**Question:** Oldest component of lens of the eye is

A. Capsule
B. Nuclear matter
C. Parietal layer
D. Fibre layer

**Correct Answer:** D. Fibre layer

**Core Concept:** The lens of the eye is composed of two main layers: the cortex and the nucleus. These layers together form the lens's fibre cells, which are responsible for its transparency and power to focus light.

**Why the Correct Answer is Right:** The fibre layer (option D) is the oldest component of the lens, as it is formed during the lens's development in fetal life. This layer is responsible for maintaining the lens's transparency and its ability to focus light. The lens's nuclear matter (option B) is the innermost part of the lens and is composed of denser, older cells.

**Why Each Wrong Option is Incorrect:**

A. Capsule (option A) is the outermost layer of the lens, composed of elastic fibers called zonules that hold the lens in place and allow it to change shape for focusing. The capsule is not considered the oldest component.

C. Parietal layer (option C) is the outermost part of the lens and is composed of the capsule and zonules, providing structural support and holding the lens in place. The parietal layer is not the oldest component.

**Clinical Pearl:** The lens's transparency and accommodation ability are crucial for maintaining visual acuity. Any disruption to these functions can lead to conditions like cataracts or presbyopia.

**Explanation:** The lens is a transparent, biconvex structure that plays a vital role in refraction and accommodation, allowing the eye to focus light on the retina. The fibre layer, composed of mature cells, is the oldest part of the lens, while the capsule and parietal layer provide structural support and hold the lens in place.

**Why the Correct Answer is Right:**

The lens of the eye, consisting of the nucleus (oldest component) and cortex (younger component), is essential for maintaining optical clarity and accommodating power. The fibre layer (option D) is the innermost part of the lens, formed during fetal life, and is composed of mature cells that contribute to the lens's transparency and ability to change shape.

**Why Each Wrong Option is Incorrect:**

A. Capsule (option A) is the outermost layer of the lens and serves as a support structure, anchoring the lens to the ciliary body. The capsule is not considered the oldest component.

C. Parietal layer (option C) is the outermost part of the lens, composed of the capsule and zonules, which provide structural support and hold the lens in place. The parietal layer is not the oldest component.