Hi ratan,
I've broken the information here into sections for you. The short
answer to your question is that the only way to tell the difference
between an improper prescription and the adaptive phase of new eye
glasses is by the duration of the symptoms. The actual symptoms are
the same: discomfort, blurry vision, headaches, squinting, etc.
ADJUSTING TO REGULAR GLASSES
Normally, one week’s time should be adequate for the eyes to feel
comfortable with new glasses or a new prescription. If discomfort
continues beyond this time, re-visit your vision specialist for
corrections.
http://www.help4srs.com/health/vision1.htm
ADJUSTING TO PROGRESSIVE LENSES
There are four factors that determine success in multifocal
[progressive] adaptation:
Brand of Multifocal
Multifocal measurement and pupillary distance
Frame measurement .
Patient motivation
http://www.youreyesite.com/bifocal.htm
"There is a short adaptation period when you are fitted with your
first pair of progressive lenses, which can range from a few minutes
to a few days. People with certain types of corrections, including
strong plus (also called strong farsighted or high hyperopic)
prescriptions, tend to have more difficulty adapting to progressive
lenses."
http://www.allaboutvision.com/lenses/progressives.htm
"Progressive lenses may take some time to get used to. It may take a
week or maybe longer to adapt for a first time wearer. The problem is
really not because it is a progressive bifocal(for the first time
wearer) but the lack of seeing at a distance through the bottom half
of the lenses."
http://www.angelfire.com/ky2/jlsumme/
HOW TO ADAPT TO PROGRESSIVE LENSES
http://www.essilor.com.sg/Consumer/Tips&Tricks/lensadapt.htm
SYMPTOMS WHICH MAY REQUIRE A NEW PRESCRIPTION
If You Have Difficulty Adjusting to Your New Glasses:
"After a few days of using your new glasses, you should be comfortable
with them. If you aren't comfortable after wearing them for two weeks,
it is possible that an error has been made. "
"Most difficulties with eyeglasses can be traced to positioning
problems or to dispensing errors. If your new eyeglasses create
discomfort or give you blurred vision or double vision, take them back
to the optical dispenser who made them. "
http://www.eyecareforyou.com/ECFYEyeglassPresc.htm
WHY IT'S DIFFICULT TO ADAPT TO PROGRESSIVE AND BIFOCAL LENSES
"When you put on glasses, the size of your visual world changes
(getting bigger or smaller depending on whether you are farsighted or
nearsighted), and your brain has to recalculate the ratio between the
amount of head movement and the amount of eye movement. This is why
sometimes you might have trouble adjusting to new glasses.
With progressives, gradual change in optical magnification occurs as
you look from the middle of the lens to the reading area. This means
that your brain must change the VOR ratio constantly as you look up
and down through the lens. This extra work is not fun for an already
overloaded brain. In addition, the progressives have zones of
distortion in the lower corners of the lenses; the distortions make
the brain work even harder.
Many people also have significant troubles with bifocal contact lenses
because these lenses project multiple images (different images for
different distances) on the retina of the eye, and the brain must sort
out which image to use. This takes practice and a fair amount of brain
power, which many people with vestibular disorders cannot spare. "
http://www.vestibular.org/eyeglasses.html
SYMPTOMS OF VISION PROBLEMS
http://www.kellogg.umich.edu/conditions/refractive/myopia.html
http://www.kellogg.umich.edu/conditions/refractive/hyperopia.html
I hope this help you out. The key in determining the difference
between adjustment discomfort and an actual error in prescription
appears to be a matter of time, not of particular symptoms.
Headaches, blurry vision and other symptoms appear in both cases.
If there is anything here that isn't clear, please feel free to ask
for clarification.
-K~
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