**Core Concept**
Congenital blindness in children is often due to genetic or developmental abnormalities affecting the eye or visual pathway. The most common causes involve issues with the optic nerve, retina, or cornea.

**Why the Correct Answer is Right**
The most common cause of congenital blindness in children is **Congenital Cataract**. A cataract is a clouding of the lens in the eye that can occur before birth or during early childhood. This can lead to impaired vision or even total blindness if left untreated. The lens in the eye plays a crucial role in focusing light onto the retina, and a cataract can block this process. Congenital cataracts are often caused by genetic mutations or maternal infections during pregnancy.

**Why Each Wrong Option is Incorrect**
**Option A:** **Retinopathy of Prematurity (ROP)** is a condition that affects premature infants and can cause blindness, but it is not the most common cause of congenital blindness in children.
**Option B:** **Glaucoma** is a group of eye conditions that can damage the optic nerve and lead to vision loss, but it is not the most common cause of congenital blindness in children.
**Option C:** **Retinal Detachment** is a condition where the retina separates from the back of the eye, but it is not a common cause of congenital blindness in children.

**Clinical Pearl / High-Yield Fact**
It's essential for pediatricians and ophthalmologists to perform regular eye exams on children to detect congenital cataracts and other vision problems early on, as early treatment can significantly improve visual outcomes.

**Correct Answer:** A. Congenital Cataract.