New
New
Year 10
Edexcel
Foundation

Common defects of the human eye

I can describe common defects of the eye and how we treat them.

New
New
Year 10
Edexcel
Foundation

Common defects of the human eye

I can describe common defects of the eye and how we treat them.

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Lesson details

Key learning points

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

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.

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.

The impact of concave and convex lenses on focal point can be demonstrated using a light box and lenses, as in physics, and really helps to demonstrate the corrective nature of lenses.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Match the part of the eye to its function.
An image in a quiz
Correct Answer:a,cornea

cornea

Correct Answer:b,iris

iris

Correct Answer:c,lens

lens

Correct Answer:d,ciliary muscles

ciliary muscles

Q2.
What changes the shape of the lens?
Correct answer: ciliary muscles
iris
cornea
pupil
Q3.
Starting with the light entering the eye, put the following steps in order to describe how we see.
An image in a quiz
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.
Q4.
Which part of the eye changes size to control how much light enters the eye?
Correct Answer: Iris, The iris
Q5.
Label the parts of this diagram.
An image in a quiz
Correct Answer:a,cornea

cornea

Correct Answer:b,lens

lens

Correct Answer:c,retina

retina

Q6.
Match the description of the lens to the object it is focusing on.
Correct Answer:lens is long and thin,when the ciliary muscles relax to focus on objects that are far away

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

Correct Answer:lens is short and fat,when the ciliary muscles contract to focus on objects that are near

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

Q3 Alexander_P/Shutterstock

6 Questions

Q1.
Which of the following statements describes short-sightedness?
Able to see things clearly far away, but objects close up appear blurred.
Correct answer: Able to see things clearly close up, but objects further away appear blurred.
Objects close up and also objects further away both appear blurred.
Q2.
Which of these statements are true about long-sightedness?
A concave lens can be used to correct vision.
Correct answer: A convex lens can be used to correct vision.
Correct answer: Without glasses, the focal point is past the retina.
Correct answer: Long-sightedness can occur when the lens stiffens.
Long-sightedness can occur when the eyeball is elongated.
Q3.
What part of the eye is replaced during a cataract operation?
Correct Answer: The lens, lens
Q4.
Which common eye defect is shown below?
An image in a quiz
short-sightedness
Correct answer: long-sightedness
colour blindness
cataracts
Q5.
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
Correct answer: short-sightedness
Correct answer: concave lens
convex lens
Q6.
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.
Correct answer: The sister is a carrier of red-green colour blindness.
Correct answer: The sister has normal colour vision.
The brother has normal colour vision.
Correct answer: The brother is red-green colour blind.
Q4 Alexander_P/Shutterstock