The Eye: Structure, Function and Vision Defects — AQA GCSE Biology (Separate)
The eye is a sense organ that detects light. This topic covers its structure and common vision defects.
Structure of the eye
| Part | Function |
|---|---|
| Cornea | transparent front; refracts (bends) light |
| Iris | controls how much light enters (pupil size) |
| Pupil | the gap that light passes through |
| Lens | focuses light onto the retina (can change shape) |
| Retina | contains light receptors (rods and cones) |
| Optic nerve | carries impulses to the brain |
| Ciliary muscles & suspensory ligaments | change the shape of the lens |
Vision defects
- Myopia (short-sightedness) — distant objects look blurred because light is focused in front of the retina. Corrected with a concave (diverging) lens.
- Hyperopia (long-sightedness) — near objects look blurred because light is focused behind the retina. Corrected with a convex (converging) lens.
Treating defects
As well as spectacle lenses, defects can be treated with contact lenses, laser eye surgery (changing the cornea's shape) and replacement lens surgery.
Exam tips
- Learn each eye part and its function.
- Myopia = short-sighted, light focuses in front of retina, needs a concave lens.
- Hyperopia = long-sighted, light focuses behind the retina, needs a convex lens.
- Know the modern treatments (contact lenses, laser surgery, lens replacement).