Defects of the Eye Flashcards
All 7 cards in this deck
What causes short-sightedness and where does the light focus?
The eyeball is too long or the cornea/lens too curved, so light focuses in front of the retina and distant objects look blurred.
What causes long-sightedness and where does the light focus?
The eyeball is too short or the lens too thin/not curved enough, so light focuses behind the retina and near objects look blurred.
True or false? Long-sightedness is corrected with a concave lens.
False. Long-sightedness needs a convex (converging) lens; a concave (diverging) lens corrects short-sightedness.
What is a cataract and how does it affect vision?
A build-up of protein makes the lens cloudy, so light is dispersed and vision is blurred/cloudy.
How are cataracts treated?
Surgery to replace the cloudy lens with an artificial (plastic) lens.
What causes colour blindness?
Cone cells in the retina are missing or not working (usually red–green cones), so certain colours cannot be distinguished.
What are the steps to plan an investigation to test a hypothesis about eyesight?
e.g. 'People with brown eyes are more likely to be short-sighted than people with blue eyes'
- Choose equal numbers of people in each group: equal numbers with brown eyes and with blue eyes.
- Test each person's vision in the same way: use an optician's eye chart at a set distance.
- Compare the results: if more brown-eyed people are short-sighted, the hypothesis is supported.