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7/25/2019 B20M01 8-part Eye Examination.pdf
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8-Part Eye Examination BLOCK 20MODULE 0
Ophthalmologists
Page 1of 11
SUMMARY/OUTLINE
I. Distance Acuity Test
II.
External Exam
III.
Pupillary Exam
IV.
Motility Exam
V.
Visual Fields (Confrontation Test)
VI. Tonometry
VII.
Ophthalmoscopy
VIII.
Slit-lamp Biomicroscopy
DISTANCE VISUAL ACUITY
1.
Ask the patient to stand or sit at a designated testing
distance (20 feet)
2. Occlude the left eye (testing one eye at a time)
3. Ask the patient to identify each letter in the chart, on
the lines of successively smaller optotypes, until patient
correctly identifies only half the optotypes on a line
4. Note the corresponding acuity measurement shown at
the line of the chart
5.
Repeat above steps for the left eye, with the right eye
covered
6. Retest acuity with the patients with low vision, e.g.
counting fingers, hand motion, light perception, etc.
Visual acuity can be tested either for distance or near,
conventionally at 20 feet (6 meters) and 14 inches (33 cms)
away, respectively, but distance acuity is the general standard
for comparison. For diagnostic purposes visual acuity is
always tested separately for each eye, whereas binocularvisual acuity is useful for assessing functional vision, such as
for assessing the eligibility to drive.Vaugn Asburys General Ophthalmology 39
thEdition
SNELLENS CHART
Distance visual acuity test should be the first thing to do
during the 8 part eye exam. You should do this before
palpating, or putting any eye medication or drugs so that
visual acuity is not altered because of the prior tests
administered.
In using the snellens chart, place the patient 20 feet away
from the chart.
Remember to test each eye separately and be tested with
and without corrective lenses
But in some clinics, there is only limited space, so they
minimize the distance by converting them to smallerdistances.
The largest letter E is equivalent to 20/200. If the patien
cannot read the letter E, move the patient 5 feet closer
until the patient reaches 5 feet away. Note the distance
where the patient is able to read the letter E. If the patient
still cannot read at 5 feet, proceed to counting finger test.
Some clinics may use meters. Patients usually placed 6
meters away from the chart.
Visual acuity is scored as a fraction (eg, 20/40). The first
number represents the testing distance between the chart
and the patient, and the second number represents thesmallest row of letters that the patients eye can read. Hence
normal vision is 20/20 and 20/60 acuity indicates that the
patients eye can only read from 20 feet letters large enough
for a normal eye to read from 60 feet.Vaugn Asburys General Ophthalmology 39
thEdition
For pediatric patients, you can use figures or the tumbling
E charts
Other patients can use the Jaeger chart. the patient is
scored depending on which line of sentences he can read
J10 is the biggest and J1 is the normal acuity.
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Example result
With
correction
Without
correction
FAR SIGHT
OS 20/150 20/20
OD 20/300 20/20
NEAR SIGHT
OS J8 J1
OD J10 J1
COUNTING FINGERS
By convention, ophthalmologists test first the right eye. If
it is known that the other eye is buron maybe the patient
complained of it before assessment, check the buron eye
first.
In counting fingers, place your finger 1 ft away from the
patient and let the patient count the fingers you are
showing to him. If the patient cannot count at 1 feet away,
move 1 more feet away until you reach the maximum of 3
feet. Record the distance where the patient can count the
fingers shown to him.
After the maximum of 3 feet and the patient cannot count
the fingers, proceed to light perception test.
HAND MOTION TEST
Make sure that you move your hands against the light.
LIGHT PERCEPTION TEST
Make sure to turn off the lights
The patient unable to read the largest (20/200) letter on a
Snellen chart should be moved closer to the chart until that
letter can be read. The distance from the chart is then
recorded as the first number. Visual acuity of 5/200 means
that the patient can identify correctly the largest letter from a
distance of 5 feet but not further away. An eye unable to read
any letters is tested by the ability to count fingers. CF at 2 ft
indicates that the eye was able to count fingers held 2 feet
away but not farther away. If counting fingers is not possible,
the eye may be able to detect a hand moving vertically or
horizontally (HM, or hand motions vision). The next lower
level of vision would be the ability to perceive light (LP, or
light perception). An eye that is totally blindis recorded as
having no light perception (NLP).Vaugn Asburys General Ophthalmology 39
thEdition
EXTERNAL EXAMINATION
1.
Observe the facial skin for any dermal or vascular
changes; note any lesions or evidence of trauma
2. Note any significant asymmetry of facial bones
3. Note the lid position; assess effectiveness of eyelid
closure and strength of the orbicularis muscles if
appropriate
4. Palpate the bony orbit for any lesion or deformity
This is performed before studying the eye under
magnification
Gross inspection and palpation: lesions, growth,
inflammatory signs (swelling, erythema, warmth,
tenderness)
Check for the ff:
o position of eyelids (ptosis, lid retraction)
o asymmetry can be quantified by measuring the
central width (in mm) of palpebral fissure (space bet
lower and upper lid margins)
o abnormal motor fxn of the lids (upper lid elevation,
forceful lid closure) may be due to neurologic o
primary muscular abnormalities
o malposition of the globe (proptosis) that may occur
in orbital disease
o bony orbital rim and periocular soft tissue
General facial evaluation:
o enlarged preauricular LN, sinus tenderness, tempora
artery prominence, skin/mucous membrane
abnormalities
o You canauscultate for bruit at the temporal side of
the orbit or directly at the globe. This can help youdetect carotid sinus fistula
PUPILLARY EXAMINATION
1. Turn off the light to decrease the room illumination
2. Ask the patient to maintain fixation on a distance target
3.
Shine a bright handheld light directly into the right eye
by approaching it from the side or from below
4. Record the direct pupillary response to light in the right
eye in terms of briskness of the response; observe the
consensual reflex by noting the response to light of the
non-illuminated pupil5. Repeat above steps for the left eye
6. Enumerate the steps in performing the swinging flash
light test and explain the clinical significance of relative
afferent papillary defect (Marcus Gunn pupil)
Assessment of pupil function should be done before any
drops are instilled in the eye and before the cornea is
touched (eg, applanation tension or Schirmer test).
Examination of the pupils with a light stimulus provides
evidence of the health of both the afferent and efferent
systems. In addition to light, the pupils also respond to
accommodation and convergence for clear and single vision
at near. The pupils will constrict equally when either
accommodation or convergence is stimulated by a nea
object. When all 3 actionsaccommodation, convergence
and miosisoccur simultaneously, this is called the synkinetic
near response.
Pupil function is evaluated with a bright penlight or other
intense, small light in a dimly illuminated room. Pupil or iris
abnormalities found with the naked eye can then be more
thoroughly evaluated using the biomicroscope. The pupils are
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evaluated for size, shape, direct light response, consensual
response, and near response.
SIZE
In dim illumination, the average pupil diameter is 3 or 4 mm.
This is ascertained by shining the light from below the
patients nose so that the pupils are just visible to the
examiner; the light is not shone directly into the patients
eye. Pupils smaller than 2 mm are said to be miotic; pupilslarger than 6 mm are mydriatic. Miotic pupils may be caused
by antiglaucoma medications, chronic iris inflammation, age,
or a neurologic disorder. Abnormal mydriasis is caused by
certain drugs, neurologic disorders, iris injury, or acute
glaucoma. The pupils should be equal in size, although a
small difference (1 mm) may be a normal variation. I f they are
unequal (anisocoria), the difference between them should be
further evaluated in both dark and bright room illumination.
SHAPE
Both pupils should be round. The pupils are normally
centered or a little nasal in the iris. An eccentric pupil may be
the result of faulty embryonic development, injury,
intraocular surgery, or inflammation. In addition to beingeccentric, a pupil may also have an unusual shape.
DIRECT LIGHT RESPONSE
In dim room illumination, the patient is instructed to look at a
distant target (this prevents the pupillary response to a near
stimulus). The light source is presented to each eye
separately and slightly off center to avoid the near response.
Each pupil should exhibit a brisk response and constrict to
about 2 mm.
CONSENSUAL RESPONSE
The consensual response is the simultaneous and equal
response of one pupil when the other pupil is being
stimulated by direct illumination or a near target. If the
stimulated pupil constricts normally, then the consensual
response of the other pupil will produce equal constriction
without direct light stimulus.
The pupils should be symmetric, and each one should be
examined for size, shape (circular or irregular), and reactivity
to both light and accommodation. Pupillary abnormalities
may be due to (1) neurologic disease, (2) intraocular
inflammation causing either spasm of the pupillary sphincter
or adhesions of the iris to the lens (posterior synechiae), (3)
markedly elevated intraocular pressure causing atony of thepupillary sphincter, (4) prior surgical alteration, (5) the effect
of systemic or eye medications, and (6) benign variations of
normal.
SWINGING PENLIGHT TEST FOR MARCUS GUNN PUPIL
As a light is swung back and forth in front of the two pupils,
one can compare the reactions to stimulation of each eye,
which should be equal. If the neural response to stimulation
of the left eye is impaired, the pupil response in both eyes
will be reduced on stimulation of the left eye compared to
stimulation of the right eye. As the light is swung from the
right to the left eye, both pupils will begin to dilate normally
as the light is moved away from the right eye and then not
constrict or paradoxically widen as the light is shone into the
left eye (since the direct response in the left eye and
the consensual response in the right eye are reduced
compared to the consensual response in the left eye and
direct response in the right eye from stimulation of the righ
eye). When the light is swung back to the right eye, both
pupils will begin to dilate as the light is moved away from the
left eye and then constrict normally as the light is shone into
the right eye. This phenomenon is called a relative afferen
pupillary defect (RAPD).Vaugn Asburys General Ophthalmology 39
thEdition
MOTILITY EXAMINATION
1. Sit facing the patient. Hold finger on or small fixation
target at eye level about 10-14 inches in front of the
patient, with the patient looking straight ahead.
2. Ask the patient to follow the target as you move it into
the six cardinal fields and up and down along the midlineElevate the upper eyelid with a finger on your free to
observe downgaze
3. Note whether the amplitude of eye movement is norma
or abnormal in both eyes
4.
Note any nystagmus that may be present
5. Determine alignment using the Hirschberg method of
corneal light reflection test hold a penlight in front o
the patient eyes at a distance of approximately 2 feet
directing the light at the midpoint between the two eyes
of the patient; instruct the patient to look directly at the
light; compare the position of the two corneal light
reflections and record the estimated result
The extraocular muscles include: the medial, inferior, and
superior recti, the inferior oblique, and levator palpebrae
muscles, all innervated by the oculomotor nerve (III); the
superior oblique muscle, innervated by the trochlear nerve
(IV); and the lateral rectus muscle, innervated by the
abducens nerve (VI).
The precise action of any muscle depends on the orientation
of the eye in the orbit and the influence of the orbita
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connective tissues, which regulates the direction of action
of the extraocular muscles by acting as their functional
mechanical origins (the active pulley hypothesis).
Mnemonic: "SO-4, LR-6, All the rest 3" (ie Superior Oblique by
CN 4, Lateral rectus by CN 6, and all the other EOMs by CN 3).
TESTING OF THE VISUAL FIELD
The patient is asked to follow a target with both eyes as it is
moved in each of the four cardinal directions of gaze. The
examiner notes the speed, smoothness, range, and symmetry
of movements and observes for unsteadiness of fixation (eg,nystagmus). Impairment of eye movements can be due to
neurologic problems (eg, cranial nerve palsy), primary
extraocular muscular weakness (eg, myasthenia gravis), or
mechanical constraints within the orbit limiting rotation of
the globe (eg, orbital floor fracture with entrapment of the
inferior rectus muscle). Deviation of ocular alignment that is
the same amount in all directions of gaze is called comitant.
It is incomitant if the amount of deviation varies with the
direction of gaze.Vaugn Asburys General Ophthalmology 39
thEdition
SIMPLE TEST OF BINOCULAR ALIGNMENT/ HIRSCHBERG
METHOD
Procedure:
1. Have the patient look toward a penlight held several feet
away. (33 cms according to Vaughan & Asburys 18th ed.
Page 244)
2. Note for the pinpoint light reflection, or reflex,.
Note: In normal eyes, pinpoint light reflection, or reflex,
should appear on each cornea and should be centered over
each pupil if the two eyes are straight in their alignment.
If the eye positions are convergent, such that one eye points
inward (esotropia), the light reflex will appear temporal to
the pupil in that eye. If the eyes are divergent, such that one
eye points outward (exotropia), the light reflex will be
located more nasally in that eye.Vaugn Asburys General Ophthalmology 39
thEdition
Landmarks to remember:
0mm Light reflection is at the center of the pupil
1mm Light reflection is in between the center of the pupil
and the pupillary border
2mm Light reflection is at the pupillary border
3mm Light reflection is in between pupillary border and
limbus
4mm Light reflection is at the limbus
KIMPSKY TEST
The Krimsky test is essentially the Hirschberg test, but with
prisms employed to quantitate deviation of ocular
misalignment by determining how much prism is required to
centre the reflex [2] The Krimsky test is advisably used fo
patients with tropias, but not with phorias.https://en.wikipedia.org/wiki/Hirschberg_test
COVER TEST
- More accurate method of verifying normal ocular
alignment.The test requires good vision in both eyes.
Procedure:
1. Ask the patient to gaze at a distant target with both
eyes open. If both eyes are fixating together on the
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target, covering one eye should not affect the
position or continued fixation of the other eye.
2. Suddenly covers one eye and carefully watches to see
that the second eye does not move (indicating that it
was fixating on the same target already). If the
second eye was not identically aligned but was
instead turned abnormally inward or outward, it
could not have been simultaneously fixating on the
target. Thus, it will have to quickly move to find the
target once the previously fixating eye is covered.
Fixation of each eye is tested in turn.
Note!
An abnormal cover test is expected in patients with diplopia.
However, diplopia is not always present in many patients with
long-standing ocular misalignment. When the test is
abnormal, prism lenses of different power can be used to
neutralize the refixation movement of the misaligned eye
(prism cover test). In this way, the amount of eye deviation
can be quantified based on the amount of
prism power needed.
BRUCKNER TEST
The Brckner test is a qualitative assessment of ocula
alignment. This test is done under dark room illumination
and the direct ophthalmoscope aperture set on the largest
aperture setting so as to equally illuminate both eyes. The
examiner is viewing at about 1 meter away and observing the
relative brightness of the fundus reflex from each eye. A
whiter and brighter reflex is noted in the eye that is
strabismic. To confirm a difference in color, retestmonocularly to note any changes to the reflex. The
strabismic eye will appear whiter and brighter as a result of
the fundus reflection emanating from outside of the
pigmented macula region.http://apps.ketchum.edu/ceonline/courseview.a...
VISUAL FIELDS EXAMINATION (CONFRONTATION TEST)
1. Seat the patient and make sure the eye not being testes
is occluded
2. Seat facing the patient at a distance of about 1m. close
your eye that is directly opposite the patients occluded
eye
3.
Ask the patient to fixate on your nose or on your open
eye
4. Hold your hands stationary midway between yoursel
and the patient is opposite quadrants about 30 degrees
from central fixation
5. Quickly extend then retract a finger or fingers on one
hand in one quadrant of the monocular field asking the
patient to state the number of fingers seen
6.
Repeat all four quadrants, testing at least twice per
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quadrant
7. Diagram the confrontation field if an abnormality is
detected
Make sure to test each eye separately. When occluding
the other eye, dont depress the eyeball because it may
cause blurring of vision.
During the 8part eye exam, we are expected to use only
the manual test. Automated perimetry is done in sophisticated diagnostic
centers. Is uses a machine that accurately records the
visual fields. The machine can also determine how much
light the patient can see by altering the intensity of the
light being shown to the visual fields.
It is advisable to make a diagram as to which visual field
is blinded because it can guide you in diagnosis
If the patient has bitemporal hemianopia (number 2)
what possible disease can lead to such problem knowing
that the optic chiasm is the structure affected? Pituitary
tumors.
In automated perimetry:
TONOMETRY
1. Enumerate and differentiate the methods of measuring
intraocular pressure
globe can be thought of as an enclosed compartment
through which there is a constant circulation of aqueous
humor
this fluid maintains the shape and a relatively uniform
pressure within the globe tonometry is the method of measuring intraocular
pressure using calibrated instruments.
normal range is 10 to 21 mm Hg
less corneal indentation is produced as intraocular
pressure rises.
since both methods employ devices that touch the
patients cornea, they require topical anesthetic and
disinfection of the instrument tip prior to use.
with any method of tonometry, care must be taken to
avoid pressing on the globe and artificially increasing its
pressure.
APPLANATION TONOMETRY
- intraocular pressure is determined by the force required to
flatten the cornea by a standard amount. The force required
increases with intraocular pressures.
- the GOLDMANN APPLANATION TONOMETERis attached to
the slitlamp and measures the amount of force required to
flatten the corneal apex by a standard amount.
- the higher the intraocular pressure, the greater the force
required.
- Goldmann applanation tonometer is a more accurate
method than Schiotz tonometry
- following topical anesthesia and instillation of fluorescein
the patient is positioned at the slitlamp and the tonometer isswung into place. To visualize the fluorescein, the cobalt blue
filter is used with the brightest illumination setting. After
grossly aligning the tonometer in front of the cornea, the
examiner looks through the slitlamp ocular just as the tip
contacts the cornea. A manually controlled counterbalanced
spring varies the force applied by the tonometer tip.Upon
contact, the tonometer tip flattens the central cornea and
produces a thin circular outline of fluorescein. A prism in the
tip visually splits this circle into two semicircles that appear
green while viewed through the slitlamp oculars. The
tonometer force is adjusted manually until the two
semicircles just overlap, as shown in Figure 210. This visua
end point indicates that the cornea has been flattened by the
set standard amount. The amount of force required to do this
is translated by the scale into a pressure reading in
millimeters of mercury.
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- accuracy of intraocular pressure measurement is affected by
central corneal thickness. The thinner the cornea, the more
easily it is indented, but the calibration of tonometers
generally assumes a cornea of standard thickness. If the
cornea is relatively thin, the actual intraocular pressure is
higher than the measured value, and if the cornea is relatively
thick, the actual intraocular pressure is lower than the
measured value. Thus ultrasonic measurement of corneal
thickness (pachymetry) may be helpful in assessment of
intraocular pressure. The Pascal dynamic contour tonometer,
a contact but non-applanating technique, measures
intraocular pressure independent of corneal thickness.
- other applanation tonometers are the Perkins tonometer, a
portable mechanical device with a mechanism similar to the
Goldmann tonometer, the Tono-Pen, a portable electronic
applanation tonometer that is reasonably accurate but
requires daily recalibration, and the pneumatotonometer,
which is particularly useful when the cornea has an irregular
surface. The Perkins tonometer and Tono-Pen are commonlyused when examination at the slitlamp is not feasible, for
example, in emergency rooms in cases of orbital trauma with
retrobulbar hemorrhage and in operating rooms during
examinations under anesthesia.
SCHIOTZ TONOMETRY
- now rarely used, measures the amount of corneal
indentation produced by preset weights
- advantage of this method is that it is simple, requiring only a
relatively inexpensive, easily portable hand-held instrument.
It can be used in any clinic or emergency room setting, at the
hospital bedside, or in the operating room, but it requires
greater expertise and has generally been superseded by
applanation tonometers.
NONCONTACT TONOMETRY
- noncontact (air-puff) tonometer is not as accurate as
applanation tonometers.
- small puff of air is blown against the cornea.
- air rebounding from the corneal surface hits a pressure
sensing membrane in the instrument.
- does not require anesthetic drops, since no instrument
touches the eye. Thus, it can be more easily used by
optometrists or technicians and is useful in screening
programs.
OPHTHALMOSCOPY
1.
Position the patient about 2 feet away
2. Turn off the light to dim the room illumination
3. Set the focusing lens of the ophthalmoscope to zero
4.
Check the red reflex from a distance of 2 feet
5.
Approach the patients eye; the instrument is steadied
against the patients face by resting the ulnar border of
the hand holding the instrument against the patients
cheek; the thumb of the free hand raises the upper lid
6.
Instruct the patient to stare into the distance
7. Dial the ophthalmoscopes focusing lenses into place to
clarify the fundus image
8.
Find the optic disc by following a retinal blood vessel
9. Examine the peripapillary retina
10. From the optic disc, follow the blood vessels outward to
examine the four quadrants around the posterior pole
11. Check for foveal reflex
THE DIRECT OPHTHALMOSCOPE
This instrument consists of a single aperture through which
light is projected into the subjects eye and the examiner
views the eye. It provides a magnified image (15) and a field
of view of some 6.510 degrees. A set of corrective lenses can
be dialled into the aperture. These enables the focal point of
the instrument to be adjusted. The rack of lenses usually
contains equal numbers of positive and negative spheres
which can be dialled up to take account of the patient and/or
examiners refractive status. If examiners wish to wear their
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glasses, they can do so, and effectively they will need a zero
lens in the eyepiece. The patients refraction must also be
taken into account and the relevant lens dialed into place.
With highly myopic or hypermetropic patients, their glasses
can be left on and used to nullify the effect of the refractive
variation. Alternatively plus and minus 10 or 20 D lenses can
be positioned in the sight aperture to take account of very
high hypermetropia or myopia. The size and brightness of the
illumination spot can be varied with the appropriate controls.
Additional features vary among the different models but
include a slit filter, producing a vertical slit of light which can
be used to examine contours or elevations on the fundus, a
grid for assessing the size of a fundus lesion, and a green filter
for red-free viewing. This latter filter will make red features,
such as haemorrhages, stand out due to increasing contrast
between the various shades of red and orange which reflect
from the fundus. Some ophthalmoscopes also include a
cobalt blue filter for use with fluorescein dye.
The view obtained with this instrument has a narrow angle of
view and a high magnification. The more myopic the patient,
the more effective the magnifying effect. This is useful forexamining the optic nerve head; however the view is
monocular and two-dimensional.
METHOD OF USE
1. Inform patients that you are going to look at their eye
with a bright light and that you will have to get very close
to their face. Instruct them to breathe normally.
2.
The instrument is held to the examiners eye with the
illumination system switched on and for steadiness and
ease of use a hand can be placed on the patients
shoulder.
3.
The examiners right eye is used for the patients right
eye and the examiners left for the patients left eye. If
the examiner finds it difficult to close one eye, or the
other, then it can be left open with practice the brain
manages to ignore the image from the non-examining
eye.
4. The correct lens, as described above, is dialled into the
aperture.
5.
The patient is asked to fix on a distant object and is told
to maintain that fixation, regardless of whether the
examiner gets in the way. The examiner thus knows
roughly where the patients macula is situated and the
optic disc will be just nasal to this.
6.
The examiner then points the instruments illuminationbeam into the patients pupil and obtains a red reflex
from a distance of about half a metre and slowly moves
towards the patient. At this point media opacities such as
cataract can be seen as black features against the red
reflex. The rheostat is used to adjust the brightness of
the light for the patients comfort. I f required, the front
of the eye, cornea, iris and lens can be examined with a
+10 lens dialed into the instruments lens bank.
7. Following this part of the examination the lens dial is
progressively turned towards zero to focus further back
into the patients eye and eventually reach the retina. It
must be stressed that the head of the ophthalmoscope
must be held very close to the patients eye in order to
gain the maximum field of view.Clinical Skills for the Ophthalmic Examination: Basic Procedures, 2
ndEdition
*For parts of the opthalmoscope: see last page
Macula is usually at temporal side while optic disc is on
the temporal side.
INDIRECT OPHTHALMOSCOPY
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Binocular Indirect Ophthalmoscopy (BIO) is a technique that
provides thorough view of the retina and vitreous through a
dilated pupil in order to evaluate the health of the interior of
the eye and to identify structural abnormalities that may be
associated with reduced visual acuity thereby aiding the
diagnosis of amblyopiaoptometry.osu.edu
Comparison Between Direct and Indirect OphthalmoscopyDIRECT INDIRECT
Magnified image Not magnified
Can see only small area Lets you see bigger area
If with cataract, cannot see Ideal if with cataracts
One handheld apparatus Uses a head gear and a
handheld condensing lenses
SLIT-LAMP BIOMICROSCOPY
1. Identify the different parts of the slit-lamp biomicroscope
2. Enumerate the different uses of the slit-lamp
The slitlamp is a table-mounted binocular microscope with a
special adjustable illumination source attached. A linear slit
beam of incandescent light is projected onto the globe,
illuminating an optical cross section of the eye. The angle of
illumination can be varied along with the width, length, and
intensity of the light beam. The magnification can be adjusted
as well (normally 10 to 16 power). Since the slitlamp is a
binocular microscope, the view is stereoscopic, or three-
dimensional.
Slitlamp photograph of a normal right eye. The curved slit of
light to the right is reflected off of the cornea (C), while the
slit to the left is reflected off of the iris (I). As the latter slit
passes through the pupil, the anterior lens (L) is faintly
illuminated in cross section.
The patient is seated while being examined, and the head is
stabilized by an adjustable chin rest and forehead strap.Vaugn Asburys General Ophthalmology 39
thEdition
Parts of Slit lamp biomicroscopy
Viewing Arm.The binocular eyepieces provide stereoscopic vision and can
be adjusted to accommodate the examiner's interpupillary
distance. The focusing ring can be twisted to suit the
examiner's refractive error.
The magnification element can be adjusted with the side dial.
Illumination Arm
The illumination arm can be swung 180 degrees side to side
on its pivoting bases allowing the examiner to direct the light
beam anywhere between the nasal and temporal aspect o
the eye examination.The dimension of the light beam can be
varied in height and width with these levers. It can provide
diffuse or focal illumination as an optical cross-section of the
anterior segment.Cobalt blue, or green filters can be selected
with this lever.
The Patient Positioning Frame
The patient positioning frame consist of two upright meta
rods to which are attached a forehead strap and a chin rest.
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The chin rest height can be adjusted with the knob just below
it.
The JoystickThe joystick allows for focusing by shifting forward,
backward, laterally or diagonally. The joystick can also be
rotated to lower or elevate the light beam.
The locking screw located at the base secures the slit lamp
from movement when it is not in use.
Just below the slit lamp table on the left is the ON switch and
provides high or low options in light intensity.
Uses of Slit lamp
1. To visualize the anterior half of the globethe
anterior segment.
2.
To study the details of the lid margins and lashes,
the palpebral and bulbar conjunctival surfaces, the
tear film and cornea, the iris, and the aqueous can
be studied.
3.
Through a dilated pupil, the crystalline lens and theanterior vitreous can be examined as well.
4. Because the slit beam of light provides an optica
cross section of the eye, the precise anteroposterior
location of abnormalities can be determined within
each of the clear ocular structures (eg, cornea, lens
vitreous body).
5. The highest magnification setting is sufficient to
show the abnormal presence of cells within the
aqueous, such as red or white blood cells or pigment
granules. Aqueous turbidity, called flare, resulting
from increased protein concentration can be
detected in the presence of intraocular
inflammation. Normal aqueous is optically clear
without cells or flare.Vaugn Asburys General Ophthalmology 39
thEdition
Other uses of slit lamp biomicroscope:- Internet source.
1. Routine observation of ocular adnexia
2. Routine investigation of posterior segment
3. Monitoring signs and symptoms of anterior segment
conditions
4. Further "special eye" investigations
Definition of TermsConjugate movement: Movement of the eyes in the same
direction at the same time.
Deviation: Magnitude of ocular misalignment, usually
measured in prism diopters but sometimes measured in
degrees.
Comitant deviation: Deviation not significantly affected by
which eye is fixing or direction of
gaze, typically a feature of childhood (nonparetic) strabismus.
Incomitant deviation: Deviation varies according to which
eye is fixing and direction of gaze,
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usually a feature of recent onset extraocular muscle paresis
and other types of acquired
strabismus.
Primary deviation: Incomitant deviation measured with the
normal eye fixing).
Secondary deviation: Incomitant deviation measured with
the affected eye fixing.
Ductions: Monocular rotations with no consideration of the
position of the othereye.
Adduction: Inward rotation.
Abduction: Outward rotation.
Supraduction (elevation): Upward rotation.
Infraduction (depression): Downward rotation.
Fusion: Formation of one image from the two images seen
simultaneously by the two eyes.Fusion has two aspects.
Motor fusion: Adjustments made by the brain in innervation
of extraocular muscles in order to
bring both eyes into bifoveal and torsional
alignment.
Sensory fusion: Integration in the visual sensory
areas of the brain of images seen with the twoeyes into one picture.
Heterophoria (phoria): Latent deviation of the eyes held
straight by binocular fusion.
Esophoria: Tendency for one eye to turn inward.
Exophoria: Tendency for one eye to turn outward.
Hyperphoria: Tendency for one eye to deviate upward.
Hypophoria: Tendency for one eye to deviate downward.
(See Hypotropia.)
Heterotropia (tropia):
Strabismus: Manifest deviation of the eyes that cannot be
controlled by binocular vision.
Esotropia: Convergent manifest deviation (crossed eyes).
Exotropia: Divergent manifest deviation (wall eyes).
Hypertropia: Manifest deviation of one eye upward.
Hypotropia: Manifest deviation of one eye upward. By
convention, in the absence of specific
causation to account for the lower position of one eye,
vertical deviations are designated by the
higher eye (eg, right hypertropia, not left hypotropia, when
the right eye is higher).
Incyclotropia: Manifest rotation of the 12 oclock meridian of
one eye about its anteroposterior
axis toward the midline of the head.Excyclotropia: Manifest rotation of the 12 oclock meridian of
one eye about its anteroposterior
axis away from the midline of the head.
Orthophoria: The absence of any tendency of either eye to
deviate when fusion is suspended.
This state is rarely seen clinically. A small phoria is normal.
Prism diopter (PD): The unit of angular measurement used to
characterize ocular deviations. A
1 diopter prism deflects a ray of light toward the base of the
prism by 1 cm at 1 m. One degree of
arc equals approximately 1.7 PD.
Secondary deviation: The deviation measured with the
paretic eye fixing and the
normal eye deviating.
Torsion: Rotation of the eye about its anteroposterior axis
Intorsion (incycloduction): Rotation of the 12 oclock meridian
of the eye toward the midline of
the head.
Extorsion (excycloduction): Rotation of the 12 oclock
meridian of the eye away from the
midline of the head.
Vergences (disjunctive movements): Movement of the two
eyes in opposite directions.
Convergence: The eyes turn inward.
Divergence: The eyes turn outward.
Versions: Binocular rotations of the eyes in qualitatively the
same direction.