How does the prescription of Eye Glasses range?

-7 is stronger than -6.5

The minus means you are short sighted, and a positive number means you are long sighted. The optician told me it goes as high as 20, but the worst eyesight shes ever heard of, was -13!

To have perfect vision would be 0 in each eye, not 20 20 vision, as is commonly accepted.

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A contact lens prescription includes the following: power, base curve, diameter and brand. The power can be calculated from your spectacle power but you don't have the other information. You could guess at the rest. If you are in the US or Western Europe, you can't legally be sold contacts without a prescription that includes all of the above. You may find someone that will though. Results would range from lenses that work great to serious damage to your eyes. You should be fit in contact lenses with additional measurements being taken and someone who knows what they are doning looking at the lenses on your eyes under high magnification.

The farther from 0 (zero) the prescription is, the stronger it is.

My old prescription was -8.25 and -7.75...which means that I couldn't see worth a darn lol and your prescription is less strong than mine was.

Myopia = negative numbers -0.25 to -15 (yes, I have seen this before)

Hyperopia = positive numbers +0.25 to +7...that's the highest I personally have seen for hyperopic correction, but I'm sure it can go stronger.

It doesn't exactly follow the same rule as counting, but if you think about it 0 is 20/20 vision without any glasses or contacts...the further you get from that point, the worse your vision...hence the stronger your prescription.

Eyeglass lenses are measured very similarly to a numberline being numbered with both Plus and Minus numbers, most of the time in quarter steps. -7.00 is stronger in the minus direction than a -6.75. put 0 in the middle as being plano or having to correction. You can then number your minus numbers on one side and your plus ones on the other. We do not use the words positive or negative in this part of optics. we use positive and negative to describe frame form. Strength its self depends on what direction you go in. Usually we say it is stronger if it has a bigger number. It is like measuring money. If you are -$7.50 in your bank that is more than being -6.25, considering you would be further in debt.. But it is better to have +3.00 than a +2.00 in the bank, becuase that is more money! Does this help to understand it? I know it is confusing. I still get confused and I do this every day!

The RX scale goes in quarters, both negative and positive. "-" means that you are nearsighted (or can only see up close), "+" means that you are far sighted (or can only see far away).

If your eyes are -6.5, the next stronger RX would be -6.75 and so forth.

The closer you get to "0" on the scale, the less of a RX strength you have. The - and the + are basically opposites.

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as an aside, -25.00 is the most myopia i've personally ever seen, and +17.00 the most hyperopia.

i have seen probably 7-10 people over +15.00, but they were literally all aphakes (post cataract extraction w/o implant). the most farsightedness i've ever seen in the absence of cataract extraction was +10.00

It goes upwards. For example -7.0 is stronger than -6.5, and in the other direction, my prescription of -.75 is weaker than your -6.5.

The higher that negative number, the worse your vision is. My eyes are a -5.25 in both. Your vision is worse than mine.

-7 is definitely stronger. the higher you go the stronger.

and for farsightedness I am not quite sure (when you have a positive power)