Myopia, also known as nearsightedness, is inherited and is often
discovered in childhood. Myopia is a refractive error, which
results from a disorder rather than from disease. A refractive
error means that the shape of your eye does not bend light
correctly, resulting in a blurred image. As light enters the eye,
the visual image comes to a focus in front of the retina, resulting
in a defective, blurred or distorted view of distant objects.
Myopia often progesses throughout the teenage years, when the body
is growing rapidly. People with high myopia have a higher risk of
detached retina, which can be repaired with surgery, and
Hyperopia, also known as farsightedness, is usually inherited.
Children are often hyperopic which may lessen as an adult.
Hyperopia is a refractive error, which results from a disorder
rather than from disease. A refractive error means that the shape
of your eye does not bend light correctly, resulting in a blurred
image. As light enters the eye, the visual image focuses behind the
retina resulting in a defective, blurred or distorted view of both
close and distant objects.
Astigmatism usually occurs when the front surface of the eye, the
cornea, has an irregular curvature. This irregular shape results in
two focal points of light, instead of one. The simple act of
reading often creates headaches and eyestrain, since the image is
never completely clear. The individual may have to re-read the word
several times. Astigmatism often occurs with nearsightedness and
farsightedness. Astigmatism is not a disease nor does it mean that
you have "bad eyes." It simply means that you have a variation or
disturbance in the shape of your cornea.
Presbyopia is a condition in which the focusing ability of a
person's eyes has decreased to the point where vision at his
reading distance becomes blurred and difficult. The focusing lens
becomes unable to change shape and focus on close objects. This
results in blurred vision at a reading distance, as well as
eyestrain. Presbyopia most often develops in people in their
Amblyopia, sometimes called a "lazy eye," occurs when one eye does
not develop normal sight during early childhood. When one eye
develops good vision but the other does not, the eye with decreased
vision is called amblyopic. Usually, only one eye is affected by
amblyopia. This common condition should be corrected during infancy
or early childhood to obtain 3-dimensional vision and prevent
permanent vision loss.
Amblyopia has three major causes: strabismus, unequal focus, and
cloudiness in the eye.
Strabismus (misaligned eyes) is the most common form of amblyopia.
The brain "turns off" the image from the crossed eye to avoid
double vision and the child uses only the better eye.
Unequal Focus (refractive error) is an eye condition that can be
corrected by wearing glasses. Amblyopia occurs when one eye is out
of focus because it is more nearsighted, farsighted or astigmatic
than the other, all conditions that can be corrected with glasses.
The brain "turns off" the image from the unfocused eye, although
both eyes can look normal to the observer. This is the most
difficult type of amblyopia to detect and requires careful vision
measurements by an eye doctor.
Cloudiness in Normally Clear Eye Tissue may lead to amblyopia. Any
disorder that prevents a clear image from being focused inside the
eye, for example, a cataract or cloudy lens inside the eye or a
cloudy cornea at the front of the eye, can lead to the development
of amblyopia in a child. This is often the most severe form of
It is not easy to recognize amblyopia. A child may not be aware of
having one strong eye and one weak eye. Unless the child has a
misaligned eye, or other obvious abnormality, there is often no way
for parents to tell that something is wrong. However, it is
difficult to measure vision in young children. Your optometrist is
trained to estimate visual acuity in an infant by watching how well
a baby follows an object with one eye when the other eye is
covered. He or she will also carefully examine the interior of the
eye to see if other eye disorders such a tumor or an inflammatory
process inside the eye may be causing decreased vision.