A 58-year-old woman with hypertension and diabetes presents with sudden loss of vision in the left eye. Fundoscopy shows retinal whitening with a cherry-red spot at the macula. Visual field testing reveals a complete loss of vision in the left eye. What is the most common arterial site of occlusion in this presentation?

Explanation

## Central Retinal Artery Occlusion (CRAO): Epidemiology & Pathology ### Clinical Presentation - **Sudden, painless, complete vision loss** in one eye - **Cherry-red spot** at the macula (area of retinal whitening with preserved foveal perfusion) - **Retinal whitening** (edema) in distribution of occluded vessel - **Afferent pupillary defect (APD)** present ### Most Common Site: Central Retinal Artery at the Optic Disc **Key Point:** CRAO at the **optic disc level** is the most common arterial occlusion in retinal vascular disease, accounting for ~1–2 per 100,000 population annually. ### Why CRA Occlusion Is Most Frequent | Factor | Impact | |--------|--------| | **Vessel caliber** | CRA is the main trunk; narrower than ophthalmic artery → more prone to thromboembolism | | **Flow dynamics** | CRA has slower flow velocity at the optic disc → higher risk of stasis and clot formation | | **Atherosclerotic burden** | CRA is a terminal vessel with limited collaterals; atherosclerotic plaques lodge easily | | **Anatomical vulnerability** | CRA enters the optic nerve at the disc; this is a natural "choke point" for emboli | | **Frequency in literature** | CRAO accounts for ~60–70% of acute retinal artery occlusions; BRA accounts for ~30–40% | **High-Yield:** CRAO causes **complete monocular vision loss** (not a field defect, but total blindness in one eye), whereas branch retinal artery occlusion (BRAO) causes **sectoral field loss** respecting vascular territories. ### Mechanism of Cherry-Red Spot 1. CRA occlusion → retinal ischemia → retinal whitening (edema) throughout posterior pole 2. Fovea receives dual blood supply: CRA and choroidal circulation (via choriocapillaris) 3. Choroid remains perfused → fovea appears **red** (cherry-red) against white ischemic retina 4. This is pathognomonic for CRAO ### Etiology & Risk Factors **Mnemonic: CRAO Causes = ATHEROSCLEROSIS** - **A**therosclerosis (most common) - **T**hromboembolism (from carotid plaques, cardiac sources) - **H**ypertension - **E**mboli (cardiac, arterial) - **R**heumatic heart disease - **O**cular ischemic syndrome - **S**yphilis (rare) - **C**arotid dissection - **L**upus / vasculitis - **E**ndocarditis - **R**adiation - **O**ral contraceptives (in young women) - **S**troke / TIA history - **I**nflammatory bowel disease - **S**ickle cell disease ### Clinical Pearl CRAO is an **ophthalmic emergency**. Immediate management includes ocular massage, anterior chamber paracentesis, and IV acetazolamide to lower IOP and dislodge emboli. Prognosis is poor; most patients retain light perception or worse vision. ### Why Other Sites Are Wrong ```mermaid flowchart TD A["Retinal Artery Occlusion"]:::outcome --> B{"Which vessel?"}:::decision B -->|"CRA at optic disc"| C["Complete monocular vision loss<br/>Cherry-red spot<br/>Retinal whitening throughout"]:::action B -->|"Branch retinal artery"| D["Sectoral field loss<br/>Respects vascular territory<br/>Partial vision retained"]:::action B -->|"Ophthalmic artery"| E["Rare; affects multiple vessels<br/>Often with orbital ischemia"]:::outcome B -->|"Posterior ciliary artery"| F["Causes optic nerve ischemia<br/>Not retinal whitening pattern"]:::outcome C --> G["Most common arterial occlusion"]:::urgent ``` [cite:Duke Ophthalmology Ch 10 - Retinal Vascular Disease]