**Core Concept**
Painful loss of vision is a symptom often associated with various ocular and orbital conditions. The underlying cause of painful vision loss is typically related to inflammation or infection affecting the eye.

**Why the Correct Answer is Right**
The correct answer involves a condition where the intraocular pressure increases due to a blockage in the drainage of aqueous humor, leading to corneal edema and pain. This condition is known as **Acute Angle-Closure Glaucoma (AACG)**. AACG occurs when the iris suddenly blocks the drainage angle, causing a rapid increase in intraocular pressure (IOP). This increase in IOP leads to corneal edema, pain, and vision loss.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not typically associated with painful vision loss. **Optic Neuritis** is an inflammatory condition that affects the optic nerve, but it usually presents with pain on eye movement, not painful vision loss.
* **Option B:** **Central Retinal Vein Occlusion (CRVO)** is a condition that affects the retinal veins, leading to vision loss, but it is not typically painful.
* **Option C:** **Open-Angle Glaucoma** is a chronic condition where the drainage angle is open, and intraocular pressure increases gradually over time. It is not typically associated with painful vision loss.

**Clinical Pearl / High-Yield Fact**
A key factor to remember is that **painful vision loss is a red flag symptom** that requires immediate medical attention. Conditions like AACG can lead to permanent vision loss if not treated promptly.

**Correct Answer: C. Open-Angle Glaucoma**