**Core Concept**
Central Retinal Venous Occlusion (CRVO) and ocular ischemic syndrome due to carotid artery stenosis are two distinct conditions affecting the eye. CRVO occurs when there is a blockage in the central retinal vein, leading to increased venous pressure and subsequent retinal edema. In contrast, ocular ischemic syndrome is caused by reduced blood flow to the eye due to carotid artery stenosis, resulting in retinal ischemia.

**Why the Correct Answer is Right**
Dilated retinal veins are a characteristic feature of CRVO, resulting from the increased venous pressure. In ocular ischemic syndrome, retinal veins may be normal or even decreased in caliber due to decreased blood flow. This is because the primary issue in ocular ischemic syndrome is the reduction in arterial blood flow, rather than increased venous pressure. The presence of dilated retinal veins would suggest CRVO rather than ocular ischemic syndrome.

**Why Each Wrong Option is Incorrect**
**Option B:** Tortuous retinal veins can be seen in both CRVO and ocular ischemic syndrome, as the increased venous pressure in CRVO and the decreased blood flow in ocular ischemic syndrome can both cause venous tortuosity.

**Option C:** Retinal artery pressure is typically decreased in ocular ischemic syndrome due to reduced blood flow, whereas it may be normal or even increased in CRVO due to the increased venous pressure.

**Option D:** Ophthalmodynamometry measures the pressure in the ophthalmic artery and can be used to diagnose carotid artery stenosis, which is a cause of ocular ischemic syndrome. It can help differentiate between CRVO and ocular ischemic syndrome.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with retinal vein occlusion, it's essential to consider both central retinal vein occlusion and ocular ischemic syndrome in the differential diagnosis. The presence of dilated retinal veins, particularly in the context of other risk factors such as hypertension and atherosclerosis, should raise suspicion for CRVO.

**✓ Correct Answer: A. Dilated retinal vein**