14.2.2: Functions of Eye Parts
Master the structure-function relationship in vision
Eye Structure & Functions
Cornea
Refracts (bends) light
Most refraction happens here! The cornea is responsible for approximately 70% of the eye's focusing power.
Iris
Controls how much light enters
Adjusts pupil size in response to light levels - dilates in dim light, constricts in bright light.
Lens
Focuses light onto the retina
Fine-tunes focus by changing shape (accommodation). Works with cornea to create sharp images.
Retina
Contains light receptors
Rods detect light intensity (black/white vision). Cones detect color. Converts light to electrical impulses.
Optic Nerve
Carries impulses to the brain
Transmits electrical signals from retina to visual cortex for image interpretation.
Cambridge IGCSE Biology 0610 - Syllabus 14.2.2
Core Learning Objectives:
- ✓ Identify the functions of cornea, iris, lens, retina, and optic nerve
- ✓ Understand that most refraction occurs at the cornea
- ✓ Explain how light is focused onto the retina
- ✓ Describe the role of the optic nerve in vision
Key Exam Points:
- • Use precise terms: "refracts" not "bends"
- • Image on retina is inverted (upside down)
- • Cornea provides most focusing power (70%)
- • Lens fine-tunes the focus
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