Acute & Chronic Vision Loss
A STEP 2 CK-focused lesson on acute vs chronic vision loss, organized by tempo and pain, covering the classic buzzwords, fundus findings, and next-best-step management for CRAO, CRVO, retinal detachment, vitreous hemorrhage, amaurosis fugax/GCA, acute angle-closure glaucoma, optic neuritis, and the chronic causes (open-angle glaucoma, cataract, AMD, diabetic retinopathy).
Framework: triage by tempo and pain
Vision loss is triaged along two axes: tempo (sudden vs gradual) and pain. Sudden, painless, monocular loss is a vascular/retinal emergency — think "eye stroke" (CRAO, CRVO, retinal detachment, vitreous hemorrhage) and act fast. Sudden loss with a painful red eye points to acute angle-closure glaucoma; pain on eye movement points to optic neuritis. Gradual, painless loss is usually cataract, primary open-angle glaucoma, age-related macular degeneration (AMD), or diabetic retinopathy.
Two exam reflexes anchor the whole topic:
- A relative afferent pupillary defect (RAPD / Marcus Gunn pupil) localizes the lesion to the optic nerve or a large retinal process — not to the media (cataract) or macula alone.
- In anyone >50 with sudden vision loss, screen for GCA (ESR + CRP). Its arteritic AION is itself painless, so ask about headache, scalp tenderness, and jaw claudication — and treat before it blinds the fellow eye.
Always compare with the other eye, and treat reversible causes within minutes to hours.
- Cherry-red spot + pale, milky retina, boxcar vessels, sudden painless mono loss → central retinal artery occlusion (CRAO) — a retinal stroke
- "Blood-and-thunder" fundus (diffuse hemorrhages, dilated tortuous veins, cotton-wool spots) → central retinal vein occlusion (CRVO)
- Flashes (photopsia) + floaters + a "curtain/shadow" over the field → retinal detachment
- Sudden floaters/"cobwebs" with loss of the red reflex, esp. proliferative diabetic → vitreous hemorrhage
- Transient monocular "curtain descending" that resolves → amaurosis fugax (carotid embolus; Hollenhorst plaque)
- Age >50 + jaw claudication + scalp tenderness + high ESR/CRP → GCA / arteritic AION
- Pain on eye movement + ↓ color (red desaturation) + RAPD, young woman → optic neuritis (MS)
- Red painful eye, mid-dilated fixed pupil, halos, nausea, rock-hard globe → acute angle-closure glaucoma
Acute painless monocular vision loss
| Condition | Hallmark finding | Typical cause | Next best step |
|---|---|---|---|
| CRAO | Cherry-red spot, pale retina | Embolus (carotid/cardiac) | Treat as a stroke (urgent stroke workup); ocular massage, ↓ IOP, emergent ophtho; ESR/CRP if >50 |
| CRVO | "Blood-and-thunder" hemorrhages | Venous thrombosis (HTN, glaucoma) | Ophtho; anti-VEGF for macular edema; control HTN |
| Retinal detachment | Flashes, floaters, gray elevated retina | Retinal tear (myopia, trauma) | Emergent ophtho; surgical reattachment |
| Vitreous hemorrhage | Floaters, absent red reflex | Proliferative diabetic retinopathy, tear | B-scan ultrasound; ophtho; treat neovascularization |
| Amaurosis fugax | Transient "curtain," then resolves | Carotid embolus (plaque) | Carotid duplex; antiplatelet; TIA workup |
Vignette: A 74-year-old woman reports a new right temporal headache, scalp tenderness when combing her hair, and jaw pain that forces her to stop chewing. Yesterday a brief "shade" crossed the right eye; today that eye is nearly blind. ESR is 92 mm/hr, and the optic disc is pale and swollen.
Diagnosis: Giant cell (temporal) arteritis causing arteritic anterior ischemic optic neuropathy (AION).
Next best step: Start high-dose corticosteroids immediately — do NOT wait for the biopsy. The confirmatory temporal artery biopsy stays positive for weeks after steroids are begun, so treating first costs nothing and prevents rapid, irreversible blindness of the fellow eye. Order ESR and CRP (usually markedly elevated); because inflammation is patchy (skip lesions), a generous specimen is taken so a single biopsy is not falsely negative.
Vignette: A 62-year-old becomes acutely ill in a dark movie theater with severe left eye pain, headache, nausea, and vomiting, and sees halos around lights. The eye is red, the cornea hazy, the pupil mid-dilated and fixed, and the globe feels rock-hard. IOP is 52 mmHg.
Diagnosis: Acute angle-closure glaucoma (pupillary block; precipitated by dim light or mydriatics).
Next best step: Lower the IOP urgently — systemic acetazolamide plus topical timolol + apraclonidine (or brimonidine); add pilocarpine once the pressure starts to fall (at very high IOP the iris sphincter is ischemic and unresponsive to it), ± IV mannitol. Definitive treatment is laser peripheral iridotomy. Avoid mydriatics/anticholinergics (atropine). The vomiting and fixed mid-dilated pupil are classic misdirection toward a GI or neurologic cause — check the IOP.
Vignette: A 27-year-old woman has subacute blurring of the left eye over several days with pain on eye movement. Colors look "washed out" (red desaturation), there is a central scotoma, and the swinging-flashlight test shows a left RAPD (Marcus Gunn pupil). The disc looks normal (retrobulbar).
Diagnosis: Optic neuritis — usually demyelinating and a frequent first presentation of multiple sclerosis.
Next best step: MRI of the brain/orbits with contrast to assess white-matter lesions and MS risk. Treat with IV methylprednisolone, which speeds recovery (though it does not change the final visual outcome). Oral prednisone alone is avoided — in the Optic Neuritis Treatment Trial it raised the recurrence rate. Vision typically recovers over weeks.
- Gradual peripheral/tunnel loss, ↑ cup-to-disc ratio, disc cupping → primary open-angle glaucoma; first-line drop = prostaglandin analog (latanoprost)
- Painless blur, glare/halos at night, ↓ red reflex (older age, smoking, steroids, diabetes) → cataract; definitive Tx = surgery
- Central vision loss + metamorphopsia (wavy lines on the Amsler grid): drusen = dry AMD (slow; AREDS2 vitamins slow progression); choroidal neovascularization/hemorrhage = wet AMD (anti-VEGF injections)
- Microaneurysms, dot-blot hemorrhages, hard exudates = nonproliferative; neovascularization = proliferative diabetic retinopathy → panretinal photocoagulation; macular edema → anti-VEGF
- AV nicking, copper/silver wiring, flame hemorrhages, cotton-wool spots → hypertensive retinopathy
Memorize the buzzword → diagnosis link — these are tested verbatim:
- "Cherry-red spot" → CRAO (also Tay-Sachs & Niemann-Pick storage diseases)
- "Blood-and-thunder" fundus → CRVO
- Marcus Gunn pupil (RAPD) → afferent defect = optic nerve disease (optic neuritis, large retinal lesion)
- Amsler-grid distortion (metamorphopsia) → macular disease (AMD)
- Hollenhorst plaque (bright cholesterol embolus at a vessel branch point) → amaurosis fugax / carotid source
- "Curtain coming down": transient & resolves = amaurosis fugax; permanent + flashes/floaters = retinal detachment
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