vision at a distance (myopia).
vision of nearby objects and difficulty reading, possibly
causing eyestrain and headaches (hyperopia).
degrees of blurriness in portions of the visual field (astigmatism).
When To Call Your Doctor
an appointment with an ophthalmologist or optometrist if
you have vision problems.
What Are They?
Refractive disorderswhich include myopia
(nearsightedness), hyperopia (farsightedness), and astigmatismare
common, correctable vision problems. Light enters the eye through
the cornea, the thin, transparent membrane covering the eye,
and then the pupil, the dark area in the center of the iris.
The lens, located behind the pupil, focuses the light rays onto
the retina, the layer of light-sensitive cells that line the
back of the eye. Refractive disorders arise when irregularities
in the shape or refractive strength of these structures distort
the focus and impair vision.
In myopia, objects at a distance appear out of
focus; in hyperopia, nearby objects are unclear. In astigmatism,
the cornea is unevenly curved, producing blurriness or varying
degrees of distortion in portions of the visual field. Astigmatism
may be combined with either myopia or hyperopia in the same eye.
In addition, the lens becomes progressively less flexible after
age 40, impairing close vision. Refractive disorders may be corrected
with glasses, contact lenses, or laser surgery.
What Causes Them?
factors play a role.
to popular belief, vision cannot be improved by refusing to wear
glasses if you need them or by performing so-called eye exercises.
ophthalmologist will perform an eye examination and determine
your eyeglass measurement.
How to Treat Them
or contact lenses are prescribed to correct vision. The prescription
is updated as vision changes.
types of laser surgery have been developed to sharpen vision:
PRK (photorefractive keratectomy) and LASIK (laser-assisted in-situ
keratomileusis). They use a special machine known as an excimer
laser to produce pulses of light energy that can alter the shape
of the cornea so that light rays from distant objects will focus
on the retina with greater precision. Both procedures can be
performed to correct myopia, hyperopia, astigmatism, and presbyopia.
An older form of surgery, known as radial keratotomy (RK), which
helps correct mild to moderate myopia, is now used infrequently.
goggles to protect your eyes or a sports strap to secure glasses
during sports and strenuous activities.
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