health of the EYEand vision, and detect problems
with the structures and functions of the eye. The
standard ophthalmic examination includes several
components. For certain parts of the examination
the ophthalmologist may place drops in the eyes
that anesthetize the eye and dilate the pupils, to
facilitate examining the structures of the back of
the eye such as the RETINAand optic disk. Some
people experience mild stinging when the drops
first enter the eye. There is otherwise no discom-
fort with an ophthalmic examination. The com-
plete exam takes about 10 minutes.
Physical ExaminationThe ophthalmologist begins with an examination
of the orbital tissues, outer eyelids, inner eyelids,
and conjunctiva (membrane lining the inner eye-
lids) of first one eye and then the other, checking
to see that the eyelids open and close properly and
looking for any growths or irritation. The ophthal-
mologist then checks the movement of the eyes,
typically by asking the person to follow the track
of an object such as a pen. Using a small light, the
ophthalmologist checks the reaction of the pupils.
These procedures help the ophthalmologist to
assess the basic neurologic aspects of the eye’s
functions.
Visual Acuity and Visual Field
The familiar SNELLEN CHARTtest for VISUAL ACUITY
features lines of letters in differing sizes and order
of presentation. Covering first one eye and then
the other, the person reads the line with the
smallest letters that appear clear. The ophthalmol-
ogist records the result as a ratio that represents
actual visual acuity compared to a standard of
20/20, with a score of 20/20 being what the nor-
mal eye sees at a distance of 20 feet. Diminished
visual acuity may result from REFRACTIVE ERRORS
such as MYOPIA(nearsightedness) or HYPEROPIA(far-
sightedness), or signal conditions of the eye such
as CATARACTor GLAUCOMA.
The ophthalmologist tests for basic VISUAL FIELD
by having the person focus on an object in the dis-
tance and signal when he or she can see an object
(such as a pen the ophthalmologist holds) that
moves into the field of normal vision. This test
assesses peripheral vision and helps detect sco-
tomas (small blind spots in the field of vision),
which are both symptoms of glaucoma and RETINI-
TIS PIGMENTOSA.Slit Lamp Examination
The SLIT LAMP EXAMINATION, also called a biomicro-
scopic examination, uses light focused as an elon-
gated slit in combination with magnification. Slit
lamp examination allows the ophthalmologist to
closely examine the front structures of the eye
including the sclera, CORNEA, iris, andLENS. It is a
common procedure for diagnosing cataract. The
ophthalmologist may also use FLUORESCEIN STAINING
to check for CORNEAL INJURYsuch as ABRASIONSor
lacerations.Ophthalmoscopy
The ophthalmoscope is a hand-held device that
resembles a flashlight. It has narrowly focused
beam of light and a magnifying lens. The ophthal-
mologist uses it to examine the inner structures of
the back of the eye known collectively as the fun-
dus: the retina, optic disk, and macula. The oph-
thalmologist usually dilates the pupil for
OPHTHALMOSCOPY. This test helps detect numerous
problems of the eye including RETINAL DETACHMENT,
RETINOPATHY, OPTIC NERVE ATROPHY, and PAPILLITIS.
Conditions such as glaucoma cause characteristic
changes to the fundus.Tonometry
The tonometer is a device that measuresINTRAOCU-
LAR PRESSURE(the pressure within the eye). The
most simple variation involves measuring the
force it takes for a puff of air to indent the cornea,
a noncontact test. For more accurate results the
ophthalmologist numbs the eye with anesthetic
drops and touches a TONOMETRYprobe against the
surface of the eye to measure the pressure.
Tonometry is a basic screening test for glaucoma,
for which increased intraocular pressure is a key
symptom.
See also AMSLER GRID; REFRACTION TEST; SCOTOMA;
VISION HEALTH.ophthalmoscopy Examination of the EYEusing
an ophthalmoscope, a hand-held, lighted magnify-
ing lens. The ophthalmoscope projects a narrowly104 The Eyes