A 68-year-old man with atrial fibrillation presents with sudden, painless loss of vision in the left eye. Fundoscopy reveals the finding marked **A** in the diagram — a bright red spot at the macula surrounded by a pale, edematous retina. Which of the following is the MOST APPROPRIATE immediate intervention to attempt vision salvage in this vascular emergency?

Explanation

## Why ocular massage and carbogen rebreathing is right The cherry-red spot at the macula (marked **A**) surrounded by pale, edematous retina is pathognomonic of central retinal artery occlusion (CRAO) — an ophthalmologic stroke. The fovea is an avascular pit supplied only by choroidal circulation, so it appears bright red against the ischemic white retina. In the critical 4–6 hour window, ocular massage (intermittent pressure on the closed eye) attempts to dislodge the embolus distally into smaller vessels, while carbogen rebreathing (or paper bag rebreathing) increases CO₂ and induces vasodilation to improve retinal perfusion. These are the first-line emergency maneuvers. Acetazolamide and anterior chamber paracentesis are adjunctive measures to lower intraocular pressure, but massage and carbogen address the primary pathology — the occluding embolus (Khurana Ophthalmology 7e; Harrison 21e Ch 32). ## Why each distractor is wrong - **Topical pilocarpine and systemic diuretics**: While IOP reduction via acetazolamide or paracentesis is part of CRAO management, pilocarpine (a miotic) and diuretics alone do not address the embolic occlusion and are not first-line emergency interventions. They are adjunctive only. - **Immediate temporal artery biopsy and high-dose steroids**: This is the correct approach for giant cell arteritis (GCA)-related CRAO, which presents with headache, temporal tenderness, jaw claudication, and elevated ESR in an older patient. This patient has atrial fibrillation (embolic source), not GCA features, so GCA-directed therapy is inappropriate and delays embolus-directed rescue. - **Oral antiplatelet therapy and neurology referral**: While secondary stroke prevention is essential after CRAO (patients have 15–25% stroke risk in 3 months), antiplatelet therapy does not salvage acute vision in the hyperacute window. This is a delayed, chronic management step, not an emergency intervention. **High-Yield:** Cherry-red spot at macula in pale retina = CRAO (vascular emergency); within 4–6 hours, use ocular massage + carbogen to attempt embolus dislodgement; always exclude GCA (ESR, temporal artery biopsy if indicated) and investigate embolic source (carotid Dopplers, cardiac imaging, ECG). [cite: AK Khurana Ophthalmology 7e; Harrison 21e Ch 32]