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Common eye problems in students
|By completing this chapter, you will learn the following list of topics：|
Nearsightedness, farsightedness and astigmatism are the types of refractive errors among school children in Hong Kong.
Nearsightedness (Myopia) Video
|Nearsightedness is the commonest refractive errors, and affecting around 40% of primary school children in Hong Kong.Fan et al, IOVS 2004|
|Hong Kong has one of the highest prevalence of myopia in the world. Our prevalence was three times that of the United States, more than 10 times that reported from the Middle East, and near twice that in South America. Fan et al, IOVS 2004|
|Heredity||Reading in Dim Light||Excessive Nearsighted Work|
|While the exact cause of nearsightedness remains unknown, it is believed that an interaction of heredity and environment may play a role. It tends to run in families. Environmental factors such as reading in dim light or doing excessive amount of nearsighted work may contribute to nearsightedness.|
A common sign of nearsightedness is difficulty with the clarity of distant objects like a movie, TV screen or the chalkboard in school. Nearsightedness can be corrected by spectacles with concave lens.
|Farsightedness (Hyperopia) is a condition of the eye where the light that comes in focus behind the retina. This occurs if eyeball is too short or the cornea has too little curvature, so light entering your eye is not focused correctly, causing difficulty focusing on near objects, and in extreme cases causing difficulty to focus on objects at any distance.|
Farsightedness (Hyperopia) Video
Common signs of farsightedness include difficulty in concentrating and maintaining a clear focus on near objects, eye strain, fatigue and/or headaches after close work, aching or burning eyes, irritability or nervousness after sustained concentration. Farsightedness can be corrected by spectacles with convex lens.
Farsightedness can be corrected by spectacles with convex lens.
Astigmatism is a condition where the light comes into the eye but do not focus on a single point of the retina. It is caused by the irregular shape of the cornea or sometimes the unequal curvature of the lens inside the eye. An irregular shaped cornea or lens prevents light from focusing properly on the retina, and thus, the vision becomes blurred at any distance.
Astigmatism is a very common vision condition. Most people have some degree of astigmatism. Slight amounts of astigmatism usually do not affect vision and do not require treatment. However, larger amounts cause distorted or blurred vision, eye discomfort and headaches. Astigmatism can be corrected by spectacles with cylindrical lens.
Congratulation! You have completed Chapter 3. You should now be able to distinguish the three types of refractive errors.