A 27-yr male presents with a sudden, painless loss of vision. His ocular and systemic history is unremarkable. The most likely diagnosis is:
**Core Concept**
The sudden, painless loss of vision in a young individual is likely due to an ischemic event affecting the retina. This condition is often associated with a blockage of a retinal artery, which leads to ischemia and subsequent cell death.
**Why the Correct Answer is Right**
The most likely diagnosis in this scenario is central retinal artery occlusion (CRAO). CRAO occurs when there is a blockage of the central retinal artery, which supplies blood to the retina. This blockage can be due to an embolus, thrombosis, or vasospasm. The blockage leads to ischemia of the inner retinal layers, resulting in sudden, painless loss of vision. The patient's age and the absence of any systemic or ocular risk factors make CRAO a more likely diagnosis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Ischemic optic neuropathy typically presents with pain and is often associated with systemic conditions such as diabetes, hypertension, or atherosclerosis.
* **Option B:** Retinal detachment is a condition where the retina separates from the underlying tissue, often presenting with sudden flashes of light, floaters, and a curtain of darkness.
* **Option C:** Optic neuritis is an inflammation of the optic nerve, often presenting with pain on eye movement, decreased vision, and color vision defects.
**Clinical Pearl / High-Yield Fact**
CRAO is a medical emergency and requires prompt treatment to restore blood flow to the retina and prevent permanent vision loss. The treatment options include intravenous thrombolysis, anticoagulation, and corticosteroids.
**Correct Answer: C. Central retinal artery occlusion.**