Biological termModerate1 mark
2(i)
Name the following:
A defect in our eyes, in which some parts of the object are in focus while the other parts are blurred.
Topic: Astigmatism
Previous-year question practice database
Answer
Exam answer
ASTIGMATISM.
Explanation
Astigmatism is caused by an IRREGULAR CURVATURE of the cornea or lens. Because the surface is unevenly curved, light in one plane focuses at a different point from light in another, so part of the image is sharp while part is blurred AT THE SAME TIME.
That simultaneous sharp-and-blurred quality is exactly what the question describes, and it distinguishes astigmatism from the other defects, which blur the WHOLE image: MYOPIA — distant objects blurred; concave lens HYPERMETROPIA — near objects blurred; convex lens ASTIGMATISM — part of the image blurred at any distance; CYLINDRICAL lens
The key words are "some parts... while the other parts".
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