GCSE Biology revision

The eye (biology only)

The human nervous system

AQA 4.1.1.1

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Identify and describe What Is Accommodation?, Key Structures Involved and Focusing on Near Objects in the context of the eye (biology only).

MOST 🎯🎯

Explain the relationships between What Is Accommodation?, Key Structures Involved and Focusing on Near Objects and how they contribute to the eye (biology only).

SOME 🎯🎯🎯

Apply and analyse knowledge of What Is Accommodation?, Key Structures Involved and Focusing on Near Objects to interpret unfamiliar information about the eye (biology only).

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

What Is Accommodation?

Accommodation is a reflex that changes the refractive power of the lens so that both near and distant objects can be focused clearly onto the retina
The cornea and lens both refract (bend) light, but the cornea always refracts by the same amount, so it is the lens that fine-tunes focus
Light must always converge precisely on the fovea, a specific spot on the retina, for a sharp image to be formed

1. What Is Accommodation?AQA

Notes

Accommodation is a reflex that changes the refractive power of the lens so that both near and distant objects can be focused clearly onto the retina
The cornea and lens both refract (bend) light, but the cornea always refracts by the same amount, so it is the lens that fine-tunes focus
Light must always converge precisely on the fovea, a specific spot on the retina, for a sharp image to be formed

Key Structures Involved

The ciliary muscle is a ring-shaped muscle that surrounds the lens and controls its shape
The suspensory ligaments connect the lens to the ciliary muscle and either pull the lens taut or allow it to slacken
The suspensory ligaments are not muscles, so they cannot contract or relax — they can only be pulled taut or slackened by the ciliary muscle

2. Key Structures InvolvedAQA

Notes

The ciliary muscle is a ring-shaped muscle that surrounds the lens and controls its shape
The suspensory ligaments connect the lens to the ciliary muscle and either pull the lens taut or allow it to slacken
The suspensory ligaments are not muscles, so they cannot contract or relax — they can only be pulled taut or slackened by the ciliary muscle

Focusing on Near Objects

Light from nearby objects strikes the eye at a wide angle and must be refracted a great deal to focus on the fovea
To increase refractive power, the lens needs to become short and fat, making its surface more curved
The ciliary muscle contracts inwards towards the lens, causing the suspensory ligaments to slacken and allowing the lens to return to its naturally fatter shape

3. Focusing on Near ObjectsAQA

Notes

Light from nearby objects strikes the eye at a wide angle and must be refracted a great deal to focus on the fovea
To increase refractive power, the lens needs to become short and fat, making its surface more curved
The ciliary muscle contracts inwards towards the lens, causing the suspensory ligaments to slacken and allowing the lens to return to its naturally fatter shape

Focusing on Distant Objects

Light from distant objects arrives as almost parallel rays and requires much less refraction to focus on the fovea
To reduce refractive power, the lens must be stretched out so its surface is less curved
The ciliary muscle relaxes and moves away from the lens, pulling the suspensory ligaments taut and stretching the lens into a thinner, flatter shape

4. Focusing on Distant ObjectsAQA

Notes

Light from distant objects arrives as almost parallel rays and requires much less refraction to focus on the fovea
To reduce refractive power, the lens must be stretched out so its surface is less curved
The ciliary muscle relaxes and moves away from the lens, pulling the suspensory ligaments taut and stretching the lens into a thinner, flatter shape

Comparing Near and Distant Focus

When switching between near and distant objects, the ciliary muscle and suspensory ligaments work together to continuously alter the shape of the lens
A key point to remember is that when the ciliary muscle contracts, it moves inwards towards the lens, not outwards
The shape change of the lens directly controls how strongly it refracts light, ensuring the image always falls on the fovea

5. Comparing Near and Distant FocusAQA

Notes

When switching between near and distant objects, the ciliary muscle and suspensory ligaments work together to continuously alter the shape of the lens
A key point to remember is that when the ciliary muscle contracts, it moves inwards towards the lens, not outwards
The shape change of the lens directly controls how strongly it refracts light, ensuring the image always falls on the fovea

Long-Sightedness (Hyperopia)

Long-sightedness, or hyperopia, occurs when the lens cannot refract light enough, meaning nearby objects appear blurry
In a long-sighted eye, the image of a near object would theoretically form behind the retina rather than on it
Convex (converging) lenses in glasses provide extra refracting power, helping the eye focus light correctly onto the retina

6. Long-Sightedness (Hyperopia)AQA

Notes

Long-sightedness, or hyperopia, occurs when the lens cannot refract light enough, meaning nearby objects appear blurry
In a long-sighted eye, the image of a near object would theoretically form behind the retina rather than on it
Convex (converging) lenses in glasses provide extra refracting power, helping the eye focus light correctly onto the retina

Short-Sightedness (Myopia)

Short-sightedness, or myopia, occurs when the lens refracts light too much, meaning distant objects appear blurry
In a short-sighted eye, light from distant objects is over-refracted and focuses in front of the retina rather than on it
Concave (diverging) lenses in glasses spread light rays outwards before they enter the eye, counteracting the over-refraction so the image falls correctly on the retina

7. Short-Sightedness (Myopia)AQA

Notes

Short-sightedness, or myopia, occurs when the lens refracts light too much, meaning distant objects appear blurry
In a short-sighted eye, light from distant objects is over-refracted and focuses in front of the retina rather than on it
Concave (diverging) lenses in glasses spread light rays outwards before they enter the eye, counteracting the over-refraction so the image falls correctly on the retina

Corrective Lenses at a Glance

Convex lenses are used to correct hyperopia (long-sightedness) by converging light rays before they enter the eye
Concave lenses are used to correct myopia (short-sightedness) by diverging light rays before they enter the eye
The type of corrective lens needed depends entirely on whether the eye's lens is refracting too little or too much

8. Corrective Lenses at a GlanceAQA

Notes

Convex lenses are used to correct hyperopia (long-sightedness) by converging light rays before they enter the eye
Concave lenses are used to correct myopia (short-sightedness) by diverging light rays before they enter the eye
The type of corrective lens needed depends entirely on whether the eye's lens is refracting too little or too much

Key Terminology Summary

Accommodation is the automatic adjustment of the lens's shape to maintain a focused image on the fovea
Hyperopia is the medical term for long-sightedness, where near objects cannot be focused clearly
Myopia is the medical term for short-sightedness, where distant objects cannot be focused clearly