red eye, distinguish between serious causes (ex: keratitis, glaucoma, perforation, temporal arteritis) and non-serious causes (i.e., do not assume all red eyes are caused by conjunctivitis): Do a focused physical examination (ex: pupil size, and visual acuity, slit lamp, fluorescein).
Skill: Clinical Reasoning
Phase: History

Key Feature 2c: In a patient with a red eye, distinguish between serious causes (ex: keratitis, glaucoma, perforation, temporal arteritis) and non-serious causes (i.e., do not assume all red eyes are caused by conjunctivitis): Do appropriate investigations (ex: erythrocyte sedimentation rate measurement, tonometry).
Skill: Clinical Reasoning
Phase: Investigation

Key Feature 2d: In a patient with a red eye, distinguish between serious causes (ex: keratitis, glaucoma, perforation, temporal arteritis) and non-serious causes (i.e., do not assume all red eyes are caused by conjunctivitis): Refer the patient appropriately (if unsure of the diagnosis or if further work-up is needed).
Skill: Clinical Reasoning
​Phase: Referral

Key Feature 3: In patients presenting with an ocular foreign body sensation, correctly diagnose an intraocular foreign body by clarifying the mechanism of injury (ex: high speed, metal on metal, no glasses) and investigating (ex: with computed tomography, X- ray examination) when necessary.
Skill: Clinical Reasoning
Phase: Hypothesis generation, Diagnosis

Key Feature 4: In patients presenting with an ocular foreign body sensation, evert the eyelids to rule out the presence of a conjunctival foreign body.
Skill: Clinical Reasoning, Psychomotor Skills/Procedure Skills
Phase: Hypothesis generation, Physical

Key Feature 5: In neonates with conjunctivitis (not just blocked lacrimal glands or ‘‘gunky’’ eyes), look for a systemic cause and treat it appropriately (i.e., with antibiotics).
Skill: Clinical Reasoning
​Phase: Hypothesis generation, Treatment

Key Feature 6: In patients with conjunctivitis, distinguish by history and physical examination between allergic and infectious causes (viral or bacterial).
Skill: Clinical Reasoning
Phase: Diagnosis, History

Key Feature 7: In patients who have bacterial conjunctivitis and use contact lenses, provide treatment with antibiotics that cover for Pseudomonas.
Skill: Clinical Reasoning
Phase: Treatment

Key Feature 8: Use steroid treatment only when indicated (ex: to treat iritis; avoid with keratitis and conjunctivitis).
Skill: Clinical Reasoning
Phase: Treatment

Key Feature 9: In patients with iritis, consider and look for underlying systemic causes (ex: Crohn’s disease, lupus, ankylosing spondylitis).
Skill: Clinical Reasoning
Phase: Hypothesis generation

A common presenting concern in primary care is that of a red eye, which has a decent differential diagnosis. As for most presenting complaints, it's important to take a history that pertains to the presentation, including any inciting factors (ex: trauma) that may have contributed to the concern. Following the history comes the physical exam, which always includes testing visual acuity, inspecting the eyes, and assessing pupillary reactivity to light. In an emergency department setting, a slit lamp examination may also be done +/- using fluorescein to assess for corneal abnormalities, but in the primary care office the penlight can be used in place of the slit lamp to visualize the anterior portion of the eye at least. This can help assess for corneal abnormalities, but if you have a high index of suspicion, it is best to refer the patient to the ED to be examined with the slit lamp anyway. 

The standard of care for assessing visual acuity is the Snellen chart. If there isn't a Snellen chart anywhere nearby, you can simply have the patient read objects both near and far to check their near- and far-sighted vision, respectively, each eye at a time. And, if triaging patients over the phone, the best thing you can do is to ask the patient if there is a change in their vision and have them test it as you guide them to do so. Make sure they are wearing corrective glasses if they usually need them to read near or far. And bottom line really is that you should assess visual acuity as best as is feasible, and document your findings, no matter the eye concern.

As a primary care provider, after having done my focused history and physical exam, it is in fact quite simple to assess for whether or not a red eye is something I can treat right then and there, or if the patient's presentation warrants urgent referral to an Ophthalmologist. The 4 criteria that tell me I can manage the concern are:

1. Vision is unaffected
2. There is no objective foreign body sensation or photophobia
   1. An objective foreign body sensation means the patient cannot spontaneously keep their eye open in a brightly or dimly lit room, versus the subjective sensation as though it feels like there is something in the eye or that light bothers them, but still they can tolerate keeping their eye open without significant distress. An objective foreign body sensation warrants detailed historical assessment for the mechanism of injury, inspecting the eye and flipping the lid to look for an obvious and easily removable foreign body, +/- referring the patient to the emergency department for urgent assessment. 
   2. Photophobia means the patient cannot spontaneously keep their eye open in a brightly lit room, but that they can spontaneously keep their eye open in a dimly lit room. This suggests iritis, which itself is due to another (autoimmune) cause that requires further assessment. Firstly, the patient ought to be referred to an Ophthalmologist to confirm there is indeed true anterior uveitis. The treatment for autoimmune conditions is often immune-modulator therapy, such as topical steroids for the eye. Steroids are not without consequence, so having a complete Ophthalmology assessment prior to the initiation of steroids is a good eye-dea.
3. There is no corneal opacity, hypopyon, or hyphema (the latter two being a layer of white or red blood cells in the anterior chamber of the eye)
4. The pupil is reactive to light

Sometimes further investigations needs to be done, depending on the eye complaint. However, in the setting of a red eye, the concerns that would prompt me to further investigate would be ones for which I would be sending the patient for more urgent care anyway. The only exception to this would be in a patient who presents with risk factors or an atypical presentation of what would otherwise likely be benign disease. When it comes to a seemingly benign eye complaint that doesn't respond to basic management, a referral to Ophthalmology is also warranted.

Among the diagnoses that primary care physicians can make and proceed to treat without referral to Ophthalmology is conjunctivitis, be it of allergic, viral, or bacterial etiology. The cardinal features, of these three types of conjunctivitis, respectively, are mucoserous discharge with pruritus, mucoserous discharge in the setting of an upper respiratory tract infection and without pruritus, and mucopurulent discharge all day. The treatment varies depending on the type, but first-line is typically topical treatment(s). If a diagnosis of bacterial conjunctivitis is made, it is important to determine whether or not the patient wears contact lenses. If so, they are at risk for Pseudomonas conjunctivitis, and the topical antibiotic therapy that is chosen should cover for this organism.

An exception to using topical antibiotic therapy as the first-line treatment for bacterial conjunctivitis is in the setting of neonatal bacterial conjunctivitis, in which case one should always have suspicion that this could be part of a systemic infection. According to UpToDate, "C. trachomatis should be suspected in an infant less than one month of age with conjunctivitis if there is the possibility of exposure to the organism, specifically if the mother has a history of untreated C. trachomatis infection, or no prenatal care. If there has been no prenatal care or a maternal history of Neisseria gonorrhoeae (N. gonorrhoeae), the exudate also should be examined with Gram stain and cultured using selective medium to detect N. gonorrhoeae." If there is a high enough clinical suspicion of swabbing for the ocular discharge for Chlamydia and Gonorrhea, the neonate should be sent to a pediatric ED as empiric therapy is with IV antibiotics.