What is the management for a unilateral very red eye in a patient with unknown demographic and medical history, potentially with underlying conditions such as trauma, previous eye surgery, diabetes (Diabetes Mellitus), or hypertension (Hypertension)?

Management of Unilateral Very Red Eye

A unilateral very red eye requires urgent ophthalmology referral within 24 hours if any of the following are present: visual acuity loss, moderate-to-severe pain (beyond irritation), photophobia, or visible corneal opacity/damage. 1

Immediate Triage Using the RAPID Acronym

The 2024 expert consensus provides a clear framework for urgent referral 1:

• Redness plus any of:
• Acuity loss or worsening
• Pain (ocular pain, moderate or severe, more than irritation)
• Intolerance of light (photophobia)
• Damaged cornea visible or opacity

If any RAPID criterion is met, refer to ophthalmology within 24 hours. 1 This represents a true ocular emergency requiring specialist evaluation to prevent permanent vision loss.

Critical Distinction: Unilateral vs. Bilateral Presentation

Unilateral eye symptoms are unlikely to represent common bilateral conditions like dupilumab-related ocular surface disease or simple conjunctivitis, and should be managed through existing emergency pathways. 1 The unilateral presentation suggests:

• Infectious keratitis (bacterial, viral, fungal)
• Acute angle-closure glaucoma
• Anterior uveitis/iritis
• Corneal ulceration or abrasion
• Scleritis or episcleritis
• Retinal artery or vein occlusion
• Traumatic injury

Essential Baseline Assessment Before Referral

History Elements to Document

Obtain specific details about pain severity, duration of redness, visual changes, photophobia, and discharge character. 2, 3, 4

• Severe pain not relieved by topical anesthetics mandates immediate ophthalmology referral 2
• History of herpes simplex virus eye disease requires urgent specialist evaluation 1
• Recent ocular surgery or trauma necessitates same-day ophthalmology assessment 2, 3
• Immunocompromised status increases risk of sight-threatening infections 1

Physical Examination Priorities

Visual acuity measurement is mandatory and represents the strongest prognostic factor for outcomes. 1

Pupil examination for relative afferent pupillary defect indicates severe retinal or optic nerve pathology requiring emergency evaluation. 1

Intraocular pressure measurement is essential when glaucoma is suspected, particularly with mid-dilated or distorted pupil. 1, 2

Examine pupil shape and reactivity—a distorted or non-reactive pupil requires immediate ophthalmology referral. 2

Assess corneal clarity using a penlight—loss of the natural corneal transparency and specular reflex demands urgent specialist evaluation. 5

Specific High-Risk Scenarios Requiring Emergency Referral

Suspected Acute Angle-Closure Glaucoma

Mid-dilated fixed pupil, severe pain, corneal edema, and elevated intraocular pressure constitute an ophthalmologic emergency. 2, 4

Suspected Bacterial Keratitis

Corneal involvement with purulent discharge requires immediate ophthalmology consultation and treatment as for bacterial keratitis. 1

Copious purulent discharge, especially in the context of possible gonococcal infection, requires daily follow-up until resolution. 1

Suspected Anterior Uveitis/Iritis

Ciliary injection (deep perilimbal redness), photophobia, and pain suggest iritis requiring urgent specialist evaluation. 6

Perform slit-lamp biomicroscopy with iris examination before dilation when neovascularization is suspected. 1

Suspected Retinal Artery or Vein Occlusion

Acute symptomatic retinal artery occlusion requires immediate referral to a stroke center or emergency department, as stroke risk may be as high as 25%. 1

Patients should be referred for urgent cardiovascular evaluation within 1 week of onset, as stroke risk is highest in the first 7 days. 1

Management Pitfalls to Avoid

Never prescribe topical corticosteroids without ophthalmology consultation—infectious causes must be ruled out before immunosuppression. 1

Do not delay referral to obtain ancillary testing like fluorescein angiography or OCT in acute presentations—transfer to a stroke center or ophthalmology takes priority. 1

Avoid attributing unilateral red eye to simple conjunctivitis without careful examination—bilateral presentation is typical for viral/bacterial conjunctivitis. 1, 2

Do not miss signs of giant cell arteritis in patients over 50 years with vision loss—obtain immediate ESR, CRP, and CBC with platelets. 1

When Outpatient Management May Be Appropriate

If pain is minimal, vision is normal, cornea is clear, pupil is normal, and no RAPID criteria are met, consider simple conjunctivitis or subconjunctival hemorrhage. 2, 3

For presumed viral or bacterial conjunctivitis without warning signs, advise return in 3-4 days if no improvement occurs. 1

Patients with recurrent episodes, lack of response to therapy, or conjunctival scarring require ophthalmology referral even without acute warning signs. 1