Structure of the Eye

Introduction

• Eyes enable us to see the world around us.
• The eye is often referred to as the "eyeball" when visualized without the skin.

Major Parts of the Eye

Iris

• Visible structure of the eye.
• Controls the eye color (via pigments).
  • Example: brown iris reflects brown light.
• Has a central hole called the pupil.
• Function: Regulates the size of the pupil to control light entry.
  • Bright light: pupil constricts to reduce light entry.
  • Low light: pupil dilates to allow more light.
  • Experiment: Pupils constrict when exposed to sudden light.

Pupil

• Central hole in the iris.
• Allows light to enter the eye.

Cornea

• Transparent front part of the eye.
• Works with the lens to focus light.

Lens

• Located behind the iris and the cornea.
• Transparent and flexible.
• Adjusts to focus light correctly on the retina.
  • This adjustment is critical for clear vision.

Aqueous Humor

• Watery liquid filling the space between the cornea and the lens.
• Function: Helps to maintain eye shape and refract light.

Retina

• Back part of the eye lined with light-sensitive cells.
• Converts light into electrical signals.
• Function: Image processing and sending electrical signals through the optic nerve to the brain.

Optic Nerve

• Connects the retina to the brain.
• Transmits electrical signals for processing.

Vitreous Humor

• Jelly-like substance between the lens and the retina.
• Function: Maintains the shape of the eye.

Ciliary Muscles

• Fiber-like structures that hold the lens in place.
• Function: Change the shape of the lens to adjust its optical power.
  • More bending needed for closer objects (higher optical power).
  • Less bending needed for distant objects (lower optical power).
  • This process is known as accommodation.

Summary

• Cornea, aqueous humor, lens: Focus light on the retina.
• Retina: Converts light into electrical signals.
• Optic Nerve: Transmits these signals to the brain.
• Vitreous Humor: Maintains the eye's shape.
• Iris: Regulates the pupil size, controlling light entry.
• Ciliary Muscles: Adjust lens curvature for focusing, enabling accommodation.