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how bad is my eye prescription?

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(eye prescription) Are my eyes bad?
Today I went to my eye doctor for a check up
and I received an eye prescription that says:

Sphere _____________ Cylinder _______________ Axis
OD -2.25 _____________ -3.25 ________________160
OS -2.75 ______________ -3.00__________________ 20

Are my eyes bad, and I do not understand what OD, OS, Sphere, Cylinder and Axis mean on this prescription....

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asked Feb 12 in Health by smyadmin

3 Answers

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You are nearsighted and have astigmatism. O.D. is your right eye, O.S. is your left eye. Sphere is the correction for nearsightedness and cylinder corrects for astigmatism.

Astigmatism is an irregular curvature of the eye--its less round and shaped more like a football (its very common). Astigmatism causes you to see things somewhat distorted. You know that weird curving you get in new glasses--that is the correction for astigmatism. You see walls as curved but your brain nows that's not possible so it tries to straighten it out for you. Then when you get glasses to correct for astigmatism your brain is still compensating and you see that curved affect until your eyes adjust to the correction. Axis is the degree of your astigmatism is set at (180 is the highest).

And yes your eyes are somewhat bad. Sorry. Anything above a -3.00 in sphere is starting to get up there. And anything above a -1.00 is considered high for astigmatism.

To make things simpler when referring to your prescription you would add the sphere and cylinder powers together to get what is known as total power. Total power for your right eye is -5.50 and your left is -5.75. you can just round off even further and just say you total power is about -5.50 when talking about your prescription.

One more thing, you would say your prescription its "minus five fifty, total power" rather than "negative five point fifty." (positive and negative is for math not optics)

But while your prescription is a bit up there, it isn't until minus 8 or 9 or higher that its considered really bad. Prescriptions of minus 15 or 20 are very rare.

answered Feb 12 by doorhingeorange
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How bad is a -4.00 eye prescription?
I had my eye exam today and that's what my optometrist filled out on the sheet for new lenses. I was wondering if that was really bad (poor vision). I am nearsighted. Also, can someone give me that in the Snellen fraction?
answered Feb 12 by shery
This prescription would be what I would call moderate in amount. Don't get me wrong. With this amount of nearsightedness you definitely have significant vision clarity issues, but I have patients in my practice with -15.00 and more. More than you actual prescription is involved in what your resultant visual acuity is but I would estimate you would have somewhere around 20/400 visual acuity.
Me. I am an optometric physician.
When light rays pass through a lens, one that is thick in the center and thin on the outside, the central light ray goes straight through, undeviated. The light rays away from the center are bent, and they all cross that central light ray some distance away from the lens. That distance is called the focal distance and the more powerful the lens, the closer the focal point is to the lens itself.

The formula for this is P=1/d where d is in meters.

So a lens that focuses light 1 meter away would be a +1.00 lens.
A lens that focused light a half meter away would be a +2.00 lens.
third of a meter away, +3.00.
Quarter of a meter, +4.00
tenth of a meter, +10.00.

your eyes are too powerful. They are +4.00 too powerful, so you need a -4.00 lens to "neutralize" the power of your eye's lens system which is made up of your cornea (the clear part in the front through which you can see the blue or brown or green or hazel, or gray or ? part) and the lens itself.

So you can see a quarter of a meter in front of you really well, just beyond that, not so good.

Once you've corrected your too powerful eyes by moving your focal distance out to infinity, your vision should be 20/20 which is 'normal'. It does no good to say the camera takes lousy pictures if you don't bother to focus it.

The Snellen equivalent would be how well you see compared to 'normal' which would be less at 20 feet because you aren't focused at twenty feet, you are focused at about 10 inches or about a quarter of a meter (a meter being 39.something something inches).

If you can only see the 400 foot letter, you are 20/400. One is a measure of the optical power, the other a measure of the seeing power of your eye, assuming you don't have anything else 'wrong' with your eye such as a cataract, hemorrhage, nerve disease, macula disease, vascular disease, leaking, drying.....
yawn.... I know, I know...

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