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What can cause focussing problems as children grow? As adults age?

As children grow different parts of the eye can change shape. At an adult's age it makes it more difficult to focus on objects that are close.

Explain why a person who is near- sighted can see a nearby object clearly, but not a distant one?

A person who is near-sighted can see a close object clearly, but not a distant one because the lens converge the rays in front of the retina. Before they strike the retina, the rays have spread out and have formed a blurry image.

Explain why a person who is far-sighted can see a distant object clearly, but not a close one?

A person who is far-sighted can see a distant object clearly, but not a close one because the eye has a shorter shape than a normal one so, the lens forms the image behind the retina, and the image becomes fuzzy.

How does an irregularly-shaped cornea cause astigmatism?

An irregularly-shaped cornea causes astigmatism because it focuses the image on more than one point on the retina, resulting in blurred vision.

What are three examples of what a person who is blind might be able to see?

1)see clearly in a small part of the scene
2)see from edges of their eyes not from their centre
3)can detect light or darkness around them

Why are children in developing countries at a greater risk of becoming blind?

They are at a greater risk because they have lack of malnutrition in poor countries, because they can't afford certain things.

How can snow blindness be prevented?

It can be prevented by using close-fitting glasses.

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