I am 19 years old. Ive just been to the opticians and got a prescription saying both my eyes were + 0.50 Sph with nothing else written down. She said I will need glasses. Do I really need them? I have always been a little bit long sighted but was never told I need glasses. And has spending a lot of time on the computer without enough breaks contributed to needing glasses? COmputer work does hurt my eyes now. Also, what is my eye sight? is it 20/20 or better? She said I had very good distance sight.
Well, from what I was told by my doctor this is what it means:
The eye 2 eye Guide to your Prescription
In this section of our site, we are going to attempt to explain a little more about your prescription, so that you can have a better idea about the prescription your optician has given you. So here it is, the Eye 2 Eye Guide to Your Prescription: The Eye Sight Examination: The Written Prescription
Examples Step One Step Two Step Three
Sph Power Cyl Power Axis Prism Base
The Eye Examination
To understand the prescription, you firstly need to understand a little more about the actual eye examination, and the processes the optician uses to reach the prescription, without blinding you with the science.
A sight examination is a very complicated process, and the opticians primary objective is to check that your eyes are healthy, so while conducting the test, the optician is always checking for numerous symptoms and physical anomalies within the eye, that can indicate numerous problems (some related to your vision like glaucoma or cataracts, and some which are not directly related to the eye, but which can be detected during the test, like diabetes or highblood pressure).However, in this explanation, we are going to skip over these health checks, as they are can be quite technical and difficult to explain.
Find your actual prescription can be simplified and explained in three steps, so that is what we will attempt to do here.
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The first step.
After sitting you down and asking you a few questions, the optician will usually examine your eyes with an instrument called an opthalmascope. This is the hand held instrument that shines a light into your eyes. This is the first and primary step in finding your prescription.
The optician uses the opthalmascope to check for various eye conditions and the health of the eye as described above, but he also uses this instrument to initially assess your prescription.
The opthalmascope is a very clever device with a series of adjustable lenses. The optician looks through the opthalmascope and adjusts the internal lenses within the opthalmascope until he can bring the back of your eye into focus. In order to do this the optician has too use the opthalmascope to "compensate" for any focal imperfections within the eye.
The image that the optician is looking at is the back of your eye, and if it is out of focus, the optician is simply using the opthalmascope to bring it back into focus. The lens power within the opthalmascope that he must use to do this gives him a general idea of the prescription required to correct your vision.
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The Second Step.
The second step involves the reading chart. This is when the optician asks you to read letters from the chart, one eye at a time. There is a very good reason for this. When you use both eyes together, the human brain is very good at compensating for your prescription, so for example if one eye is better at seeing things at a close distance and the other eye prefers thing further away, your brain will usually compensate by using the best eye for the job.
The optician will ask you to read from the chart, one eye at a time, and then he will place lenses in front of your eyes, and ask you whether your vision seems better or worse. Although the optician already has a good idea of your prescription, he has to make sure that his initial tests are accurate. When the optician is satisfied that you can see accurately through each eye with the prescription he has found, he will move on to step three.
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The Third Step.
Now that the optician know the exact prescription for each eye, he will test both eyes at once. Again there is a very good reason for this. The optician knows that just because he has put the exact clinically perfect prescription in front of a patients eyes, the patient may not be able to cope with that exact prescription.
As your prescription has slowly changed, your brain has told the muscles within the eye to stretch and flex to compensate for these changes, and simply putting these lenses in front of the eye, will not necessarily stop this compensation. This can cause problems for the patient, so the optician will take into account your previous prescription, and may choose to modify the prescription slightly - in order to prevent possible adaption problems.
The optician will test both eyes using lenses and the chart, and when he is happy that these adaption problems will not occur, or will only be mild, he will reach his final prescription, usually advising you that the prescription will take a few days to get used to.
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The written prescription.
Below are a few typical prescriptions, with links so that you can understand what it means.
Below are some examples of typical prescriptions
Example 1: A typical long sighted prescription with a slight astigmatism
Base Right +1.00 +0.50 180
Left +0.75 +0.25 175
Example 2: (the same prescription as example one, but written in a slightly different format)
Base Right +1.50 -0.50 90
Left +1.00 -0.25 85
Example 3 :A Short sighted Prescription (note the right eye has an astigmatism, the left does not)
Base Right -0.75
Example 4: A prescription with prismatic power in one eye
Base Right +2.75
UP Left -0.50
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The Sphere power of your prescription, is used to measure the power in your lens, which compensates for short-sightedness (Myopia) or long-sightedness (Hyperopia).
If the power has a (-) sign next to it, then you are short sighted
If the power has a (+) sign after it, then you are long sighted
Explaining the power itself, again become a little complicated, it is sufficient to say that this power starts at 0.00, which means that no power is required, and it increases in increments of 0.25, so the higher the figure, the stronger the lens.
A + or - 50 is not bad, it's a bit past 20/20 like maybe 20/25. You could use glasses if the computer hurts your eyes because you may be sitting to close if you are farsighted. Computers cause eyestrain without having bad eyesight so rule of thumb is to look away from a computer screen at least once every thirty minutes and concentrate on something that is far off and wait about 5 minutes. This just keeps the tension out of your eyes and will help with the pain of using a computer. Sit back farther away from the monitor if you are farsighted ... closer if nearsighted but never closer than three feet get glasses, the computer monitor gives off a low amount of something that isn't good for any of us ... don't ask me what it is but I have been told depending on the type of monitor you are using such as LCD or whatever there could be something that isn't good for you that emits from the screen. I am not a doctor or anything just what those who work with computers have told me.
Thank you LeMeBe. Thanks for the explaination of sight and the advice. Do you think wearing glasses would prevent my sight from getting worse? Because Im not struggling at the moment, except from aching eyes from loads of computer work. P.s I have a LCD screen! Interesting!
Yes, your friend has a point in my opinion. I would recommend getting an opinion from an Ophthalmologist and resting your eyes more/breaks from the computer.
Years ago, I saw an Optician at a popular glasses/lenses place in the USA and I was pushed into buying a pair of glasses. Well, I started wearing them all the time and began to have headaches. I finally decided to see an Ophthalmologist and he told me there was NO need for glasses and basically wasted money on them. He stated I was so slightly near-sighted that he would not recommend correcting it at that time.
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