BLOCK 1: Clinical Exams
•Theme 1: Anamnesis
•Theme 2: Material
•Theme 3: Visual acuity
•Theme 4: Retinoscopy
•Theme 5: Subjective
•Theme 6: Cover Test
•Theme 7: Accomodation
Theme 6: Cover test
Utility
What is a strabismus?
What is a phoria?
6
7
15
Material
18
Method
19
Theme 6: Cover test
Method
19
Unilateral Cover
20
Description
21
Characterization of strabismus
28
Direction
30
Frequency
36
Magnitude
38
Laterality
45
comitance
49
Theme 6: Cover test
Cover – Uncover
53
Description
54
Characterization of strabismus
58
Direction
59
Magnitude
59
comitance
59
Cover – Alternating
64
Theme 6: Cover test
Self-evaluation
69
Bibliography
79
Utility
The cover test is an optometric test that can prove or
disprove the presence of a strabismus or a phoria.
The presence or absence of the fusional ability is
determined.
Utility
What is a strabismus
We are facing a strabismus when both eyes do
fle
fre
not simultaneously direct their visual axes on
object of interest….
What happens when an ocular deviation is
axis
produced?
Utility
What is a strabismus
When binocular vision exists, the
object of interest stimulates both foveas
simultaneously, thereby achieving a
fusion of the image on a cortical
level.
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In this case, what is called a Normal
Sensory Correspondence (NSC) exists.
fre
Utility
What is a strabismus
Facing an ocular deviation, the following effects could
be produced:
•
diplopia
•
confusion
fle + fre =
+
= Confusion
fle
fle + O =
+
= Diplopia
0
fre
Utility
What is a strabismus?
Facing these possibilities and uncomfortable effects,
the visual system can respond by trying to avoid
them through:
•
Abnormal retinal correspondence
•
Suppresion
•
Eccentric fixation
•
Torticollis
fle
0
fre
Utility
What is a strabismus?
Abnormal retinal correspondence
The fovea of the deviated eye
will not correspond with fixating eye,
thereby resulting in the binocular
function, point “0”.
0 fre
fle
ARC
Utility
What is a strabismus?
Suppression
The image that prevails is that which
only pertains to the directing eye.
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0 fod
Utility
What is a strabismus?
Eccentric fixation
It happens when the deviated eye,
in a monocular way, prefers to look at the
Occluder
object of interest with a distinct point of the
fovea
fle
0 fre
Utility
What is a strabismus?
Torticollis
There are different types of strabismus in
Habitual position
which diplopia and confusion only appear in certain
“sight” positions
This can make the patient present an
inclination of the head in order to maintain,
“in a habitual way”, sight in the position of
greatest comfort.
Ocular deviation
Paralysis of the
OS from the RE
Utility
What is a phoria?
A phoria is a latent deviation.
This deviation becomes apparent after the elimination of the fusion stimulus
(occluder, Maddox rod, prisms...)
The visual axes of both eyes are directed
at the object of interest thanks to the
utilization of fusional convergence
A phoria at a given distance implies that, at that distance and in that instant,
binocular vision exists
Utility
What is a phoria?
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fle
The type of fusional convergence to utilize
depends on the type of phoria
An endophoria utilizes the negative fusional
NFC
vergence (NFV) in order to bring both
visual axes onto the object of interest.
c
Utility
What is a phoria?
fre
fle
An exophoria utilizes the positive fusional
vergence (PFV) in order to bring the visual
CFP
axes onto the object of interest.
c
Material
• Optotype from distance
• Accomodative card
• Occluder
• Prisms
Method
By covering one of the two eyes and analyzing what is observed
Objective
Unilateral Cover
Detection of strabismus
Cover - Uncover
Detection of phorias
Alternating Cover Test
Evaluation of the totality of the
deviation
Method
By covering one of the two eyes and analyzing what is observed
Objective
Unilateral Cover
Detection of strabismus
Cover - Uncover
Detection of phorias
Alternating Cover Test
Evaluation of the totality of the
deviation
Method
Unilateral Cover
Detection of strabismus
Cover and uncover an eye, observing if in the other eye some
movement of fixation is produced
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fle
Movement?
e
Method
Unilateral Cover
If upon covering the right eye…
1. There is No movement of the left eye
fre
fle
fre
fle
Hide the left eye
e
e
The absence of movement tells of orthotropia (absence of strabismus)
Method
Unilateral Cover
Detection of strabismus
Observe whether movement of the uncovered eye
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fle
1. There is no movement
• Possible Orthotropia
(there is no strabismus)
Movement?
2. There is movement
e
• Tropia
(there is strabismus)
Method
Unilateral Cover
If upon hiding the right eye…
1. There is No movement of the left eye
fre
Hide the left eye
fle
fre
fle
The absence of movement
tell of orthotropia
(absence of strabismus)
e
e
Method
Unilateral Cover
If upon covering the right eye…
2. There is movement of the left eye
fre
fre
fle
fle
Indicates that the left eye was
deviated
e
The presence of movements tells of strabismus
e
Method
Unilateral Cover
If upon hiding the right eye…
2. There is movement of the left eye
fre
fle
e
fre
It indicates that the left eye was deviated
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e
Endotropia LE
Method
Unilateral Cover
If upon covering the right eye …
2. There is movement of the left eye
fre
fle
After detecting a strabismus it
must be characterized:
• Direction
• Frequency
• Magnitude
• Laterality
e
• comitance
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Method
Unilateral Cover
Characterization of the
strabismus
Direction
If upon covering the right eye, the left eye moves…
There is a strabismus
Vertical movement...
Horizontal movement...
upwards
Hypotropia
Exotropia
downwards
Hypertropia
Endotropia
inwards
outwards
Method
Characterization of the
strabismus
If upon covering the right eye,
The left eye moves vertically UPWARDS
Direction
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e
fle
Unilateral Cover
Hypotropia LE
Method
Unilateral Cover
Characterization of the
strabismus
Direction
fod
e
foi
If when covering the right eye, the left eye moves vertically UPWARD
Hypertropia LE
Method
Unilateral Cover
Characterization of the
strabismuc
Direction
If when covering the right eye,the left eye moves horizontally OUTWARD
fre
fle
e
Endotropia LE
Method
Unilateral Cover
Characterization of the
strabismus
Direction
If when covering the right eye, the left eye moves horizontally INWARD
fre
fle
e
Exotropia LE
Method
Unilateral Cover
Characterization of the
strabismus
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Frequency
Method
Unilateral Cover
Characterization of the
strabismus
Frequency
Given a concrete distance we can find that..
A strabismus is present
Always
Constant
strabismus
Greater probability of
Sensory adaptations
(amblyopías, eccentric fixations,
suppressiones, anomalous correspondence)
Sometimes
Intermitent
strabismus
Binocular vision is present
sometimes
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Method
Unilateral Cover
Characterization of the
strabismus
Magnitude
In order to evaluate the magnitude of the deviation we are going to rely
on the alternating cover test with prisms.
The alternating cover test consists in passing the occluder from
one eye to the other without allowing the possibility of fusion. In
this moment we evaluate the type of movement.
The placement of the situated prisms in the appropriate position
will make the movement cease. The prismatic quantity that
makes the movement cease during the alternating cover test
tells of the total measurement of the deviation.
Method
Characterization of the
strabismus
Unilateral Cover
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Magnitude
But what does the prism do?
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When facing an ocular deviation, the deviated eye,
when incited to fixate due to the covering of the fixating
eye (supposing central fixation), will have to realize
movement in order to direct its fovea towards the
object of interest.
The prism corresponding to the magnitude of the
deviation makes it so that the eye does not need to
move towards the object of interest since through the
prism the image of this object has been situated along the
visual axis
Method
Characterization of the
strabismus
Unilateral Cover
Magnitude
But what does the prism do?
fre
fre
fle
Movement during the cover test
fle
Method
Characterization of the
strabismus
Unilateral Cover
Magnitude
But what does the prism do?
fre
fle
fre
fre
fle
That prism that
ceases the
Occluder
movement provides
us with the
magnitude of the
deviation
Occluder
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Method
Unilateral Cover
Characterization of the
strabismus
The base of the prism depends of the type of deviation
ENDODEVIATIONS:
Temporal bases (BT)
EXODEVIATIONS:
Nasal bases (BN)
Magnitude
Method
Unilateral Cover
Characterization of the
strabismus
Magnitude
In vertical deviations, it depends on the eye on which the prism is situated
Left HYPOTROPIA:
Superior bases (SB) in front of the left eye
Inferior bases (IB) in front of the right eye
Left HYPERTROPIA:
Superior bases (SB) in front of the right eye
Inferior bases (IB) in front of the left eye
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Method
Unilateral Cover
Characterization of the
strabismus
Laterality
The strabismic eye can always be the same or it can be both in an alternating
pattern
The strabismic eye can be…
Always the same
Unilateral
strabismus
Greater probability of
Sensory adaptations
(amblyopias, eccentric fixations,
suppressiones, anomalous correspondence)
The right or
left eye
Alternating
strabismus
Method
Unilateral Cover
Characterization of the
strabisums
Always the same
Laterality
Unilateral strabismus
The deviated eye is always the LE
Method
Unilateral Cover
Characterization of the
strabismus
Laterality
Alternating strabismus
The deviated eye can be one or the other
Method
Unilateral Cover
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Method
Unilateral Cover
Characterization of the
strabismus
INcomitance
It is a characteristic of the ocular deviations that is related to their etiology.
It will be evaluated in various ways:
• Quantifying the deviation depending on the vantage point.
• Evaluating the existence of limitations in versions or ductions.
Method
Unilateral Cover
Characterization of the
strabismus
Incomitance
Deviation
Comitance
• Differences inferior to 7D in distinct vantage points
Incomitance
• Differences superior to 7D in distinct
vantage points
• There is no limitation in versions or in ductions
• There is limitation in versions and/or
in ductions
Method
Unilateral Cover
Characterization of the
strabismus
Incomitance
Supra dextroversion
Supraversion
Supra levoversion
Dextroversion
Primary position
Levoversion
Infra dextroversion
Infraversion
Infra levoversion
Method
Method
Through occlusion and analysis of the observations
Objective
Unilateral Cover
Detection of strabismus
Cover - Uncover
Detection of phoria
Alternating Cover Test
Evaluation of the totality of the
deviation
Method
Cover - Uncover
Detection of phoria
Cover an eye and observe if uncovering it results in movement of any
type
fre
fle
Movement?
e
Method
Cover - Uncover
Detection of phoria
Observe if any movement of the eye that is covered is
produced
fre
fle
After the occluder is eliminated the fixation
stimulus and the eye are situated in the
passive position.
The evaluation of the passive position
Determines the existence of a phoria.
e
If when taking away the occluder the
covered eye moves, we are facing a phoria.
Method
Cover - Uncover
Detection of phoria
If when covering the right eye, it takes a passive position so that when it is
uncovered it needs to move in order to fixate, we are faced with a phoria.
fre
fle
e
fre
fle
e
The presence of movement reveals a phoria
fre
fle
e
Method
Cover - Uncover
Detection of phoria
If the uncovered eye moves, we are faced with a phoria
fre
fle
After detecting a phoria these factors
must be characterized:
• Direction
• Magnitude
• Comitance
e
Method
Cover - Uncover
Characterization of a
phoria:
• Direction
• Magnitude
• Comitance
Method
Cover - Uncover
Characterization of the phoria
Direction
When covering the right eye, it takes its passive position behind the occluder
When uncovering we can find that…
It moves in a
horizontal sense
It does not move
upward
inward
Orthophoria
Hypophoria
Exophoria
downward
outward
Hyperphoria
Endophoria
It moves in a
vertical sense
Method
Cover - Uncover
Characterization of the phoria
If when uncovering the right eye, It moves horizontally…
fre
fle
e
outwards
Endophoria
Direction
Method
Cover - Uncover
Characterization of the phoria
If when uncovering the right eye, it moves horizontally…
fod
foi
e
inward
Exophoria
Direction
Method
Cover - Uncover
Characterization of the phoria
fre
e
fle
If when uncovering the right eye, it moves vertically…
upward
Hypophoria
Direction
Method
Cover - Uncover
Characterization of the phoria
fod
e
foi
If when uncovering the right eye, it moves vertically…
downward
Hyperphoria
Direction
Method
Method
Through occlusion and analysis of the observations
Objective
Unilateral Cover
Detection of strabismus
Cover - Uncover
Detection of phoria
Alternating Cover Test
Evaluation of the totality
of the deviation
Method
Method
Alternating Cover Test
Evaluation of the totality of the
deviation
Pass the occluder from one eye to the other repeatedly without allowing fusion.
Evaluate the existence of movement in the eye that is fixating.
fre
fle
e
Movement?
Method
Method
Alternating Cover Test
Evaluation of the totality of the
deviation
Observe if movement of the eye that is uncovered is produced.
fre
fle
After the occluder is eliminated the fixation
Stimulus and the eye are situated in passive
positions
Not allowing fusion to be produced makes the
Movement being observed clearer
e
Phoria and tropia are not differentiated
Method
Method
Evaluation of the totality of the
deviation
Alternating Cover Test
If when passing the occluder from one eye to another the uncovered eye moves…
fre
fle
e
fre
fle
e
fre
fle
e
Method
Method
Alternating Cover Test
Evaluation of the totality of the
deviation
If the uncovered eye moves, the type of deviation* will have to be characterized:
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• Direction
• Phoria or tropia
• Magnitude
• Comitance
e
(*See the characteristics in prior sections)
Exercises
Self-evaluation
Exercises
Give a name to the following conditions according to the observations
realized during the cover test.
Exercises
Example 1.
Exercises
Example 1. Orthotropia
Exercises
Example 2.
Exercises
Example 2. Constant Endotropia LE
Exercises
Example 3.
Exercises
Ejemplo 3. Constant Exotropia LE
Exercises
Example 4.
Exercises
Example 4. Constant Hypotropia LE
Bibliography
Bibliography
Bibliography
• Von Noorden GK. Atlas de estrabismos.
Madrid: Mosby-Ciagami, 1997
• Caloroso EE, Rouse MW. Tratamiento clínico del estrabismo.
Madrid: Ciagami, 1999
• Hugonnier R. Hugonnier S. Estrabismos heteroforias y parálisis oculomotrices.
Barcelona: Toray-Masson, 1977
• Prieto-Díaz J, Souza-Dias C. Estrabismo (5ª ed.).
Buenos Aires : Ediciones Científicas Argentinas, 2005
• Von Noorden GK , Helveston EM. Estrabismos. Decisiones clínicas.
Madrid: Ciagami, 1997
• Borràs MR et al. Visión binocular. Diagnóstico y tratamiento.
Barcelona. Ediciones UPC, 1996
• Computer program OSP2