What do the numbers on eyeglasses mean?

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   I often see some numbers on eyeglasses such as +1.00, +2.50. What do these numbers mean? Does it something like the strength of your eyes? Is like 1.00 the weakest and it goes up from there?

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joan eyeglasses Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 06 Sep 2009 Online Status: Offline Posts: 77	Post Options Post Reply Quote joan eyeglasses Report Post Quote Reply Topic: What do the numbers on eyeglasses mean? Posted: 04 Feb 2010 at 1:14pm
	I often see some numbers on eyeglasses such as +1.00, +2.50. What do these numbers mean? Does it something like the strength of your eyes? Is like 1.00 the weakest and it goes up from there?

joan eyeglasses Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 06 Sep 2009 Online Status: Offline Posts: 77	Post Options Post Reply Quote joan eyeglasses Report Post Quote Reply Posted: 04 Feb 2010 at 2:39pm
	A: I have seen some information about this side. I think it can answer your question. They say the numbers in a prescription basically mean the power needed in the lens to get the light to focus on the retina to obtain clear vision! Just to put it simply: when a person is farsighted, their eyeball is too short and the light comes into focus behind the retina. To correct this, a plus (+) powered or converging lens is needed to bring the light back to focus on the retina. When a person is nearsighted, their eyeball is too long and the light focuses in front of the retina. To correct this, they need a minus (-) powered or diverging lens to bring the light into focus on the retina. The number in a person’s prescription is just the strength of lens needed to bend the light to focus on the retina. Technically 0.00 or Plano is the lowest number and has no correction. From there it goes up in quarter increments +0.25, +0.50, +0.75, +1.00 etc.... The same goes for minus prescriptions -0.25, -0.50, -0.75, -1.00 etc... And they can get pretty high like prescriptions like -18.00 exist for example! Anyways hope this helps a bit.