**Question:** True about Optic disc – a) Horizontal diameter 1.76 mm, b) Vertical diameter 1.88 mm, c) Contain 1 million nerve fibers, d) Central retinal artery directly supplies this area

**Core Concept:** The optic disc (also known as the optic nerve head) is a crucial part of the human eye involved in vision and the visual pathway. It is the location where the optic nerve, which carries visual information from the retina to the brain, exits the eye. The optic disc plays a vital role in vision and understanding its anatomy and function is essential for medical students studying ophthalmology and neurology.

**Why the Correct Answer is Right:**

a) The horizontal diameter of the optic disc is approximately 1.76 mm, which is a key measurement in assessing the health of the optic nerve and overall eye health. The optic disc serves as the exit point for the optic nerve and is a crucial structure for vision.

b) The vertical diameter of the optic disc is approximately 1.88 mm. Both diameters are important for understanding the overall size and structure of the optic disc, as well as any potential abnormalities or changes in these dimensions that may indicate optic nerve damage or other eye conditions.

c) The optic disc contains around 1 million nerve fibers. These nerve fibers are part of the optic nerve, which transmits visual information from the retina to the brain. Understanding the number of nerve fibers in the optic disc is essential for assessing the health and integrity of the optic nerve and the visual pathway.

d) The central retinal artery directly supplies the optic disc. This artery carries oxygenated blood to the optic nerve, ensuring its proper functioning and maintaining vision. Understanding the blood supply to the optic disc is crucial for recognizing potential vascular diseases affecting the eye and vision.

**Why Each Wrong Option is Incorrect:**

a) Option A is incorrect because the actual horizontal diameter is approximately 1.76 mm, not 2.5 mm as stated. This measurement helps in assessing the health of the optic nerve and the eye.

b) Option B is incorrect because the vertical diameter is approximately 1.88 mm, not 2.3 mm. Understanding the size of the optic disc is essential for identifying potential abnormalities related to its dimensions, which may indicate optic nerve damage or other eye conditions.

c) Option C is incorrect because the optic disc contains around 1 million nerve fibers, not 2 million as stated. The number of nerve fibers in the optic disc is vital for assessing the health and integrity of the optic nerve and the visual pathway.

d) Option D is incorrect because the central retinal artery directly supplies the optic disc, not the optic nerve head as stated. Understanding the blood supply to the optic disc is crucial for recognizing potential vascular diseases affecting the eye and vision.

**Clinical Pearls:**

1. **Core Concept:** The optic disc, also known as the optic nerve head, is a crucial part of the eye responsible for transmitting visual information from the retina to the brain. It is the site at which