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
What is a phoria?
UtilityWhat is a strabismus?
6
7
15
Material 18
Method 19
Theme 6: Cover test
Description
MethodUnilateral Cover
19
20
21Characterization of strabismus 28
Direction
Frequency
Magnitude
Laterality
comitance
30
36384549
Theme 6: Cover test
Description
Cover – Uncover 53
54Characterization of strabismus 58
Direction
Magnitudecomitance
Cover – Alternating 64
595959
Theme 6: Cover test
Self-evaluation 69
Bibliography 79
Theme 6: Cover test
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
axis
flefreWe are facing a strabismus when both eyes do not simultaneously direct their visual axes onobject of interest….
What happens when an ocular deviation isproduced?
What is a strabismus
Utility
fle fre
In this case, what is called a Normal Sensory Correspondence (NSC) exists.
When binocular vision exists, the object of interest stimulates both foveassimultaneously, thereby achieving a fusion of the image on a corticallevel.
What is a strabismus
Utility
fle fre0
fle + fre = + = Confusion
fle + O = + = Diplopia
Facing an ocular deviation, the following effects could be produced:
• diplopia
• confusion
What is a strabismus
Utility
fle fre0
Facing these possibilities and uncomfortable effects,the visual system can respond by trying to avoidthem through:
• Abnormal retinal correspondence• Suppresion• Eccentric fixation• Torticollis
What is a strabismus?
Utility
fle fre0
ARC
Abnormal retinal correspondence
The fovea of the deviated eyewill not correspond with fixating eye,thereby resulting in the binocular function, point “0”.
What is a strabismus?
Utility
fle fod0
Suppression
The image that prevails is that whichonly pertains to the directing eye.
What is a strabismus?
Utility
fle fre0
Occlud-er
Eccentric fixation
It happens when the deviated eye, in a monocular way, prefers to look at the object of interest with a distinct point of thefovea
What is a strabismus?
Utility
Paralysis of the OS from the RE
Torticollis
There are different types of strabismus in which diplopia and confusion only appear in certain “sight” positions
This can make the patient present aninclination of the head in order to maintain,“in a habitual way”, sight in the position of greatest comfort.
What is a strabismus?
Utility
Habitual position
Ocular deviation
The visual axes of both eyes are directedat 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
A phoria is a latent deviation.
This deviation becomes apparent after the elimination of the fusion stimulus(occluder, Maddox rod, prisms...)
What is a phoria?
Utility
flefre
c
An endophoria utilizes the negative fusionalvergence (NFV) in order to bring bothvisual axes onto the object of interest.
NFC
The type of fusional convergence to utilize depends on the type of phoria
What is a phoria?
Utility
flefre
c
An exophoria utilizes the positive fusionalvergence (PFV) in order to bring the visual axes onto the object of interest.CFP
What is a phoria?
Utility
• Accomodative card
• Occluder
• Optotype from distance
• Prisms
Material
Cover - Uncover
Alternating Cover Test
Unilateral Cover
Detection of phorias
Evaluation of the totality of thedeviation
Detection of strabismus
Objective
By covering one of the two eyes and analyzing what is observed
Method
Cover - Uncover
Alternating Cover Test
Unilateral Cover
Detection of phorias
Evaluation of the totality of the deviation
Detection of strabismus
Objective
By covering one of the two eyes and analyzing what is observed
Method
Unilateral Cover Detection of strabismus
Cover and uncover an eye, observing if in the other eye some movement of fixation is produced
e
flefre
Movement?
Method
If upon covering the right eye…
1. There is No movement of the left eye
The absence of movement tells of orthotropia (absence of strabismus)
e
flefre
e
flefre
Hide the left eye
Unilateral Cover
Method
Detection of strabismus
1. There is no movement
Observe whether movement of the uncovered eye
2. There is movement
• Possible Orthotropia (there is no strabismus)
• Tropia (there is strabismus)e
flefre
Movement?
Unilateral Cover
Method
If upon hiding the right eye…
1. There is No movement of the left eye
e
flefre
e
flefre
Hide the left eye
The absence of movementtell of orthotropia (absence of strabismus)
Unilateral Cover
Method
If upon covering the right eye…
2. There is movement of the left eye
The presence of movements tells of strabismus
e
flefre
Indicates that the left eye was deviated
Unilateral Cover
Method
e
flefre
If upon hiding the right eye…
2. There is movement of the left eye
Endotropia LEe
flefre
It indicates that the left eye was deviated
e
flefre
Unilateral Cover
Method
If upon covering the right eye …
2. There is movement of the left eye
After detecting a strabismus itmust be characterized:
• Direction• Frequency• Magnitude• Laterality• comitance
Unilateral Cover
Method
e
flefre
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Unilateral Cover
Method
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Unilateral Cover
Method
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Unilateral Cover
Method
Characterization of the strabismus
If upon covering the right eye, the left eye moves…
Vertical movement... Horizontal movement...
inwards
Endotropia outwards
Exotropia
There is a strabismus
upwards
downwards Hypertropia
Hypotropia
Unilateral Cover Direction
Method
If upon covering the right eye,The left eye moves vertically UPWARDS
Hypotropia LE
e
flefre
Characterization of the strabismus DirectionUnilateral Cover
Method
If when covering the right eye,the left eye moves vertically UPWARD
Hypertropia LEe
foi
fod
Characterization of the strabismus DirectionUnilateral Cover
Method
the left eye moves horizontally OUTWARDIf when covering the right eye,
Endotropia LEe
flefre
Characterization of the strabismuc DirectionUnilateral Cover
Method
the left eye moves horizontally INWARDIf when covering the right eye,
Exotropia LEe
flefre
Characterization of the strabismus DirectionUnilateral Cover
Method
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Unilateral Cover Characterization of the strabismus Frequency
Method
Given a concrete distance we can find that..
Always Sometimes
A strabismus is present
Constantstrabismus
Greater probability of Sensory adaptations(amblyopías, eccentric fixations,suppressiones, anomalous correspondence)
Intermitentstrabismus
Binocular vision is presentsometimes
Unilateral Cover Characterization of the strabismus Frequency
Method
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• comitance
Unilateral Cover
Method
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.
Unilateral Cover Characterization of the strabismus Magnitude
Method
But what does the prism do?fle
freWhen 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 realizemovement in order to direct its fovea towards theobject 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 theprism the image of this object has been situated along thevisual axis
Unilateral Cover Characterization of the strabismus Magnitude
Method
But what does the prism do?
frefle
fre fle
Movement during the cover test
Unilateral Cover Characterization of the strabismus Magnitude
Method
That prism that ceases themovement providesus with the magnitude of thedeviation
fle fre fle
Occluder
fre
Occluder
Unilateral Cover Characterization of the strabismus Magnitude
But what does the prism do?
Method
flefre
The base of the prism depends of the type of deviation
ENDODEVIATIONS:
Temporal bases (BT)
EXODEVIATIONS:
Nasal bases (BN)
Unilateral Cover Characterization of the strabismus Magnitude
Method
In vertical deviations, it depends on the eye on which the prism is situated
Left HYPOTROPIA:
Superior bases (SB) in front of the left eyeInferior bases (IB) in front of the right eye
Left HYPERTROPIA:
Superior bases (SB) in front of the right eyeInferior bases (IB) in front of the left eye
Unilateral Cover Characterization of the strabismus Magnitude
Method
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Unilateral Cover
Method
The strabismic eye can always be the same or it can be both in an alternating pattern
Always the same The right or left eye
The strabismic eye can be…
Unilateralstrabismus
Greater probability of Sensory adaptations(amblyopias, eccentric fixations,suppressiones, anomalous correspondence)
Alternating strabismus
Unilateral Cover Characterization of the strabismus Laterality
Method
Always the same
The deviated eye is always the LE
Unilateral strabismus
Unilateral Cover Characterization of the strabisums Laterality
Method
The deviated eye can be one or the other
Alternating strabismus
Unilateral Cover Characterization of the strabismus
Method
Laterality
Characterization of the strabismus:
• Direction
• Frequency
• Magnitude
• Laterality
• Comitance
Unilateral Cover
Method
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.
Unilateral Cover Characterization of the strabismus
INcomitance
Method
Comitance Incomitance
Deviation
• Differences inferior to 7D in distinct vantage points • Differences superior to 7D in distinct vantage points
• There is no limitation in versions or in ductions
• There is limitation in versions and/orin ductions
Unilateral Cover Characterization of the strabismus
Incomitance
Method
Unilateral Cover
Method
Characterization of the strabismus
Incomitance
Supraversion
Primary position
InfraversionInfra dextroversion Infra levoversion
Supra dextroversion Supra levoversion
Dextroversion Levoversion
Cover - Uncover
Method
Alternating Cover Test
Unilateral Cover
Detection of phoria
Evaluation of the totality of thedeviation
Detection of strabismus
Objective
Through occlusion and analysis of the observations
Method
Cover - Uncover Detection of phoria
Cover an eye and observe if uncovering it results in movement of any type
e
flefre
Movement?
Method
Cover - Uncover Detection of phoria
Observe if any movement of the eye that is covered is produced
e
flefre 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.
If when taking away the occluder the covered eye moves, we are facing a phoria.
Method
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.
The presence of movement reveals a phoria
e
flefre
e
flefre
Cover - Uncover Detection of phoria
e
flefre
Method
If the uncovered eye moves, we are faced with a phoria
After detecting a phoria these factorsmust be characterized:
• Direction• Magnitude• Comitance
Cover - Uncover Detection of phoria
e
flefre
Method
Characterization of a phoria:
• Direction
• Magnitude
• Comitance
Cover - Uncover
Method
When covering the right eye, it takes its passive position behind the occluder
When uncovering we can find that…
It moves in a vertical sense
upward
downward
Hyperphoria
Hypophoria
It moves in a horizontal sense
inward
Endophoria
outward
Exophoria
It does not move
Orthophoria
Cover - Uncover Characterization of the phoria Direction
Method
If when uncovering the right eye,It moves horizontally…
e
flefre
outwardsEndophoria
Cover - Uncover Characterization of the phoria Direction
Method
If when uncovering the right eye,it moves horizontally…
e
foifod
inwardExophoria
Cover - Uncover Characterization of the phoria Direction
Method
If when uncovering the right eye, it moves vertically…e
flefre
upwardHypophoria
Cover - Uncover Characterization of the phoria Direction
Method
If when uncovering the right eye, it moves vertically…
downwardHyperphoria
e
foi
fod
Cover - Uncover Characterization of the phoria Direction
Method
Cover - Uncover
Method
Alternating Cover Test
Unilateral Cover
Detection of phoria
Evaluation of the totalityof the deviation
Detection of strabismus
Objective
Through occlusion and analysis of the observations
Method
Method
Pass the occluder from one eye to the other repeatedly without allowing fusion.
Evaluate the existence of movement in the eye that is fixating.
e
flefre
Movement?
Alternating Cover Test Evaluation of the totality of thedeviation
Method
Method
Observe if movement of the eye that is uncovered is produced.
e
flefre After the occluder is eliminated the fixationStimulus and the eye are situated in passivepositions
Not allowing fusion to be produced makes theMovement being observed clearer
Phoria and tropia are not differentiated
Alternating Cover Test Evaluation of the totality of thedeviation
Method
Method
If when passing the occluder from one eye to another the uncovered eye moves…
Alternating Cover Test Evaluation of the totality of thedeviation
e
flefre
e
flefre
e
flefre
Method
Method
If the uncovered eye moves, the type of deviation* will have to be characterized:
• Direction
• Magnitude• Comitance
Alternating Cover Test Evaluation of the totality of the deviation
e
flefre
• Phoria or tropia
(*See the characteristics in prior sections)
Method
Self-evaluation
Exercises
Give a name to the following conditions according to the observationsrealized 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
Exercises
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
Bibliography
• Computer program OSP2