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CATARACTS
What
are cataracts?
Cataracts
are changes in the lens of the eye that decrease its ability
to transmit light and to deliver a clear image to the retina.
They can occur alone or as a secondary consequence of other
eye problems or diseases such as retinitis pigmentosa, ocular
contusion, smoking, diabetes, injury, complications of eye
surgery, or systematic use of steroids. Cataracts are usually
identified by their location in the lens, or by their general
cause. The major types of cataract identified by their origin
or appearance during development are:
- Congenital
/ Infantile: present in the first year of life
- Secondary:
caused by an eye disease
- Traumatic:
caused by an injury
- Senile:
occur in later adult life.
The
most common type of cataracts are senile cataracts. They
develop in 75% of people over 65 years of age and in 95%
of those over 85 years of age.
How
do cataracts affect vision?
By
scattering and reducing the light reaching the retina, cataracts
reduce image luminance and contrast. Some common symptoms
of cataract include a reduction in acuity, night vision,
light sensitivity, and color discrimination, especially
for blues. Blurring and yellowing of vision, and increased
sensitivity to glare are also common. During old age the
hardening of the lens associated with cataract can induce
myopia, allowing an eldery observer to regain the ability
to read up close. This phenomenon is called second
sight.
The
photos below simulate the possible effects of a cataract
on vision. Notice the decreased illumination, acuity,
and color saturation in the view through a cataract compared
to the view without a cataract.
 
Treatment
Surgery
is the only treatment for cataracts. Nowadays, cataract
is usually treated using the technique of phacoemulsification,
in which the lens is broken up using an ultrasonic vibrating
probe (40Hz) and aspirated through a small incision at the
margin of the eye. A small, plastic intraocular lens (IOL)
is then inseted into the eye to replace the refractive power
lost by the removal of the lens. Some cataract patients
experience blurry vision after surgery due to scar tissue
that results from the surgery. For most, however, cataract
surgery is highly effective. About 95% of post-operative
patients have excellent vision, with improved acuity, color
discrimination, and sensitivity in low light.
The link that follows (with permission of the author), provides more detailed information on cataracts, cataract surgery and cataract care:
Information on Cataracts
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Cassatt
| Cézanne | Degas
| El Greco | Monet
| Rembrandt
| Renoir | Van
Gogh
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