Lecture on the Anatomy of the Eye

Overview of the Eye's Structure

• The eye has multiple layers and chambers.
• Fibrous Tunic: The outermost layer, primarily composed of collagen fibers.
  • Sclera: The white part, providing structure and resistance to stretching.
  • Cornea: Transparent front part, allowing light entry and is highly regenerative.

Vascular Tunic

• Rich in blood supply and pigmentation.
• Choroid:
  • Pigmented to limit light reflection.
  • Contains blood vessels supporting the eye.
• Ciliary Body:
  • Controls the lens's thickness, aiding in focusing images from varying distances.
  • Uses muscles and suspensory ligaments to change lens shape.
• Iris:
  • Regulates pupil size through muscles:
    • Sphincter pupillary muscle for constriction.
    • Dilator pupillary muscle for dilation (sympathetic reaction).

Retina and Photoreception

• Retina: The innermost layer, where light is converted to electrical impulses.
  • Contains photoreceptors (rods and cones) for vision.
  • Pigmented areas reduce light scattering.
• Photoreceptor Function:
  • Light hits photoreceptors, causing nerve impulses to the brain.

Chambers and Humors

• Vitreous Humor:
  • Located in the posterior chamber, maintains eye shape and pressure.
• Aqueous Humor:
  • Fills the anterior chamber, provides nutrients to eye components.
  • Secreted by the ciliary epithelium, exits via the canal of Schlemm.
  • Maintains intraocular pressure; imbalance can cause glaucoma.

Eye Movement

• Eye Muscles:
  • Six muscles control eye movement.
  • Four rectus muscles move the eye up, down, medially, and laterally.
  • Two oblique muscles for rotational movements.
• Superior Oblique: Passes through a pulley (trochlea) near the nose.
• Inferior Oblique: Arises from the lower orbital rim.

Detailed Retina Anatomy

• Consists of three neuron layers:
  • Rods and Cones: Initial photoreceptors.
  • Bipolar Cells: Intermediate transmission.
  • Ganglion Cells: Form the optic nerve.
• Rhodopsin Molecule: Key in light perception.
  • Retinol part changes shape when exposed to light, initiating the vision process.