# Explain how the structure of the eye allows a person to see an object that is close to them and then to see a distant object clearly.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.4 Vision and hearing · Explain · 5 marks

> The eye contains several structures that work together to focus light onto the retina. The lens and ciliary muscles play a key role in this process.

## Mark scheme (5 marks)

1. Light from a close object requires greater refraction / bending to focus on the retina
2. Ciliary muscles contract (when viewing a close object)
3. Suspensory ligaments loosen / slacken (when viewing a close object), allowing the lens to become more curved / fatter
4. For a distant object, ciliary muscles relax and suspensory ligaments pull tight, making the lens thinner / less curved
5. This process (changing lens shape) is called accommodation and ensures a focused image falls on the retina / fovea

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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