The Daily Differential — Monday, May 25, 2026

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Approach to the Patient with Vision Loss

Vision loss is a localization problem, not a single diagnosis. The high-yield distinction is monocular versus binocular, painful versus painless, and...

At the Bedside

First questions
One eye or both?
Sudden or gradual?
Painful or painless?
Central blur, field cut, curtain, floaters, flashes, color desaturation, or complete blackout?
Any headache, jaw claudication, eye movement pain, trauma, anticoagulation, or vascular risk?
Bedside exam
Visual acuity in each eye.
Pupils with attention to a relative afferent pupillary defect.
Confrontation fields.
Extraocular movements.
Slit lamp for anterior segment disease.
Fluorescein if corneal pathology is possible.
Tonometry if glaucoma is on the differential.
Fundus exam if possible; use ocular ultrasound when retinal detachment or vitreous hemorrhage is possible.
Must-not-miss diagnoses
CRAO: sudden painless monocular loss, RAPD, cherry-red spot, stroke equivalent.
Retinal detachment: flashes, floaters, curtain/shadow.
Giant cell arteritis: older patient, headache, jaw claudication, scalp tenderness, visual symptoms.
Optic neuritis: pain with eye movement, color desaturation, RAPD.
Acute angle closure glaucoma: eye pain, halos, nausea/vomiting, high IOP.
Endophthalmitis: post-op, post-injection, trauma, severe pain, red eye, reduced vision.
Disposition logic
Sudden painless monocular loss is an emergency until a retinal/vascular cause is excluded.
Any vision loss with headache/jaw claudication in an older patient should trigger GCA treatment while workup is in motion.
Flashes/floaters/curtain need urgent retinal evaluation.
Painful eye movement or neuro deficits should widen the differential beyond the eye.

A Classic Presentation

A 74-year-old man notices a curtain over his left eye after several flashes and floaters. He has no eye pain. Visual acuity is decreased in the left eye, pupils show a left RAPD, and bedside ultrasound suggests a detached retina. The ED treats this as an urgent retinal emergency and arranges same-day ophthalmology evaluation.

Study Directive

Practice the rapid vision-loss history: one eye or both, pain or no pain, sudden or gradual, field cut or acuity loss.
Rehearse the exam sequence: acuity, pupils, fields, EOMs, fluorescein, IOP, fundus, ultrasound.
Build a localization grid from memory: cornea, anterior chamber, retina, optic nerve, or brain.
Review the stroke-equivalent approach to CRAO and the urgent steroid pathway for GCA.

Key Medications

Methylprednisolone for visual symptoms from suspected giant cell arteritis: often 500–1,000 mg IV daily for 3 days, then high-dose oral therapy per consultant pathway.
Prednisone for suspected giant cell arteritis without severe visual compromise: commonly 40–60 mg PO daily, but follow local specialist guidance.
Aspirin: 325 mg PO once is commonly used when a vascular ocular event is suspected and hemorrhage is excluded; follow stroke protocol and contraindications.
Analgesia/antiemetics: symptom-directed, but do not let symptom control delay eye- or stroke-level evaluation.

High-Yield Pearls

Start with monocular vs binocular; that single step changes the differential dramatically.
A relative afferent pupillary defect is a red flag for optic nerve or major retinal disease.
Flashes, floaters, or a curtain means you should think retinal detachment until proven otherwise.

Board Question

Which feature most strongly suggests an optic nerve or retinal process rather than a simple conjunctivitis?

AItching and discharge
BPain relieved by topical anesthetic
CRelative afferent pupillary defect
DMild bilateral redness

Reveal answer

Correct: C

An RAPD implies asymmetric optic nerve or severe retinal dysfunction. It is not a feature of uncomplicated conjunctivitis.

3 of 4

Approach to the Red Eye

A red eye is usually benign, but the dangerous branch point is whether it is painful, photophobic, or associated with decreased vision. That combination...

At the Bedside

History that matters
Pain severity, photophobia, vision change, discharge, itching, contact lens use, trauma, chemical exposure, and systemic autoimmune disease.
Ask whether the pain is worse with light or with eye movement.
Exam
Visual acuity first.
Pupil shape and reactivity.
Pattern of injection: diffuse, ciliary flush, sectoral.
Fluorescein for abrasion or corneal ulcer.
Tonometry when glaucoma is possible.
Look for ciliary flush, corneal opacity, hypopyon, and scleral tenderness.
Common branches
Conjunctivitis: mild discomfort, discharge, preserved vision.
Keratitis/corneal ulcer: pain, photophobia, contact lens use, fluorescein uptake.
Anterior uveitis: consensual photophobia, ciliary flush, small pupil.
Acute angle closure glaucoma: severe pain, halos, nausea/vomiting, high IOP.
Scleritis: deep boring pain, autoimmune association, pain with eye movement.
Subconjunctival hemorrhage: painless, dramatic but benign.
Bedside rules
Contact lens wearer with pain is keratitis until proven otherwise.
Vision loss, corneal opacity, hypopyon, or severe pain are not routine conjunctivitis.
Do not give steroid drops without ophthalmology guidance.

A Classic Presentation

A 29-year-old contact lens wearer has one day of painful red eye, blurred vision, and photophobia. Fluorescein shows a central corneal defect with surrounding haze. The ED stops contact lens use, starts broad topical antibiotic coverage, and arranges urgent ophthalmology evaluation for infectious keratitis.

Study Directive

Practice naming the red-eye branch points from memory: pain, photophobia, vision loss, contact lenses, trauma, and IOP.
Review the exam sequence for red eye: acuity, pupils, fluorescein, IOP, slit lamp, and corneal inspection.
Learn the high-risk red-eye diagnoses and the one bedside clue that moves each up the list.
Be able to say why conjunctivitis is usually a diagnosis of exclusion when pain or vision changes are present.

Key Medications

Proparacaine 0.5% ophthalmic: 1 drop in the ED to facilitate exam; do not prescribe for routine outpatient use.
Fluorescein strip: use to detect abrasion or epithelial defect.
Erythromycin ophthalmic ointment: often 0.5-inch ribbon 4 times daily for uncomplicated abrasion or conjunctivitis when indicated.
Trimethoprim-polymyxin B drops: 1 drop every 6 hours for uncomplicated bacterial conjunctivitis in many adult pathways.
Ofloxacin or moxifloxacin drops: consider for contact lens-related bacterial keratitis per ophthalmology/local protocol.
Timolol, brimonidine, dorzolamide, acetazolamide: use only when acute glaucoma is in the differential and follow local pathway.

High-Yield Pearls

Pain + photophobia + decreased vision is not routine conjunctivitis.
A contact lens wearer with a red painful eye needs corneal ulcer thinking, not reassurance.
Steroid eye drops can make infectious corneal disease much worse if used blindly.

Board Question

A patient has a painful red eye, photophobia, decreased vision, and a corneal fluorescein defect. What should you worry about most?

ASimple viral conjunctivitis
BInfectious keratitis
CSubconjunctival hemorrhage
DDry eye only

Reveal answer

Correct: B

Pain plus photophobia plus a corneal epithelial defect should raise concern for keratitis or corneal ulcer, especially in contact lens wearers.

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Central Retinal Artery Occlusion

CRAO is an eye stroke. The retina is ischemic, the deficit is usually sudden and painless, and the patient may only get one chance at reperfusion or...

At the Bedside

Presentation
Sudden painless monocular vision loss or severe monocular blurring.
RAPD is common.
Fundus may show retinal whitening and a cherry-red spot, though the exam can be subtle early.
Immediate actions
Activate a stroke-level evaluation.
Involve ophthalmology and neurology/stroke team early.
Screen for giant cell arteritis in patients over 50 or with headache, scalp tenderness, or jaw claudication.
Check glucose, blood pressure, and basic vascular risk data.
Use local stroke protocols for vascular imaging and thrombolysis consideration.
Treatment reality
There is no consistently proven ED “vision rescue” maneuver.
Do not let low-yield bedside maneuvers delay stroke evaluation.
If the patient is a thrombolysis candidate and local systems support it, manage through the stroke pathway.
If GCA is suspected, start steroids urgently.
Disposition
Admission or transfer is generally appropriate because this is a vascular emergency with major secondary prevention implications.

A Classic Presentation

A 68-year-old with atrial fibrillation develops sudden painless loss of vision in the right eye while reading. Visual acuity is counting fingers, the pupil has a right RAPD, and the fundus suggests retinal ischemia. The ED activates stroke evaluation, involves ophthalmology, and treats the event as a vascular emergency rather than a benign eye complaint.

Study Directive

Practice identifying CRAO from a one-line vignette in under 10 seconds.
Review the exam findings that separate CRAO from retinal detachment, optic neuritis, and GCA.
Know your institution’s pathway for stroke activation, vascular imaging, and thrombolysis consultation.
Learn to say out loud: “CRAO is an eye stroke, not a benign eye complaint.”

Mechanism Pearl of the Day: The common thread today is localization: ear pain tells you whether the problem is canal, middle ear, mastoid, or referred; vision loss and red eye tell you whether the lesion is corneal, anterior chamber, retinal, optic nerve, or vascular. The bedside win is not naming the symptom, but identifying the anatomic compartment fast enough to protect function.

Key Medications

Aspirin: 325 mg PO once after hemorrhage is excluded if thrombolysis is not being given and there is no contraindication.
High-intensity statin: commonly initiated as part of secondary prevention once the stroke team is involved; exact drug/dose depends on local pathway.
Methylprednisolone or prednisone: if arteritic CRAO / GCA is suspected, use the GCA steroid pathway immediately.
Thrombolytic therapy: if offered, follow the stroke team and institutional dosing pathway rather than improvising.

High-Yield Pearls

Sudden painless monocular loss is a vascular emergency until proven otherwise.
CRAO and giant cell arteritis are linked through the same ischemic-risk framework.
Low-yield bedside maneuvers should not distract from the stroke pathway.

Board Question

What is the best framing for sudden painless monocular vision loss from suspected CRAO?

ARoutine outpatient ophthalmology follow-up
BEye stroke requiring urgent vascular evaluation
CA primary corneal disorder
DSimple migraine aura until proven otherwise

Reveal answer

Correct: B

CRAO is a vascular emergency and should be approached like a stroke, not like a routine clinic eye complaint.

Recent Literature

Review or guideline Central retinal artery occlusion
Indian J Ophthalmol, 2018 · cited 130×

Full text · open access
Recent clinical Treponemal Endovasculitis leading to branch artery occlusion: a rare manifestation of ocular syphilis
Oxf Med Case Reports, 2026

Full text · open access

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