Transcript Ocular motility examination

 The afferent visual system is broadly
designed to achieve 2 fundamental
goals:
(1) to detect the presence of objects within
the environment.
(2) to provide a high level of spatial
resolution for those objects that
command our attention
• The entire retina outside of the fovea is
devoted essentially to the detection of
objects. Only the fovea, which occupies a
tiny fraction of the total retinal area,
provides the fine-quality images that allow
us to read or perform highly precise
visuomotor tasks.
• Any imprecision in maintaining alignment
of the fovea on the moving target
degrades the appearance of the image.
• The need to maintain high-quality vision
despite any “relative movement” is
addressed by multiple ocular motor
systems .
SYSTEMS THAT CONTROL EYE
MOVEMENT
Pursuit system
 OKN system
Saccadic system
vergence system
vestibular
These are each controlled by different
anatomic pathways.
pursuit system
• To track relatively slow moving targets (no
faster than 30° per sec).
• Can do it through vestibulo -ocular
reflexes (VOR), which produce eye
movements in a direction opposite to that
of head movements.
• The VOR, however, attenuate fairly
quickly (ie, within seconds) during a
persistent period of relative motion.
Smooth pursuit
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Slow conjugate eye movement
Voluntary or involuntary
To keep image of a moving object at fovea
Mediated by parieto-occipito-temporalmesencephalic pathway
• Ipsilateral control
optokinetic nystagmus (OKN)
system
• Provides The capability of following
objects over a sustained period of motion.
• (OKN) system uses smooth pursuit to
track a moving object but then introduces
a saccade in the opposite direction when
the maximal amplitude of the pursuit
movement is reached or when the speed
of the moving object exceeds the maximal
velocity of the pursuit system
OKN
• Slow conjugate eye movement
• Involuntary
• To keep retinal images fixed during
prolonged head / body rotation
• Unknown pathway
• Response to acceleration
• Fades with sustained constant speed of
rotation
saccadic system
• Relatively fast moving targets cannot be
tracked but can be followed by the use of
relatively fast, back-to-back eye
movements generated by the saccadic
system.
• saccades, are “ballistic” movements—
ones that cannot be altered once initiated
saccade
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Fast conjugate eye movement
Voluntary
To bring object images to the fovea
Mediated by fronto-mesencephalic /
superior colliculus pathways
• Contralateral control
• Persistent foveation is controlled by
microsaccadic refixation movements .
vestibular
• Depends on vestibular motion receptors in the
semicircular canals in each ear and the
labyrinthine-pontine pathway
• Stimulation of horizontal canal results in
horizontal nystagmus
• Stimulation of posterior canal results in vertical
nystagmus
• Stimulation of anterior canal results in rotational
nystagmus
• Contralateral control
vestibular
• Produce a slow conjugate eye movement
• Involuntary
• To keep retinal images fixed during brief
head / body rotation.
Fixation: the ability to maintain attention
on an object
Convergence/divergence: the ability for
the eyes to turn in and turn out so they are
aimed at the same place in space.
Saccades: the ability of the eyes to
uniformly track, stop at an indicated position,
resume movement and return to a preset
position.
Stereopsis: the ability of eyes and brain
to interpret the presented information as a
three dimensional image.
Rotations and versions: testing the eye
muscles tracking (following) a moving
object.
Accommodation test: tests the
focusing/de-focusing optical system in the
eye.
Cover Test: to determine if the eyes are
properly aligned for a given distance.
Binocular Single Vision
• the state of simultaneous vision, which is
achieved by the coordinated use of both
eyes, so that separate and slightly
dissimilar images arising in each eye are
appreciated as a single image by the
process of fusion.
Motor Fusion
• It is the ability to align the eyes in such a
manner that sensory fusion can be
maintained. The stimulus for these
fusional eye movements is retinal disparity
outside panum’s area .
Oculomotor paresis results in a
limitation of saccades in specific directions
relative to the head (rightward, leftward,
upward and downward).
One possible solution is to adapt the
head position relative to the display so
that the entire display remains accessible
with eye movements.
• Ocular nystagmus is a constant
oscillation of the eye which results in an
inability to maintain a stable fixation.
• One possible solution is to find the head
position which minimizes the amplitude of
the oscillation.
• Strabismus is another condition where
only one eye is fixating while the other eye
is deviating from that direction.
• Phoria is a condition where deviation
appears only after some delay, for
example as a result of fatigue.
Examination of the eyeball
Observe the following points
A) Position – normally the two eyeball are
symmetrically placed in the orbit in such a way
that a line joining the center point of superior
and inferior orbital margins just touches the
cornea
Dr Sanjay Shrivastava
8 April 2016
21
Examination of the eyeball
b) Visual axis of eyeball
• Normally the visual axis of the eyeball is
simultaneously directed at same object
which is maintained in all the directions of
gaze.
• Deviation is the visual axis of one eye is
called squint.
Dr Sanjay Shrivastava
8 April 2016
22
Convergent Squint
Examination of the eyeball
c) Movement of eye ball
• The movement are tested uniocular
(duction) as well as binocularly (versions)
in all the 9 diagnostic positions of gaze.
• Uniocular – Adduction, abduction,
depression, elevation, depression and
elevation in adduction and abduction
•
Assessment of visual motor
system
Visual acuity
Inspection
Evaluation of ocular alignment
Version test
Others to aid Dx of supranuclear disorders
Convergence test
Saccades’ and pursuits’ movements
Doll’s eye movement
OKN test
Caloric responses
Ocular motility examination
Look at ( inspection)
 head posture:
1) Face turn- towards side of weakness
e.g. 6th CN palsy ,Duane’s
2) Head tilt- e.g. away from side of 6th
CN palsy.
3) Chin up/down
e.g. bilateral 6th CN palsy
(Inspection)
Ptosis - 3rd CN palsy
Primary position – manifest strabismus
Corneal reflexes – asymmetry indicates
deviation.
Pupils -anisocoria
Evaluation of ocular alignment
Corneal reflection tests
-Hirshberg’s test
-krimsk’s test
-Bruckner’s test
Cover tests
-Cover/uncover
-Alternate cover
- prism cover test
HIRSHPERG’S TEST
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Detect gross heterotopias
Based on purkinje sanson image no.1
Look at symmetry of light reflex
Normal reflex….just nasal to center of
pupil
 Abnormal reflex….each 1 mm of deviation
=7 degrees = 30 PD
COVER TESTS
• Based on fixation ability
• Normal fixation behavior….CSM
Cover/uncover …detect manifest deviation
Alternate cover ….detect total deviation (
manifest + latent)– dissociation test
• To measure angle of deviation….prism
cover test
• Check versions ( both eyes) and ductions
(one eye) in all 9 positions of gaze
-ask patient to follow target ( pen-torch)
-perform cover test in each position
-ask patient to report any diplopia during
test
look for any abnormality; under/overaction,
paresis/restriction .
Examination of EOM
3
4
1
6
Right side
7
Binocular Ocular Movements
3
5
4
5
2
1
2
8
6 7 8
Left side
1 = Dextroversion; 2 = Levoversion; 3 = Elevation;
4 = Dextroelevation ; 5= Levoelevation; 6= Dextrodepression;
7= Depression; 8 = Levodepression
• If there is any diplopia
……… indicates deviation
Uncrossed diplopia = eso –deviation
Crossed diplopia = exo – deviation
Hypertropic eye will see the lower image
• Ocular misalignments may be comitant or
incomitant.
• Incomitant misalignments indicate an
innervational problem or a mechanical
restriction.
• Ductions (ie, movement of a single eye with the
other eye covered) may be better than versions
in patients with innervational problems, with no
difference between ductions and versions noted
in patients with mechanical restrictions.
• Forced ductions are restricted with mechanical
disease and normal with paralytic disease,
unless the paralysis has caused chronic
contracture of the muscle.
• In patients with CN III palsy, the presence
or absence of afferent pupillary
involvement must be documented. Pupilinvolving lesions may indicate an
underlying posterior communicating artery
aneurysm, and neuroimaging studies are
required.
• If a vertical deviation is noted, head tilts
are performed…( parks-bielschewsky 3step test)
To identify a single underacting muscle in
vertical / torsional deviation.
Particularly useful in SO palsy
3 steps
Identify hypertropic eye
Identify gaze where disparity is greatest
Identify head tilt side where disparity is
greatest
Examine horizontal/vertical saccades
 ask patient to look rapidly between widely
separated targets
result: ---normal / slow
hypo/ hypermetric
 Useful in detecting internuclear
ophthalmoplegia
Smooth pursuit is tested by having the
patient slowly follow a moving target 1m a
way.
• Separating saccades from smooth pursuit may
be clinically important. Smooth pursuit may be
irregular in brainstem- cerebellar disease, and
catch-up saccades may be required.
• In Parinaud syndrome, upgaze saccades may
be affected more than upward smooth pursuit
early on in the disease.
• In patients with small pontine strokes involving
purely the paramedian pontine reticular
formation (PPRF), saccades may be affected
and smooth pursuit relatively preserved. This is
because the fibers of the latter eye movement
system do not synapse in the PPRF.
Examine convergence
assess to both accommodative and nonaccommodative target
normal / reduced
…….Hold a target in front of patient and
progressively bring it nearer , whilst
observing for convergence of the two eyes
Examine Doll’s eye movement
Normal / absent
 When a horizontal gaze palsy is suspected
 Hold the head of the patient and rotate it
from side to side
…………if the eyes deviate fully it
indicates intact pontine reflexes
……… supranuclear lesion
Examine OKN -horizontal / vertical
 slowly rotate an OKN drum in horizontal
and vertical direction
result : Normal / absent /convergence
retraction( vertical gaze palsy)
 Useful in cases of parinaud’s syndrome
Caloric response
• Caloric testing is dependent on endolymph
convection currents.
• Normal response
Warm water in the right ear produces a
right-beating nystagmus
coldwater in the right ear produces a leftbeating nystagmus