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AQA GCSE Biology · 8461
AQA 8461 · 4.5.2.3 The Eye Check the specification (PDF) (opens in a new tab)
Relate the structures of the eye (retina, optic nerve, sclera, cornea, iris, ciliary muscles, suspensory ligaments) to their functions.
Explain the process of accommodation for near and distant objects.
Describe myopia and hyperopia and how they are treated with lenses.
Interpret ray diagrams showing eye defects and corrections.
Light must be focused onto the retina, the light-sensitive layer at the back of the eye, to give a clear image. The cornea bends incoming light, while the lens changes shape to fine-tune the focus as you look between objects at different distances. This change in lens shape is called accommodation. A more curved lens bends, or refracts, light more strongly than a thinner lens.
Imagine looking at a finger held close to your face. The ciliary muscles contract, so the suspensory ligaments loosen and pull less on the lens. The lens becomes thicker and more curved. It refracts the light rays strongly, bringing them to a focus on the retina.
Now look across a room. The ciliary muscles relax, pulling the suspensory ligaments tight. The ligaments pull the lens thinner and less curved. The lens then refracts light only slightly, again bringing it to a focus on the retina. The key difference is how much the lens needs to bend the light, not where the retina is.
Changing the tension on the lens changes its shape and the amount of refraction, keeping near and distant objects in focus on the retina.
Near object: ciliary muscles contract → suspensory ligaments loosen → lens thickens and becomes more curved → light is refracted strongly onto the retina.
Distant object: ciliary muscles relax → suspensory ligaments tighten → lens is pulled thin and less curved → light is refracted only slightly onto the retina.
For each distance, link all four stages: ciliary muscles → suspensory ligaments → lens shape → amount of refraction.
Do not confuse accommodation, which changes lens shape, with the pupil reflex, which changes how much light enters the eye.
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Accommodation
The change in lens shape that focuses light from near or distant objects onto the retina.
Refraction
The bending of light as it passes between materials, such as into or out of the lens.
Ciliary muscles
A ring of muscle in the eye that contracts or relaxes to alter the tension on the lens.
Suspensory ligaments
Fibres that connect the lens to the ciliary muscles and can pull the lens thinner when taut.
Put your knowledge into practice — try past paper questions for Biology
Accommodation
The change in lens shape that focuses light from near or distant objects onto the retina.
Refraction
The bending of light as it passes between materials, such as into or out of the lens.
Ciliary muscles
A ring of muscle in the eye that contracts or relaxes to alter the tension on the lens.
Suspensory ligaments
Fibres that connect the lens to the ciliary muscles and can pull the lens thinner when taut.