Elements of a Complete Eye Examination
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Regular eye care should be part of your preventative health care.
It is estimated that more than half of the U.S. population has a
vision disorder. Many of these individuals do not seek routine eye
care and remain unaware of their impairment. Routine eye care is
important since many eye diseases such as glaucoma, have no
obvious symptoms until their later stages of development. This is
when treatment becomes more difficult and damage often
irreparable.
When seeking eye care, it is helpful to know the aspects that
comprise a comprehensive exam. All parts of the exam are
important to determine the visual functioning and health of your
eyes. Described below are the key elements of a complete eye
examination.
Patient History - Information is gathered about any current
problems and past visual and ocular history. A patient's general
health, medication usage, and allergy history is also reviewed. This
is done because many health conditions such as diabetes and high
blood pressure can have an effect on your eyes. A patient's family
medical and ocular history is also important to obtain since they
reveal risk factors for developing certain eye conditions.
Visual Acuity - This measures how well a patient can see at
distance and near. A notation of 20/20 indicates normal eye
sight. If a patient is measured at 20/100, this means a person
with 20/20 sight could be 100 feet away from an object and see it
with the same clarity as a person with 20/100 could at 20 feet.
Eye Motility - This tests the ability of the eyes to move in all
directions. This provides information about how well the six
external eye muscles and the nerves that control their movement
are functioning. An impairment in movement can indicate a
neurological and/or general health problem.
Cover Test - This is a related procedure which assesses how
well the eyes stay aligned when viewing an object. This test is
performed by alternately covering each eye. Eye turns (strabismus)
are identified in this manner. This test is critical with children,
since some eye turns can result in lazy (amblyopic) eyes. If left
untreated, this can result in permanent impairment of vision.
Pupillary Responses - During this test the doctor shines a
light into your eyes in a specific pattern to evaluate the pupils'
responses. This test provides information about the neurological
pathways conducting visual information from the eye to the brain
where vision is ultimately registered.
Confrontational Visual Fields - This procedure checks
the patient's peripheral vision. Defects in the visual field can be
indicative of retinal or neurological problem.
Depth Perception - This visual ability is often evaluated
using a test that measures stereopsis, the highest form of depth
perception. In order for stereopsis to be perceived, exacting eye
alignments must be obtained with both eyes working
simultaneously. Errors in eye alignment or the suppression of
vision from either eye will result in a lack of depth seen.
Color Vision - This is performed with children to determine in
a color vision deficiency has been inherited. Males are much more
likely than females to have inherited this condition. The term color
blindness is often inaccurately used. Few patients completely lack
any color vision. Most perceive colors differently over a narrower
range in the color spectrum.
Refraction - This test determines the prescription needed to
see clearly at distance and near. It is during this test when the
degrees of various vision disorders such as nearsightedness
(myopia), farsightedness (hyperopia), astigmatism, and presbyopia
are determined. At the end of the refraction, other tests are often
conducted to evaluate a patient's focusing ability and other visual
skills.
Slit lamp viewing - The doctor will use an instrument called
a slit lamp (biomicroscope) to illuminate and magnify the
structures of a patients eyes. Eye conditions such as cataracts are
detected using this method.
Tonometry - This is to measure the pressure within the eyes.
Pressure is created by the balance between the production and
drainage of fluid out of the eye. Abnormally elevated pressure is a
risk factor for the development of glaucoma.
Dilation of the pupils - To allow for maximum visibility of
the retina and optic nerve, eye drops should be used to dilate your
pupils. The retina is examined for holes, macular degeneration,
and other abnormalities. The retina is the only structure in the
body where working blood vessels can be observed. Abnormalities
in these vessels can indicate the presence of diabetes, high blood
pressure, and other disorders. The optic nerve is examined for
signs of glaucoma and other conditions.
