Common defects of the human eye | Biology | Quizalize & Oak National Academy

Starter quiz

Match the part of the eye to its function.

a

⇔

cornea ✓

b

⇔

iris ✓

c

⇔

lens ✓

d

⇔

ciliary muscles ✓
What changes the shape of the lens?

ciliary muscles ✓

iris

cornea

pupil
Starting with the light entering the eye, put the following steps in order to describe how we see.

1

⇔

Light enters the eye.

2

⇔

Light is refracted by the cornea.

3

⇔

Light is focused by the lens.

4

⇔

Light is sensed by the retina.
Which part of the eye changes size to control how much light enters the eye?

'Iris' ✓
Label the parts of this diagram.

a

⇔

cornea ✓

b

⇔

lens ✓

c

⇔

retina ✓
Match the description of the lens to the object it is focusing on.

lens is long and thin

⇔

when the ciliary muscles relax to focus on objects that are far away ✓

lens is short and fat

⇔

when the ciliary muscles contract to focus on objects that are near ✓

Exit quiz

Which of the following statements describes short-sightedness?

Able to see things clearly far away, but objects close up appear blurred.

Able to see things clearly close up, but objects further away appear blurred. ✓

Objects close up and also objects further away both appear blurred.
Which of these statements are true about long-sightedness?

A concave lens can be used to correct vision.

A convex lens can be used to correct vision. ✓

Without glasses, the focal point is past the retina. ✓

Long-sightedness can occur when the lens stiffens. ✓

Long-sightedness can occur when the eyeball is elongated.
What part of the eye is replaced during a cataract operation?

'The lens' ✓
Which common eye defect is shown below?

short-sightedness

long-sightedness ✓

colour blindness

cataracts
A patient has an elongated eyeball. Select the condition they are most likely to have and the type of lens that could be used to correct the defect.

long-sightedness

short-sightedness ✓

concave lens ✓

convex lens
Two siblings are tested for the red-green colour blindness gene. The sister's phenotype is Rr and the brother's phenotype is r. Which of the following statements are correct about the siblings?

The sister is red-green colour blind.

The sister is a carrier of red-green colour blindness. ✓

The sister has normal colour vision. ✓

The brother has normal colour vision.

The brother is red-green colour blind. ✓

Worksheet

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Presentation

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Video

Lesson Details

Key learning points

Common defects of the eye (e.g. cataracts, short- and long-sightedness) and how they impair vision.
How common defects of the eye can be treated.
Interpretation of ray diagrams to explain how common eye defects affect vision, and the effects of corrective lenses.
How colour blindness occurs and its impact on vision.

Common misconception

Mistakes with the defects and treatments in vision caused by long- and short-sightedness (e.g. getting the symptoms or the type of lenses mixed up) or how lenses actually correct vision are common.

The conditions are dealt with separately with clear and concise information conveyed and supported with diagrams and reinforced with questions that focus on these mistakes and misconceptions.

Keywords

Lens - An object that can focus light rays. In the eye, it brings light rays to focus on the retina.
Retina - The back of the eye which senses light brightness and colour.
Focus - The process of bringing light rays together to converge at a single point creating a clear image.
Refraction - Occurs when light travels from one transparent medium to another, causing a change in direction.