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 Light
rays enter the eye from distant objects along parallel lines. When
they reach the eye they are bent, or refracted, by the cornea. These
rays of light are refracted even further by the crystalline lens
and are sharply focused on the retina at the back of the eye.
Hyperopia
Hyperopia or farsightedness is a type of focusing problem in which
the eye has insufficient refracting power. Individuals with hyperopia
typically find it easier to see distant objects than it is to see
near objects. This is commonly due to the eye being too short in
length, or the cornea being too flat. In the hyperopic eye, light
that enters the eye comes to focus behind the retina. For clear
vision, light must be focused precisely on the retina, so for hyperopic
eyes, convex lenses are used to add the extra convergence necessary
to focus light on the retina.
Myopia
Myopia usually appears before the age of 20 and is generally considered
a hereditary condition. In myopia, or nearsightedness, the eyeball
is elongated and the cornea cannot properly focus the light coming
into the eye.
In mild cases of myopia, the patient may need correction for only
some activities, such as driving. In this situation, prescription
glasses or sunglasses are usually the best and most convenient solution.
When the problem is more serious and correction is needed most of
the waking hours, many patients choose contact lenses. If contact
lenses are used, eyeglasses will also be required for use when contact
lenses are not practical. For those who simply do not want to wear
eyeglasses or contact lenses, LASIK surgery may be available. It’s
important to visit your eye doctor and discuss all options before
making a decision.
Symptoms of myopia include needing to squint to make out distant
objects, headaches, feelings of fatigue or eyestrain. Patients who
continue to have these symptoms even when they're using prescription
products to correct their myopia may need further correction.
A complete vision and eye-health examination is necessary to diagnose
myopia and determine the best correction. Often, a myopic patient
doesn't realize that he or she has a vision problem because the
nearsightedness affects the eyes so gradually. That's why having
regular a eye exam is so crucial.
Astigmatism
Astigmatism is a refractive error where the focusing power is not
uniform in all directions. This results in a range of focal points
entering the eye. Astigmatism can cause blurred and/or strained
vision for both distant or near tasks. Since the ideal is a single
focal point at the retina, people with astigmatism are corrected
with toric lenses designed to create a single point focus. Astigmatism
is a common condition and it is often found in association with
myopia or hyperopia.
Presbyopia
Presbyopia is a visual condition that usually occurs around age
40 or 45. As we age, the crystalline lens gradually becomes less
flexible. Since the lens focuses by changing its shape, reduced
flexibility results in strain and fatigue with reading and other
near tasks. Proper correction for Presbyopia include reading glasses,
bifocals, trifocals, or today's preferred progressive lenses. Progressive
lenses provide distance, intermediate, near vision, as well as everything
in between for the most natural vision possible.
Strabismus
Strabismus is a misalignment of the two eyes. It is the abnormal
turning of one eye either inward or outward. If the turning is inward,
the condition is called esotropia, if the turning is outward, it
is called exotropia. Strabismus occurs in 2-3% of the population.
Strabismus may be managed by some combination of spectacle lenses,
surgery, and orthoptics.
Amblyopia
Amblyopia or "lazy eye" is a condition where an apparently
healthy eye is not capable of seeing as clearly as its fellow eye.
This condition occurs at an early age in an individual who because
of Strabismus or unequal refractive error is unable to use the two
eyes together. During the "critical period", a time when
the neurological pathways are developing, amblyopia can set-in if
the eyes are not used together. Treatment of amblyopia requires
some combination of spectacles, patching, and orthoptics and is
initiated at an early age, typically before seven.
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