Overview
This lecture explains the process of accommodation in the human eye—how the lens changes shape to focus on near and distant objects—detailing the roles of the ciliary muscle, suspensory ligaments, and lens.
Structure and Function of the Eye in Accommodation
- The lens is the only part of the eye that can change shape to focus images.
- Light entering the eye is bent (refracted) by the lens to form a clear image on the retina.
- The ciliary muscle surrounds the lens and controls its shape via the suspensory ligaments.
- Suspensory ligaments connect the ciliary muscle to the lens, holding it in place.
Accommodation for Distant Vision (6 meters or more)
- Ciliary muscle relaxes.
- Suspensory ligaments become taut (pull tight).
- Lens becomes thinner and flatter.
- Less refraction occurs (less bending of light).
- A clear image is focused on the retina.
Accommodation for Near Vision (less than 6 meters)
- Ciliary muscle contracts.
- Suspensory ligaments slacken (become loose).
- Lens becomes fatter and more convex (bulges outward).
- More refraction occurs (more bending of light).
- A clear image is focused on the retina.
Key Terms & Definitions
- Accommodation — the process by which the lens changes shape to focus on near or distant objects.
- Lens — transparent structure in the eye that bends (refracts) light to focus images on the retina.
- Refraction — bending of light as it passes through the lens.
- Ciliary muscle — a ring of muscle around the lens that changes its shape for focusing.
- Suspensory ligaments — fibers that connect the ciliary muscle to the lens, holding it in place.
- Convex — curved outward, describes the lens shape during near vision.
Action Items / Next Steps
- Review the structure and function of the ciliary muscle, suspensory ligaments, and lens.
- Memorize the step-by-step process of accommodation for near and distant vision.
- Learn key terms for use in exam answers.
- Prepare flashcards for vocabulary revision.