A Middle aged man brought to casualty with unilateral headache, right eye congested and painful, with sudden vision loss. The diagnosis is
**Core Concept**
The patient's presentation suggests an acute ocular condition involving the eye and surrounding structures, likely involving vascular or inflammatory processes.
**Why the Correct Answer is Right**
The patient's symptoms of unilateral headache, congested and painful right eye, and sudden vision loss are classic signs of a **central retinal artery occlusion (CRAO)**. CRAO occurs when the central retinal artery, which supplies blood to the retina, becomes blocked, leading to ischemia and infarction of the retinal tissue. This condition is a medical emergency and requires prompt treatment to preserve vision.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because a **cluster headache** typically presents with severe unilateral orbital pain, but without the associated vision loss.
**Option B:** This is incorrect because a **migraine** can cause unilateral headache and visual disturbances, but the symptoms are usually less severe and not accompanied by sudden vision loss.
**Option C:** This is incorrect because a **corneal abrasion** typically presents with eye pain and blurred vision due to a superficial corneal injury, but without the associated headache or sudden vision loss.
**Clinical Pearl / High-Yield Fact**
In cases of suspected CRAO, prompt ophthalmologic evaluation and treatment, such as intravenous tissue plasminogen activator (tPA) or retinal laser photocoagulation, are crucial to preserve vision.
**Correct Answer: C. Central Retinal Artery Occlusion**