**Core Concept**
The question is testing the student's knowledge of a congenital anomaly affecting the optic nerve, specifically a pit that forms in the optic disc. This pit can lead to various complications, including retinal detachment and secondary glaucoma.

**Why the Correct Answer is Right**
A congenital pit in the optic nerve, also known as an optic disc pit, is a rare congenital anomaly that occurs due to a defect in the closure of the embryonic fissure during fetal development. This pit can communicate with the subarachnoid space, leading to the potential leakage of cerebrospinal fluid (CSF) into the vitreous humor. As a result, the vitreous humor can become hypotonic, leading to retinal detachment and secondary glaucoma.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not related to the congenital anomaly described in the question.
* **Option B:** This option is incorrect because it does not accurately describe the cause of a congenital pit in the optic nerve.
* **Option C:** This option is incorrect because it is a different congenital anomaly affecting the eye.

**Clinical Pearl / High-Yield Fact**
It is essential for ophthalmologists and neuro-ophthalmologists to recognize and manage congenital pits in the optic nerve early on to prevent complications such as retinal detachment and secondary glaucoma.

**Correct Answer: D. Optic disc pit.**