The deficiencies of the eye: Long and Short Sightedness

1. Done By: Zhang Zhenglin (31) 2A4 The deficiencies of the eye:Long and Short Sightedness

2. General Information • The human eye is like a pair of converging lens • When a person looks at something, light rays from the object pass into the eye through your cornea ,through the lens that focuses the light rays and to the retina (image location) at the back of the eye

3. General Information • In a healthy eye the lens and cornea focus the light rays on a small area of your retina so that you can see the object clearly.

4. Long Sightedness

5. Definition • Far sightedness, is the state of images focusing behind the retina instead of being focused on it • This causes objects that are near to the person to seem blur • Distant objects do not look as blurred as the light rays do not need as much focusing power

6. Causes • A common cause of long-sightedness is ageing • As we age, the lens in our eyes start to change at the age of 40 and are completed by the time we are 60

7. Causes • Long sightedness also often occur in children • This may be due to inheritance, from parents to child + =

8. Causes • Also, if one has a job that requires one to do close up work, the chances of developing long sightedness

9. Solutions (Through lens) • Long sightedness can be corrected with convex corrective lenses such as spectacles or contact lenses. • These visual aids help to focus the light rays entering the eye onto the retina

10. Short Sightedness

11. Definition • Short sightedness, also commonly known as myopia, is the state of images focusing in front the retina instead of being focused on it • This causes objects that are far to the person to seem blur • Close up objects look clear, because the light rays enters the eye at a slight angle

13. Causes • Far images look blur because the eyeball has become longer • Myopia often runs in families • If one parent is short-sighted, there is a one in three chance the child will be short sighted • If both parents are short- sighted, there is a one in two chance the child will be short sighted

14. Causes • This may also be due to the person doing too much near work for prolonged periods of time • E.g. Reading, using the computer

15. Causes • Whether one has myopia also depends on ethnic background • E.g. around eight in every 10 people of Asian origin are short sighted, whereas only three in every 10 people of European origin are

16. Solutions (Through lens) • Short sighted can be corrected with concave corrective lenses such as in spectacles or contact lenses • These visual aids help to better focus the light entering the eye

17. References

18. Bupa's Health Information Team (2010, June). Long-sightedness. Bupa. Retrieved June 28, 2012, from http://www.bupa.co.uk/individuals/health-information/directory/l/long-sightedness • Bupa's Health Information Team (2010, June). Short-sightedness. Bupa. Retrieved June 28, 2012, from http://www.bupa.co.uk/individuals/health-information/directory/s/myopia • Singapore National Eye Centre (2010). HYPEROPIA. Singapore National Eye Centre SingHealth. Retrieved June 28, 2012, from http://www.snec.com.sg/eye-conditions-and-treatments/common-eye-conditions-and-procedures/Pages/hyperopia.aspx

19. Singapore National Eye Centre (2010). MYOPIA (SHORT-SIGHTEDNESS OR NEAR-SIGHTEDNESS). Singapore National Eye Centre SingHealth. Retrieved June 28, 2012, from http://www.snec.com.sg/eye-conditions-and-treatments/common-eye-conditions-and-procedures/Pages/myopia.aspx

20. Thank you!