Eyesight
Problems (Refractive Errors)Introduction: Eyesight
problems, medically termed "refractive
errors", are common. They can often develop within a few months
and they occur mostly in the early teenage years and in the mid 40's to 50's. In
the ages between 10 and 13 when the eye ball experiences a great deal of growth
and can genetically grow too long, this is often associated with myopia (nearsightedness,
runs in families ). In the mid 40's to early 50's the aging process leads to a
relative shortening of the eye ball and this is associated with hyperopia (far-sightedness). Signs
and Symptoms: With uncorrected myopia (nearsightedness) your
eyesight
would be blurred as shown in this link. Objects in front would be in focus,
but the landscape in the background is not.
Myopia
is the visual condition in which only nearby objects appear in focus, much like
a camera permanently focused at a close distance (Nearsightedness = without glasses
or optical correction only near objects, typically when held very close to the
eyes, are sighted). Nearsightedness is caused by either the eye being too long
(axial myopia) or eye having too much refractive power (refractive myopia).
With hyperopia (farsightednes), however, the patient
sees the distance clearly. In this example seen through the eyes of a
patient with farsightedness the girl up front is not in focus. Note that the background
in the distance is clear and focused. The patient has a problem reading a newspaper
and the arms feel too short to be able to focus on the print. Reading glasses
help the patient to see the print in focus again. With astigmatism
the surface
of the cornea in these patients is not like a perfect globe, but rather
like the asymmetric shape of a rugby ball. This is illustrated
in this link. The same image as shown above is not in focus in the front
or back. All of it is blurred because the cornea has different curvatures.
This link explains more about the diagnostic
tests regarding astigmaitsm. Diagnostic
Tests: The simplest test to check the overall vision is a visual
acuity test. Using eye charts the doctor or optometrist will determine
which of the letters or numbers you can still accurately read (20/20 vision is
perfect) at a certain distance. Here is another
site that explains this. Treatment: Glasses
and contact lenses are that main conventional means of correcting
visual problems such as myopia, hyperopia and astigmatism. However, there
are operative methods (refractive
surgery) that can now be used, although they have their strengths
and weaknesses. It is tempting to throw away glasses and contact lenses and have
clear vision after refractive surgery (so the commercial goes). But there are
possible complications, such as a certain percentage of cataract and glaucoma
formation following these surgeries and a weakening of the cornea making the eye
more susceptible for rupture with physical trauma. If you would like to explore
refractive surgeries, discuss this with the eye surgeon carefully and weigh the
pros and cons. For my part I decided to continue to live with glasses.
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