Overview
This lecture explains the concept of accommodation in the eye, focusing on how the lens changes its shape to help us focus on objects at different distances.
Anatomy of the Eye in Accommodation
- Only the lens can change shape to focus images; the cornea and retina shapes remain constant.
- The lens bends (refracts) light to focus it on the retina at the back of the eye.
- Suspensory ligaments hold the lens in place and connect to the ciliary muscle, forming a system that changes lens shape.
Accommodation for Distant Vision
- Distant vision refers to focusing on objects 6 meters or more away.
- The ciliary muscle relaxes.
- Suspensory ligaments become taut (pull tight).
- The lens becomes thinner and flatter.
- Less refraction occurs, allowing clear images to form on the retina.
Accommodation for Near Vision
- Near vision refers to focusing on objects less than 6 meters away.
- The ciliary muscle contracts and becomes thicker.
- Suspensory ligaments slacken (become loose).
- The lens becomes fatter and more convex (bulging).
- More refraction occurs, so a clear image forms on the retina.
Key Terms & Definitions
- Accommodation — the process where the lens changes shape to focus on near or distant objects.
- Lens — a flexible structure that bends light to focus images on the retina.
- Refraction — the bending of light as it passes through the lens.
- Ciliary Muscle — a ring of muscle around the lens controlling suspensory ligaments.
- Suspensory Ligaments — fibers connecting the ciliary muscle to the lens and holding the lens in place.
- Convex — a shape that curves outward; describes the lens when focusing on near objects.
Action Items / Next Steps
- Review diagrams of the eye and label the lens, ciliary muscle, and suspensory ligaments.
- Prepare flashcards for key terms and definitions.
- Practice explaining the process of accommodation for both near and distant vision.