Encyclopedia of Health and Medicine

86 The Eyes
See also AGING, VISION AND EYE CHANGES THAT
OCCUR WITH; ELECTRORETINOGRAPHY; NIGHT BLINDNESS;
RETINITIS PIGMENTOSA; RETINOPATHY.
diplopia The medical term for double vision, a
circumstance in which a person perceives a single
object as a two distinct images. Diplopia can be
vertical (images one above the other) or horizontal
(images beside each other). Diplopia that is
present when using both eyes and goes away
when covering one EYE is binocular; diplopia that
persists even when one eye is covered is monocular.
Each has different clinical implications.
Numerous health conditions can cause diplopia or
have diplopia among their symptoms.
Causes of
Monocular Diplopia
ASTIGMATISM
CATARACT
DRY EYE SYNDROME
KERATOCONUS
PTERYGIUM
RETINOPATHY
STRABISMUS
Causes of
Binocular Diplopia
BRAIN injury (traumatic or
STROKE)
BRAIN TUMOR
DIABETES
cranial NERVE disorders
GRAVES’S OPHTHALMOPATHY
MULTIPLE SCLEROSIS
MYASTHENIA GRAVIS
The diagnostic path begins with basic OPHTHALMIC
EXAMINATION and NEUROLOGIC EXAMINATION. The findings
of these exams determine the direction and
nature of further testing. As diplopia is a symptom
rather than a condition, treatment targets the
underlying cause. In degenerative disorders such as
MULTIPLE SCLEROSIS and MYASTHENIA GRAVIS, diplopia
may persist or worsen as the condition progresses.
For monocular diplopia, patching the affected eye
may alleviate the double image.
See also AMBLYOPIA; CRANIAL NERVES; STRABISMUS;
VISION IMPAIRMENT.
dry eye syndrome A condition in which the
lacrimal (tear) glands do not produce enough tears
or the tears evaporate too quickly, causing the EYE
to become dry and irritated. Dry eye syndrome
has numerous causes, the most common of which
are aging, medication side effects, and extended
exposure to a dry or dusty environment. People
who work in occupations that require close focus,
such as with computers or assembly-line tasks,
also may develop dry eyes as a result of insufficient
blinking. Dry eyes also may accompany
autoimmune conditions such as SYSTEMIC LUPUS
ERYTHEMATOSUS (SLE), RHEUMATOID ARTHRITIS, and
SJÖGREN’S
SYNDROME. Cigarette smoking exacerbates
dry eye syndrome.
The symptoms of dry eye syndrome include
redness, itching, and the sensation of grit in the
eyes. The diagnostic path targets identifying the
underlying cause when possible. ANTIHISTAMINE
MEDICATIONS, antihypertensive medications, ANTIDE-
PRESSANT MEDICATIONS, and medications to treat
PARKINSON’S DISEASE commonly cause dry eyes as a
SIDE EFFECT; sometimes switching to a different
medication reduces eye dryness and irritation.
Treatment is frequent use of artificial tears or
restasis drops and remedying any identifiable
cause when possible. The ophthalmologist may
treat persistent dry eye syndrome with lacrimal
plugs (also called punctal plugs), tiny segments of
acrylic that become soft and gelatinous when
inserted into the lacrimal ducts. These plugs slow
the drainage of tears from the eye. Some recent
studies suggest that increasing dietary intake of
essential fatty acids, notably linoleic and gammalinolenic
acids, improves the eye’s ability to produce
tears.
See also AGING, VISION AND EYE CHANGES THAT
OCCUR WITH; ALLERGIC CONJUNCTIVITIS; ALLERGIC RHINI-
TIS; BLEPHARITIS; CONJUNCTIVITIS.