What is the world's largest fish?
The harmless whale shark holds the title of largest fish, with the record being a 59 footer captured in Thailand in 1919.
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- Nearsightedness farsightedness and how glasses work
Nearsightedness farsightedness and how glasses work
Simply put, the eyeglass lens is a tool you use to focus light appropriately on your retina. For example, a lens that is concave, or curves inward, is used to correct nearsightedness, while a lens that is convex, or curves outward, is used to correct farsightedness.
Nearsightedness causes nearby objects to appear clear, while objects farther away look blurry. Farsightedness is where far away objects appear clear and objects up close appear blurry.
To correct astigmatism, which is caused by distortions in the shape of the cornea, a cylinder shaped lens is frequently used.
Reference: http://my.webmd.com/content/article/63/71988.htm?z=4051_00000_7000_to_07
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