The eyeball consists of a round tough white skin called

1. Analyze the question

The question asks for the specific name of the outer, tough, white layer of the human eyeball. This is a common biology/physics (optics) question regarding the structure of the eye.

2. Explain the concept

The human eye is composed of three main layers:

• The Sclera (Sclerotic layer): This is the outermost, tough, white, fibrous layer. Its primary function is to protect the inner parts of the eye and maintain the shape of the eyeball.
• The Choroid: This is the middle layer, which is rich in blood vessels and contains dark pigments to prevent internal reflection of light.
• The Retina: This is the innermost layer where light-sensitive cells (rods and cones) are located, acting as the screen where images are formed.

3. Show the solution

• Option A (Sclerotic): This refers to the sclera. It is the tough, white, outer coat of the eye. This matches the description in the question.
• Option B (Choroid coat): This is the vascular middle layer, not the tough white outer skin.
• Option C (Optical fiber): This is a technology used for transmitting light signals, not a part of the human eye.
• Option D (Accommodation): This is the process by which the eye changes its focal length to focus on objects at different distances; it is a function, not a physical layer of the eye.

4. Identify the answer

Based on the anatomical structure of the eye, the tough white outer skin is the Sclerotic layer (or Sclera).

5. Tip

To remember the layers of the eye from outside to inside, use the mnemonic "SCR":

• Sclera (Tough, white outer layer)
• Choroid (Middle, blood-rich layer)
• Retina (Inner, light-sensitive layer)