Ophthalmology Diagnostic Algorithms
Five symptom-led decision trees for the eye complaints that walk into an emergency department or a family practice, where the first question is not "what is it" but "how fast does this need an ophthalmologist". Answer one branching question and the tree returns a differential sorted by urgency, with the action each diagnosis demands.
Urgency tiers are: critical (same-day, sight- or life-threatening), urgent (within 24 to 48 hours), important (routine referral), and monitor (observe and safety-net).
Sudden Vision Loss
Is the vision loss PAINFUL?
PAINFUL
- Critical — Acute Angle Closure Glaucoma. Rock-hard eye + N&V + mid-dilated pupil + corneal haze. IOP 40–60+ mmHg. Timolol + brimonidine + dorzolamide + Diamox 500mg PO + IV mannitol if needed → LPI definitive.
- Critical — Chemical Injury. IRRIGATE NOW — Morgan lens, 2L+ saline per eye, target pH 7.0–7.4. Alkali penetrates continuously. Do not examine before irrigating.
- Critical — Orbital Cellulitis. Proptosis + restricted painful EOMs + fever → CT orbits with contrast + IV broad-spectrum antibiotics. RAPD = optic nerve at risk = surgical urgency.
- Critical — Endophthalmitis. Post-op or traumatic. Hypopyon + cloudy media. VA ≥ HM → vitreous tap + inject vancomycin + ceftazidime. VA < HM → pars plana vitrectomy.
- Urgent — Optic Neuritis. Pain worse on eye movement + RAPD + color desaturation. IV methylprednisolone 1g/day × 3 days. Oral steroids ALONE = CONTRAINDICATED (ONTT).
PAINLESS
- Critical — CRAO. Cherry-red spot + diffuse retinal whitening. 90-min window. Ocular massage + AC paracentesis + IV acetazolamide. ESR/CRP if >50 (rule out GCA). Full stroke protocol.
- Critical — GCA / AAION. Age >50 + jaw claudication + elevated ESR/CRP + pallid disc swelling. IV methylprednisolone 1g/day NOW. Do not wait for biopsy — fellow eye at risk within hours.
- Urgent — Retinal Detachment. Flashes + floaters + curtain. Shafer's sign (tobacco dust). Macula-ON → operate SAME DAY. Macula-OFF → urgent surgery. B-scan if media hazy.
- Urgent — Amaurosis Fugax. Transient monocular loss = ocular TIA. Hollenhorst plaque. Carotid Doppler + cardiac echo + ECG/Holter. Rule out GCA if >50. Aspirin.
- Important — CRVO. "Blood and thunder" fundus — 4-quadrant hemorrhages + disc edema. Anti-VEGF injections (bevacizumab/aflibercept) first-line for macular edema. PRP if neovascularization.
- Important — NAION. Altitudinal defect on waking (nocturnal BP dip). Fellow eye: small crowded disc at risk. NAION: optimize vascular risk factors, stop PDE5 inhibitors. AION (GCA): steroids now.
Acute Red Eye
Is VISION REDUCED?
YES — vision reduced
- Critical — Chemical Injury. Irrigate immediately — 2L+ saline, Morgan lens, target pH 7.0–7.4. Alkali > Acid severity. Limbal ischemia = Roper-Hall grading. Topical Abx + cycloplegic + steroids.
- Critical — AACG. Rock-hard eye + mid-dilated pupil + corneal haze. IOP 40–60+ mmHg. Timolol + brimonidine + dorzolamide + Diamox + IV mannitol → laser peripheral iridotomy.
- Critical — Endophthalmitis. Post-op or post-traumatic. Hypopyon + cloudy vitreous. Tap + inject (VA ≥ HM) or vitrectomy (VA < HM). Vancomycin + ceftazidime intravitreally.
- Critical — Orbital Cellulitis. Proptosis + restricted EOMs + fever. CT orbits + IV Abx. RAPD = surgical urgency. Risk: cavernous sinus thrombosis, meningitis.
- Urgent — Corneal Ulcer. White stromal infiltrate + epithelial defect. CL wearer = Pseudomonas: ciprofloxacin or moxifloxacin. Large/central: culture first. NO patch for CL wearers.
- Urgent — HSV Keratitis. Dendritic ulcer with terminal end bulbs. Topical ganciclovir + oral acyclovir 400mg 5×/day. NEVER steroids over active epithelial defect.
NO — normal vision
- Monitor — Conjunctivitis. Bacterial: purulent + papillary → topical erythromycin or ciprofloxacin. Viral: watery + follicles + preauricular node → supportive only. Allergic: bilateral itching → antihistamines.
- Monitor — Corneal Abrasion. Epithelial defect, no infiltrate, no cells in AC. Lubrication + erythromycin ointment. Ciprofloxacin for CL wearers. NO patching for CL wearers. Heals in ~24h.
- Monitor — Subconj Hemorrhage. Flat red patch, normal vision, no pain. Reassurance. Posterior edge not visible → shield eye, rule out open globe. Recurrent → coagulation workup + BP check.
- Monitor — Traumatic Iritis. Cells + flare in AC post-blunt trauma. Rule out hyphema + lens dislocation first. Topical prednisolone acetate + cyclopentolate. Self-limiting ~1 week.
- Important — Uveitis (AAU). Ciliary injection + cells/flare + KPs. Fine KPs = HLA-B27 linked; mutton-fat KPs = granulomatous (sarcoid/TB). Topical steroids + cycloplegic. Workup if recurrent/bilateral.
Anisocoria + Ptosis
Which pupil is ABNORMAL?
LARGE pupil (mydriasis)
- Critical — CN III Palsy (compressive). Down/out deviation + complete ptosis + blown pupil (mydriasis). PComm aneurysm or uncal herniation. MRI brain + MRA/CTA immediately. Aberrant regeneration = mass, not vascular.
- Monitor — Pharmacologic mydriasis. Unilateral dilation, NO ptosis, NO paresis. Atropine, scopolamine patch, dilating drops. Pilocarpine 1% test: pupil fails to constrict = pharmacologic.
- Monitor — Adie's Tonic Pupil. Poorly reactive pupil, young woman, knee areflexia. Pilocarpine 0.1% (dilute) constricts the affected eye (denervation hypersensitivity). Benign.
- Monitor — Traumatic mydriasis. Iris sphincter rupture post-blunt trauma. Irregular pupil margin. Monitor for hyphema + iritis. Usually benign, may be permanent.
SMALL pupil (miosis)
- Urgent — Horner Syndrome. Miosis + mild ptosis + anhidrosis (ipsilateral face). PAINFUL Horner = carotid dissection → CTA/MRA neck NOW. Painless + upper extremity = Pancoast tumor. Cocaine confirms; Paradrine localizes.
- Monitor — Pharmacologic miosis. Pilocarpine drops, opiates, organophosphates. History-guided diagnosis. Bilateral miosis in opioid overdose with CNS depression.
- Important — Anterior Uveitis. Posterior synechiae or ciliary spasm cause miosis. Cells + flare + KPs on slit lamp. Perilimbal (ciliary) injection. Cycloplegics to relieve spasm and prevent synechiae.
- Monitor — Physiologic. Asymmetry <1mm, both pupils react normally to light. Consistent in all lighting conditions. No other findings. No workup needed.
New Diplopia
Is there PTOSIS or ANISOCORIA?
YES — ptosis or anisocoria
- Critical — CN III Palsy (aneurysm). Down/out + complete ptosis + blown pupil (large non-reactive) → PComm aneurysm. MRI + MRA/CTA immediately. Even partial CN3 + any pupil involvement = emergency.
- Urgent — Horner + CN4/6. Miosis + mild ptosis + diplopia. Cavernous sinus lesion, carotid dissection, or Pancoast. CTA/MRA. Multiple CN palsies in same orbit = cavernous sinus until proven otherwise.
- Critical — GCA (CN ischemia). Age >50 + headache + jaw claudication + CN palsy. ESR + CRP immediately. IV methylprednisolone NOW — do not wait for biopsy.
- Important — Myasthenia Gravis. Fatigable ptosis worse by end of day, variable diplopia. Ice test (ice pack over lid → improved ptosis). Anti-AChR antibodies. CT chest (thymoma). Pyridostigmine.
NO — isolated CN palsy
- Important — CN VI (Abducens) Palsy. Esotropia, horizontal diplopia, cannot abduct. Most common isolated CN palsy. Vascular (DM/HTN) usually resolves in 3 months. IIH false localizer — check papilledema. Children: rule out pontine glioma.
- Important — CN IV (Trochlear) Palsy. Vertical diplopia worse on downgaze (reading, stairs). Head tilt to opposite side. Most common traumatic CN palsy. 3-step Parks-Bielschowsky test localizes. Prism glasses. 3 months observation if vascular etiology.
- Urgent — Orbital Blowout Fracture. Post-blunt trauma. IR entrapment → upgaze restriction. CT orbits. Children: white-eyed blowout (trapdoor) → vagal bradycardia → urgent OR. Adults: NO nose blowing.
- Important — Thyroid Eye Disease. Restrictive myopathy (IR most common). Proptosis + lid lag + chemosis. TSH + free T4. CT orbits: enlarged extraocular muscles (belly, not tendon). Steroids or orbital decompression.
Floaters + Flashes
Is there a CURTAIN or FIELD DEFECT?
YES — curtain / shadow
- Urgent — Retinal Detachment. Corrugated gray retina on indirect. B-scan if media hazy. Macula-ON → same-day OR. Macula-OFF → urgent (days). Pneumatic retinopexy / scleral buckle / vitrectomy by anatomy.
- Urgent — Retinal Tear (no RD). Shafer's sign (tobacco dust): pigment cells in vitreous = retinal tear until proven otherwise. Urgent indirect ophthalmoscopy. Laser photocoagulation or cryotherapy prophylaxis.
- Important — Vitreous Hemorrhage. Dense floaters or dark haze. B-scan ultrasound immediately to look for underlying RD or fibrovascular membrane. Common causes: DM, RVO, retinal tear, posterior vitreous detachment.
- Important — CRVO. Sudden blurred vision + floaters + "blood and thunder" fundus. Anti-VEGF for macular edema. Watch for neovascularization → rubeosis → NV glaucoma (PRP + anti-VEGF).
NO — floaters only
- Monitor — Posterior Vitreous Detachment. Weiss ring floater (circle of condensed vitreous from optic disc). Most common in myopes >40. Risk of retinal tear at time of PVD — dilated fundus exam mandatory. 95% benign.
- Important — Uveitis (intermediate/posterior). Snowball vitreous opacities, vitritis, cystoid macular edema. Systemic workup: sarcoid (ACE, CXR), TB (IGRA), syphilis (RPR/VDRL), Lyme. Topical ± systemic steroids.
- Important — CMV Retinitis. HIV+ with CD4 <50. "Pizza pie" fundus: white necrosis + hemorrhage. IV ganciclovir induction → oral valganciclovir maintenance. ART to raise CD4 and prevent relapse.
- Critical — Endophthalmitis (early). Floaters + pain post-op or post-injection. ANY post-procedural floaters with discomfort = endophthalmitis until proven otherwise. Urgent slit-lamp exam.
Related tools