BLOCK 1: Clinical Exams

transcript

•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?

Material 18

Method 19

Theme 6: Cover test

Description

MethodUnilateral Cover

21Characterization of strabismus 28

Direction

Frequency

Magnitude

Laterality

comitance

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

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.

Utility

fle fre0

fle + fre = + = Confusion

fle + O = + = Diplopia

Facing an ocular deviation, the following effects could be produced:

• diplopia

• confusion

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

Abnormal retinal correspondence

The fovea of the deviated eyewill not correspond with fixating eye,thereby resulting in the binocular function, point “0”.

Utility

fle fod0

Suppression

The image that prevails is that whichonly pertains to the directing eye.

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

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.

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

An endophoria utilizes the negative fusionalvergence (NFV) in order to bring bothvisual axes onto the object of interest.

The type of fusional convergence to utilize depends on the type of phoria

What is a phoria?

Utility

flefre

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

Unilateral Cover

Detection of phorias

Evaluation of the totality of the deviation

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

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)

flefre

Hide the left eye

Unilateral Cover

Method

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

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

flefre

Indicates that the left eye was deviated

Unilateral Cover

Method

flefre

If upon hiding the right eye…

Endotropia LEe

flefre

It indicates that the left eye was deviated

flefre

Unilateral Cover

Method

If upon covering the right eye …

After detecting a strabismus itmust be characterized:

• Direction• Frequency• Magnitude• Laterality• comitance

Unilateral Cover

Method

flefre

Characterization of the strabismus:

• Direction

• Frequency

• Magnitude

• Laterality

• Comitance

Unilateral Cover

Method

• Direction

• Frequency

• Magnitude

• Laterality

• comitance

Unilateral Cover

Method

• 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

flefre

Characterization of the strabismus DirectionUnilateral Cover

Method

If when covering the right eye,the left eye moves vertically UPWARD

Hypertropia LEe

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

Method

• 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

• 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

Method

But what does the prism do?

frefle

fre fle

Movement during the cover test

Method

That prism that ceases themovement providesus with the magnitude of thedeviation

fle fre fle

Occluder

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)

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

Method

• 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

• 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.

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

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

Unilateral Cover

Detection of phoria

Evaluation of the totality of thedeviation

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

flefre

Movement?

Method

Observe if any movement of the eye that is covered is produced

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

flefre

Method

If the uncovered eye moves, we are faced with a phoria

After detecting a phoria these factorsmust be characterized:

• Direction• Magnitude• Comitance

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…

flefre

outwardsEndophoria

Method

If when uncovering the right eye,it moves horizontally…

foifod

inwardExophoria

Method

If when uncovering the right eye, it moves vertically…e

flefre

upwardHypophoria

Method

If when uncovering the right eye, it moves vertically…

downwardHyperphoria

Method

Cover - Uncover

Method

Unilateral Cover

Detection of phoria

Evaluation of the totalityof the deviation

Objective

Through occlusion and analysis of the observations

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.

flefre

Movement?

Alternating Cover Test Evaluation of the totality of thedeviation

Method

Observe if movement of the eye that is uncovered is produced.

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

Method

If when passing the occluder from one eye to another the uncovered eye moves…

flefre

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

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

• 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

BLOCK 1: Clinical Exams

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