**Core Concept**
The Apex National Institute of Ophthalmology refers to a premier national-level ophthalmology institute in India that provides advanced training, research, and clinical services in eye care. It is a key institution recognized for its role in shaping ophthalmic education and practice in the country.

**Why the Correct Answer is Right**
The Dr. R P Centre for Ophthalmic Sciences in Delhi is officially recognized as one of the apex national institutes of ophthalmology in India. It is a leading center for postgraduate education, research, and clinical training in ophthalmology, established under the Department of Ophthalmology, Ministry of Health & Family Welfare. The center is known for its high-quality training programs and is a recognized authority in Indian ophthalmology.

**Why Each Wrong Option is Incorrect**
Option A: Advance Eye Care PGI Chandigarh is a major eye hospital but is not designated as an "apex national institute."
Option B: RIO (Rajiv Gandhi Institute of Ophthalmology) is a well-known eye hospital but not classified as a national apex institute.
Option D: Shankara Netralaya is a prominent private eye care center in Chennai and does not hold the status of a national apex institute.

**Clinical Pearl / High-Yield Fact**
In India, the Dr. R P Centre for Ophthalmic Sciences, Delhi, is the only institution officially designated as an "apex national institute" for ophthalmology under the national framework, making it essential for postgraduate training and research in the field.

✓ Correct Answer: C. Dr. R P Centre for Ophthalmic Sciences , Delhi