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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