Ophthalmoscopy is an essential
skill for all clinicians. Like other clinical skills, mastery is
conditional on proper technique and practice, practice, practice.
If you learn the proper techniques early in your education, you
can become a skilled examiner of the ocular fundus by the time you
earn your MD.
I. Instruments
II. Preparation
III. To Dilate or Not To Dilate
IV. Instrument Settings
V. Orientation and Landmarks
VI. What Am I Seeing?
VII.
Precautions and Comfort Considerations
VIII.
Practical Applications and Limitations
I.
Instruments
| The standard instrument
for clinical examination of the ocular fundus has been the
“direct” ophthalmoscope for many years. In this
country, the most common model has been the standard head
made by Welch-Allyn. This is a monocular viewer with various
settings that allow focusing and adjustment of the light source
to accommodate the viewer and to evaluate various features
of the fundus. |
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| Recently, Welch Allyn introduced
the Panoptic ophthalmoscope, a radically different instrument
that provides a much larger view of the fundus, and facilitates
viewing even through an undilated pupil. It is also a monocular
instrument that provides “direct” visualization
of the fundus with a variety of settings and attachments for
ocular examinations. |
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II.
Preparation
Paying attention to several details before
you begin can greatly enhance the success of your viewing efforts.
If possible, dim the room lights to avoid light distractions and
maintain your attention to details. The patient should be seated
comfortably (or lying supine in bed) to minimize head movement.
Ask the patient to fixate on a target directly ahead or above the
face at a distant target. It is helpful to warn patients that your
head may block their fixation but not to move their eyes or head
if you do.
The observer also should be stabilized in
order to maintain the correct viewing angle and distance from the
eye. You may wish to place your free hand on the patient’s
shoulder or brow, but it is preferable to use the edge of the bed
or the back of the chair.
III.
To Dilate or Not To Dilate
It is obvious that the best view of the fundus
is obtained through a dilated pupil. This is especially true of
older patients. Miosis occurs as part of the normal aging process,
and additional difficulties often result from deterioration of the
media due to cataracts, etc.
Note, however, that even with dilation, only
approximately one-third of the fundus is visible with a direct ophthalmoscope.
Fortunately, the area most visible is the posterior pole where the
ocular findings of many systemic diseases, such as hypertension
and diabetes are located. This includes the disk and the macula,
but if peripheral disease such as retinal tears or detachments is
suspected, other techniques like indirect ophthalmoscopy must be
used.
IV.
Instrument Settings
The ophthalmoscope should be prepared for
the specific viewer and patient. Using the standard head, set the
diopter power to “0”, and follow the directions for
the Panoptic to make it compatible with your refraction, if any.
Both patient and observer should remove their glasses, but contact
lenses do not need to be removed.
Adjust the size of the incident light beam
to approximate the size of the patient’s pupils. If the size
of the light source is much larger than the pupil, reflected rays
may cause glare and dazzle that interferes with detailed examination.
Turn on the light to approximately one-half
the maximum intensity to begin, and then adjust for optimum viewing
when the fundus is in view. Do not use maximum intensity especially
when using instruments with halogen bulbs as the brightness can
be uncomfortable for patients, especially when viewing the macula.
V.
Orientation and Landmarks
| The
optic disk is in the same location in everyone, and is easy
to identify. Therefore, if you can find the disk right away,
it is usually easier to maintain your orientation and to adjust
your viewing angle to see other structures. Use your right
eye to view the patient’s right eye, and your left for
the patient’s left. (With the PanOptic, it is possible
to use the same eye to view both patient eyes if necessary
but it is not recommended).
The
observer directs the light from the ophthalmoscope at the
pupil at an angle of 15-20 degrees temporally from the patient’s
line of sight (visual axis), at a distance of approximately
10-12 inches from the patient’s eye. Aiming your ophthalmoscope
at the pupil along the axis of the white line in the above
illustration, you should be able to see a red reflex in the
pupil (if you cannot find a red reflex, it may mean that a
cataract or other obstruction precludes fundus examination).
Keeping the red reflex in your view, move closer until the
field of view fills your viewer (about 1” from the eye
with the standard ophthalmoscope). Maintain this position
as you slightly change the angle of the ophthalmoscope head
to examine other areas of the posterior pole. |
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This
is the right eye illustrating the relationship of the macula
to the optic nerve. Note that to find the disk, the observer
must aim 15-20 degrees temporally from the patient’s line
of sight. For the left eye the observer moves to the patient’s
left side. |
If you do
not see the outline of the disk with this technique, stop, move
back 10 inches, and try again, perhaps using a slightly different
angle. While in the proper position, you may do a brief search for
the disk, but prolonged searching by following vessels, for example,
is usually unproductive. More importantly, patients become fatigued
rather quickly from the bright light and effort required for cooperation.
The most
important skill to learn while practicing is to find the viewing
angle necessary to locate the optic disk with a minimum of effort.
This ensures that that you will have a cooperative, relaxed patient
while you are visualizing the fundus, and your examination will
be spent on a productive evaluation.
VI.
What Am I Seeing?
To ensure
that a thorough examination of all pertinent areas is performed,
it is useful to develop a technique of examination that includes
all areas to be examined and the specific findings to note.
Beginning
with the optic nerve head, since that should be the first target
seen, adjust the focus on your ophthalmoscope to sharpen the view
as much as possible. Note the color and size of the disk, the size
of the cup relative to the total disk size, the presence of hemorrhages,
the location and caliber of the central retinal vessels, the sharpness
of the disk margins, and whether there is any edema or elevation.
Move the
light temporally one and one-half disk diameters and you should
be in the central macula. Note the presence or absence of hemorrhages
and exudates, pigmentary clumping or absence, and any scars that
may be present. Move back to the optic disk, and from there follow
each of the main arterial and venous branches into each of the four
quadrants as far as you can, again noting the caliber and color
of the vessels, the appearance of any pigmentary changes, and search
for hemorrhages and exudates in each area.
It is also
helpful to note for future reference the clarity of your view and
any observation difficulties.
VII.
Precautions and Comfort Considerations
A good examination
of both fundi is an intensive task for both patient and observer.
In particular, the need to minimize movement while a bright light
is shining into your eye can cause considerable discomfort and it
is considerate to allow the patient to occasionally rest for 10-15
seconds or so during a prolonged examination. The need for close
face-to-face positioning is also discomfiting for some people. Usually
about 10 seconds of observation is about the maximum tolerated before
a 10 second break is necessary. Using frequent breaks during difficult
examination allows a more detailed and thorough examination than
attempting to do everything with one viewing.
VIII.
Practical Applications and Limitations
Examination
of the ocular fundus is an important component of the clinical evaluation
in many diseases. It is essential in patients with diabetes
mellitus, increased intracranial pressure, and glaucoma, for example.
However, it is important to understand its limitations as well.
Firstly, no stereopsis is possible since one can only obtain a monocular
view. Secondly, only the posterior, central fundus can be
visualized, and the majority of the peripheral fundus cannot be
seen. Therefore, if a retinal tear or detachment is suspected, or
if there is a significant risk of retinoblastoma, or histoplasmosis,
other techniques must be used.
Direct ophthalmoscopy
is therefore a useful clinical tool which should be part of every
clinician’s examination routine. If utilized with skill, the
practitioner can apply an important diagnostic procedure to many
of the diseases encountered in everyday practice. Knowing its limitations
can lead to appropriate referrals and more detailed evaluations.
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