Hi yellowdandelion,
The following is the result of my research for the questions you have
asked. This was an interesting subject for me, as I was a contact lens
wearer for many years (I had -3.75 and -4.50) before I had the Lasik
operation done.
Glasses and contact lens prescriptions are measured in diopters which
is the measurement of the optical power of the lens.
“The prescription is usually written with a sphere and a cylinder.
"The sphere (round, not shaped like a football) numbers can range from
+15 to over –30. However, most patients are from +6.00 to –6.00.
Cylinder measures the amount of astigmatism and can range up to 6
diopters or more. Cylinder can be written in a plus or minus cylinder
format...
...A positive number indicates hyperopia (farsightedness) and a
negative number, myopia (nearsightedness). The larger the diopters
value (positive or negative), the greater the refractive error.”
SVC
http://www.sharpervisioncenters.com/lasercorrection.asp
“How to read and understand a glasses or contact prescription.
Glasses prescriptions are not difficult to understand. First of all,
the right eye is usually listed first, and is noted by O.D. The left
eye is O.S. The prescription has mainly three parts: the sphere, the
cylinder and axis, and the add. The sphere determines nearsightedness
or farsightedness. No sphere is noted as "plano". If the power is a
minus, it is a nearsighted prescription. If it is a plus, it is
farsighted. Mild prescriptions are in the range of plus or minus 1 to
3, while high prescriptions are over plus or minus 5 to 7…”
“…Contact lens prescriptions are similar to glasses prescriptions.
However, they also state the name and type of contact lens being used,
any tint in the lens, the base curve of the lens, and the diameter.”
DirectLens: OPTICS AND VISION TESTS
http://www.directlens.com/education.htm#prescription
“Myopia occurs when the eyeball is too long or the cornea is too
curved so light entering your eye cannot focus correctly.
If you have myopia, your cornea and lens have too much focusing power,
bending light rays to meet at a point in front of the retina. Glasses
and contacts compensate for this condition by subtracting power from
the eye's natural focus and allowing light rays to focus further back
on the retina. If you have myopia, your prescription will be negative,
for example, -4.25 diopters.
Glasses and contact lenses correct refractive errors by adding or
subtracting focusing power to your cornea and lens. The power needed
to focus images directly on your retina is measured in diopters. This
measurement is also known as your eyeglass prescription.”
Care For Your Eyes
http://www.careforyoureyes.com/article744-181.html#What%20is%20myopia?
A prescription for glasses forms the basis for a contact lens fitting.
If you look at your prescription it will be in a format similar to one
of these;
R. -3.00DS
L. -3.50DS
This indicates that you are myopia (shortsighted) of moderate degree.
Powers can range from -0.25DS to well in excess of -20.00DS. An
average power for the myopic population would be about -3.00DS (DS
signifies Diopters Sphere).
Degrees of Myopia:
Mild Myopia
<-3.00 diopters
Moderate Myopia
-3.00 to -6.00 diopters
Severe Myopia
-6.00 to -9.00 diopters
Extreme Myopia
>-9.00 diopters
Some interesting reading:
ContactLens
http://www.contactlens.co.uk/education/public/spectacle_vs_contact_lens_rx.htm
AAPOS: 20/20 Vision
http://med-aapos.bu.edu/publicinfo/store4/20.20vision8.48PM.html
LPF: 20Something
http://www.lpf.com/source/rk/20something.html
RichmondEye
http://www.richmondeye.com/symoptic.htm
Triad Publishing Co: Myopia
http://www.triadpublishing.com/eyecarereports/myopia-book.htm
To clarify, you are nearsighted which makes it difficult to focus on
distant objects, although near objects can usually be seen clearly.
The degree of your myopia, or nearsightedness, is -5.75 diopters in
the right eye and -6.50 diopters in the left eye, with 0 being the
normal.
Search criteria:
myopia OR nearsightedness measuring
myopia measuring degrees
myopia measuring degrees diopters
glasses OR “contact lens” prescriptions
I hope the information I have provided is helpful. If you have any
questions regarding my answer please don’t hesitate to ask before
rating.
Best regards,
rainbow-ga |
