11. Amblyopia & Strabismus Evaluation

If the pt suppresses, can you do synoptophore testing for AC?

NO - AC is a BINOCULAR state; they must not be suppressing to measure!

How do you perform the IXT control scale?

Step 1: Have pt look in distance and stare at them. If their eye moves out they get a score of 3-5. If there was not an exo in the distance, dissociate them and give them a score of 0-2. Step 2: Have pt look at near and stare at them. If their eye moves out, they get a score of 3-5. If there was not an exo in the distance, dissociate them and give them a score of 0-2.

Is bagolini lenses objective or subjective?

Subjective!

How can you find angle A (anomalous correspondence) from the red lens for correspondence?

Subtract angle S from angle D. Angle D = Angle A + Angle S

If I had the patient in the above example move the deviating eye until they saw the lion in the cage and then I perform a unilateral CT and the eye does move, what does this mean?

Suggests anomalous correspondence

If I had the patient in the above example move the deviating eye until they saw the lion in the cage and then I perform a unilateral CT and the eye does not move, what does this mean?

Suggests that the patient has normal correspondence. (was just a measurement error, so angle D = angle S)

With the Hering-Bielschowsky After image test: f a pt's right eye was tagged with the vertical line (so the strab eye), and the left eye with the horizontal line, and they see the vertical line to the right of center, what kind of diplopia/anomalous correspondence do they have?

Uncrossed AI, Exo

Quiz: You neutralize the eye movement at 40^BO, but when you ask the pt if the lion is in the cage, they say no. They then move the objects to 20^BO. You perform a unilateral CT by dousing the light over the fixating eye, and you see consistent movement at 20^BO. What kind of correspondence do they have?

Unharmonious AC

Normal Correspondence (NC) with ET. What is the Z angle? What is the D angle? what is the S angle?

When I do an objective measurement, CT, I am measuring angle D. S is the subjective response. Pt will tell us when things are aligned (lancaster) No angle A because patient's foveal are linked.

When does a patient with Harmonious AC see single?

With Harmonious AC, the only time the patient sees single is when the eye is turned in the strabismus position. A point and Z point are the same.

Do we need to worry about EF with the Hering-Bielschowsky After image test?

Yes - anytime you make a pt monocular, you have to worry about EF! For this test, we're depending on the fact that we're tagging the fovea, but if they have EF, that won't be true.

With the Hering-Bielschowsky After image test: -If a pt sees a perfect cross, does it always mean they have normal correspondence?

Yes - no matter if the eye moves, or even if they have a large angle strabismus!

Example: If patient is a 6 exo on CT and a 1 Exo on haidinger brushes, what is the true obj angle?

(-6) + (-1) = -7

What questions must be asked in a cases of suspected amblyopia?

* Family history of amblyopia and/or strabismus (ocular history) * Family medical history * Trauma * Onset of problem * Onset of eye turn, (for strabismic cases) * Any previous treatment (what, when, how long, improvement) * Diplopia questions

What is the measurement error with synoptophore?

+/- 3.00^

What does case history and diagnostic testing consist of for an evaluation of strabismus?

- Case History: make sure all comprehensive exam questions are answered - Diagnostic Test Sequence * Refractive Status * Visual Acuity * Monocular Fixation * Deviation Variable * Correspondence * Sensorimotor Fusion

If a patient has diplopia, what questions must be asked?

- Horizontal, vertical, slanted - Distance or near - Both eyes open or one eye open - Able to eliminate by tipping or tilting head - Changes during the day - Changes over time

Synoptophore testing: With the tubes aligned at ortho, place the slide with more or less detail over the deviating eye?

- Less detail (Because more like primary deviation? We don't want the strab eye to fixate extra and force it to move more than in real life.. or help it?)

More details on the IXT control scale.

- Patient must not not have been disassociated for at least 10 minutes before doing test - Have patient focus at a distant target for 30 secs, you watch eyes for signs of exotropia - Next have patient focus on an accommodative target at near for 30 secs, you watch eyes for signs of exotropia - If grade is level 2-0 next cover the right eye for 10 seconds and then remove it, measuring the length of time it takes for fusion to be re-established. The left eye is then occluded and the same procedure is performed - This is done three times at distance then at near. The score is the worse of the three for distance and near. - You end up getting a control scale control for distance and one for near - Over time you can monitor the loss of control (the frequency)

Types of anomalous correspondence: 2. Unharmonious Anomalous Correspondence. What is it?

- The angle of anomaly is less than the objective angle - Considered an incomplete sensory adaptation to the motor misalignment

There are three ways to do a cover test: What does the unilateral cover test - test?

- Used to identify strabismus, (Manifest), from phoria, (latent) - Can watch either eye, but most know what movement is telling you based upon which eye is being covered

There are three ways to do a cover test: What does Prism and Alternate Cover Test, (PACT) do for us?

- What you typically use to measure the deviation in clinic - This will measure the FULL magnitude of the patients deviation, which includes the strabismus, (manifest deviation) and phoria, (latent deviation)

What methods do we have for measuring AC?

- Worth 4-dot - Bagolini Lenses - Red Lens - Hering-Bielschowsky After Image - AI and HB - Synoptophore

Synoptophore testing: What kind of target do we put into the slide holders?

-First degree (e.g. lion in the cage) -Because there are no similar contours, and we don't want them to fuse

What are red flags during the history?

-Problems in school especially reading concerns -Avoidance of near work is a red flag - Lack of coordination - Recent illness - Medications -Goals of patient and parent - Are the goals viable, realistic?

How do you determine which eye/muscle is paretic with Hess-Lancaster? Circles is where the patient should be pointing. X is where the patient is pointing.

-The doctor (standing next to the pt) points to a screen on the wall and creates a circular image. -Whichever eye on the pt is able to see the circle is the fixating eye -The non-fixating eye points an x to where they think it aligns with he circle.

There are three ways to do a cover test: What does Simultaneous Prism Cover Test, (SPCT) do for us?

-This measures the strabismic component under binocular conditions (no phoria involved) *Tells you the amount of just the strabismus.

How do you do a simultaneous prism cover test?

1. Determine fixating eye by the cover-uncover test 2. Quickly and simultaneously place an occluder over the fixating eye, while placing a prism over the deviating eye 3. Watch for movement of the deviating eye, increase the prism until you do not see any movement and then continue until you see reversal of the deviating eye. 4. Record the high neutral prism 5. If the patient has an intermittent strabismus that cannot be measured this way you would record unable on SPCT. 6. SPCT needs to be performed before the PACT

Example of Hess Lancaster displaying a LLR palsy. How do you know which eye is affected and which muscle?

1. Determine which line, the red or the green, is closest to the center in all the scenarios. That is the bad eye. Red light saber will be seen by eye with red filter and vice versa. 2. Look for the box with the greatest difference between the two lines. Picture my own eyes trying to get to that location while remembering which eye has the paresis. That should allow me identify the problem muscle.

Red lens test: How do you determine which eye/muscle is paretic?

1. Determine which square has the largest separation between the red and yellow dots 2. Determine which dot is furthest from the center square. 3. Determine which eye correlates to the dot furthest from the center (that is the paretic eye). Red lens produces the red dot. 4. Superimpose the H pattern over the grid and remember which eye is paretic to determine which muscle is affected.

CT in 9 directions: How do you determine which eye/muscle is paretic?

1. Find the box with he largest numbers. 2. Note which eye is fixating that yields the largest # -> that is the eye that has a paretic muscle. 4. Superimpose the H pattern over the box to determine which muscle is affected. RSO palsy

Case: I perform CT and find a patient has a 20^ Right Esotropia. I perform Worth 4 dot and the patient says they see 2 red and two green dots. We would expect to get uncrossed diplopia or suppression in the right eye. What could yield fusion of the 4 dots in this case?

1. Harmonious AC (using their A point to fuse) 2. They are intermittent, not constant. They are able to fuse.

Snyoptophore testing: Ask the pt if the two objects are superimposed (i.e. "Is the lion in the cage?"). -What does it mean if they say "No"?

1. If see one object only => Suppression (may need to increase light to strab eye and decrease light to good eye) 2. If objects separated => possible AC, OR measurement error 3. Two separate images never fuse => horror fusionis

What is the procedure for performing Hering-Bielschowsky After image test?

1. Occlude the deviating eye 2. Tag the fovea of the fixating eye with a horizontal bar 3. Occlude the fixating eye 4. Tag the fovea of the non-fixating eye with a vertical bar 5. Have the pt stand 1 m away from a wall where you can measure the distance between the two images

What level of stereo target is the Worth Dot?

2nd degree target.

What is the motor theory?

3. Motor theory: Strabismus and AC have same neurological origin and are simultaneous - Eye movements are divided into two types, registered (fusional), non- registered (accommodative) - Registered eye movements lead to changes in correspondence - This explains Co-variation and that UAC is a combination of both these types of eye movements

What distance do we typically stand away from the Haidinger Brush screen?

40 cm

What is the most natural test for AC?

Bagolini lenses - Free space testing - Can be worn over glasses - Each eye has a lens with striations - RE orientated 135 & LE orientated 45 - Testing is done in normal room illumination while shining a transilluminator at the patient. He/she will see images 90 degrees away from orientation of the striations - High percentage of AC found this way

What can the synoptophore be used to measure?

Can be used to angle D and angle S. *Doctor can actively watch the pt's eyes while doing the test *Can control illumination => can brighten the bad eye and dim the good eye to break suppression, if needed

Quiz: You neutralize the eye movement at 40^BO, but when you ask the pt if the lion is in the cage, they say no. They then move the objects to Ortho. You perform a unilateral CT by dousing the light over the fixating eye, and you see consistent movement at Ortho. What kind of correspondence do they have?

Harmonious AC (<D = <A, and <S = 0)

Snyoptophore testing: If I tried moving the arm of deviating eye to neutralize the angle but the patient says that the objects are still separated and I suspect possible AC, what should I do?

Have the *patient* move the target over the deviating eye until the images are superimposed (lion in cage). Once pt reports objects superimposed, perform a unilateral CT by dousing the light in front of the fixating eye.

How can we directly measure angle A?

Hering-Bielschowsky After Image Test (HBAI). After-image testing is the only way to measure angle A. (including Haidinger Brushes.. all other are indirect).

List the ways you can measure AC in order of MOST natural to LEAST natural.

• Bagolini Lenses • Worth 4-Dot • Red Lens • Synoptophore • Hering-Bielschowsky After-Image • After-Image with Haidinger Brushes (AI HBr)

40 year old male with 20 R hyper, Vertical worse in Left Gaze, Vertical worse in Right Head Tilt

RSO palsy

Red lens test for correspondence is not the same test as for concomitancy. How do you measure objective angle?

1. Place a red lens and vertical prism (~6 BU or BD) over the "normal" non-strabismic eye 2. Have the patient fixate at a distant white light 3. *Add horizontal prism over the deviating eye until patient reports the two dots are aligned* (the steps for measuring the subj. angle) Then to get the objective angle, we take away the red lens and the vertical prism (and keep the horizontal prism in place) 3. Perform alternating cover test. (with the horizontal prism in place and see if now under monocular conditions if we need to add more or less prism).

Red lens test for correspondence is not the same as the test for concomitancy. What is the procedure for measuring subjective angle?

1. Place a red lens and vertical prism (~6 BU or BD) over the "normal" non-strabismic eye 2. Have the patient fixate at a distant white muscle light 3. *Add horizontal prism over the deviating eye until patient reports the two dots are aligned*

Hess-Lancaster: Explain how it works with red and green light sabers.

1. Pt has red green glasses. The red filter will be able to see the red light and the green filter will be able to see a green light. 2. When the red filter is over OD and the doctor points a red light onto the screen, the OD is fixating. The OS points the green light where the pt thinks they align. This is testing the OS.

What are the three types of fusion?

1. Sensory fusion- the images seen by each eye are integrated into a single perceptual image (see singly) 2. Motor fusion- disparate retinal images leading to the two eyes to move to gain fusion. The eyes maintain their corresponding retinal points. (fovea to fovea) 3. Anomalous Motor Fusion (fovea to AC point)

How does AC develop? This process is not completely known, competing theories due to variability in testing and therapy of AC. Each theory explains some aspect of AC development What are three theories?

1. Sensory theory 2. Innate theory adaptation 3. Motor theory

What is the sensory theory?

1. Sensory theory: Strabismus develops first then the AC - AC is an attempt to regain some binocularity by shifting the visual direction to account for the strabismus - This can explain the depth of AC and HAC but not UAC *Why would there only be a partial adaptation?

What is the innate theory?

2. Innate theory: AC develops first then the strabismus develops as an adaptation - With this theory all tx is ineffective, and only produces anomalous motor fusion the detectors are not treated

What is covariation?

A patient with exotropia may have different level of correspondence depending upon the alignment of their eyes, the motor theory explains this phenomena. - When the eye is turned out the patient has AC - When the eyes are aligned the patient has NC - Important to note the alignment of the eyes when testing exotropes

If Dm=0 E=4 Nasal, what is Dt?

True obj angle = CT + EF True obj angle = 0 + (+4) True obj angle is +4. This is a case where CT did not show any deviation bc the patient was using an eccentric fixation point to view straight ahead, therefore their eye did not need to move with the alt. CT. Need to perform a different test to determine if EF is present.

What are some possible reasons for AC adaptation?

AC may be an adaptation to eliminate diplopia and or confusion

Remember eccentric fixation can have an impact on all of your testing. Who should we test EF on?

All strabismic patient's!

What is paradoxical I? (just know it occurs after surgery)

Angle A is greater than angle D -(S opposite direction to D) -S is greater than zero.

Synoptophore testing: 3. Ask if the pt sees both targets (you may need to alternately douse the lights over each eye in order for them to see each target). 4. Perform an alternating CT by alternating the dousing, and moving the arm of the deviating eye until you neutralize the eye movements (no longer see any movement). What angle is this?

Angle D

What angles will equal each other in Harmonious AC?

Angle D will equal angle A -Angle S will be 0

What will be the relationship between angles in Unharmonious AC?

Angle D will not Equal Angle A. Angle D will be greater than angle S (angle S will not be zero)

What is paradoxical II? (just know it occurs after surgery)

Angle s is greater than angle D. -A is opposite direction to D -Angle A is greater than zero.

If you see movement while the pt is reporting fusion then the patient more than likely is experiencing what kind of correspondence?

Anomalous correspondance.

If a pt's right eye was tagged with the vertical line (so the strab eye), and the left eye with the horizontal line, and they see the vertical line to the left of center, what kind of diplopia/anomalous correspondence do they have?

Crossed after-image, so Eso (+)

Ocular health is important.

Do not make an "official" diagnosis of functional amblyopia and or strabismus without first dilating the patient and doing a thorough exam of the retina and macular areas.

What is the equation for calculating the amount of EF when testing using Haidinger Brush?

EF (pd) = Separation target and image (cm) / Distance from screen (meters)

Haidinger Brush: If my patient is 40 cm away from the screen and indicates that the brush is 25mm to the left of the center of the grid when using his/her right eye, what is the amount of EF and the direction?

EF = separation (cm)/ distance (meters) EF = 2.5cm / 0.4m EF = 6.25pd Nasal EF If the brush is to the left, this tells us the fovea is to the right and the EF point is to the left which is nasal.

- How does EF affect cover test measurement

EF hides some angle deviation that cannot be seen on CT. True obj angle = CT (measured obj angle) + EF * Eso, BO, Nasal + * Exo, BI, Temporal - § <Dt=<Dm+<E

T or F: AC is the same thing as EF

False!!! AC does not equal EF. -Eccentric Fixation is a Monocular event, measured monocularly -Anomalous Correspondence is a Binocular event, measured binocularly

T or F. Random (global) dot and Randot (local) are absolute measures of stereopsis.

False. Other tips: -The amount of stereopsis should correlate with your cover test. -Don't just write the number down and not look at it again.

T or F: Angle D = Angle A + Angle S

True.

If you do NOT see movement while the patient is reporting fusion, then the patient more than likely is experiencing what kind of correspondence?

Normal correspondance.

Location of anomaly point defines type of AC.

PAC1 and 2 are post surgery, that's all I have to know.

Snyoptophore testing: Ask the pt if the two objects are superimposed (i.e. "Is the lion in the cage?"). -What does it mean if they say "Yes"?

Possible NC (<D = <S)

What is the definition of Anomalous Correspondence?

Sensory anomaly seen in strabismus. The fovea of the fixating, (non- strabismic, good) eye and a non-foveal point of the non-fixating, (strabismic, bad)eye are "linked" Binocular only!!

With the Hering-Bielschowsky After image test: What will the pt see on this test if they have covariation with a strabismic right eye?

Sometimes normal cross, and sometimes vertical line (right eye) to the right (uncrossed after-image/Exo(-))

T or F. A constant strabismus will not have any global stereo.

True. They have to have bifoveal fixation to see global. Local stereo with randot is a poor chose of stereo.

Types of anomalous correspondence: 1. what is harmonious correspondence?

The brain's complete adaptation to the eyes abnormal position. - The angle of the visual direction of the two retinas is equal to the objective angle of strabismus. - Thought to be a complete adaptation of the motor component of the sensory problem. - Results in no diplopia as long as the eyes are aligned in the patient's strabismic posture

Review: Which eye is the "bad eye" in hess lancaster?

The eye that is closest to the center. (this is opposite of the red-lens test because it is with the point of view of the patient and not the doctor).

In order to determine if the above patient has 1. AC or 2. Intermittent ET, we perform unilateral cover test. Which eye would we cover?

The left eye. Right esotropia, cover the left eye to see if the right picks up fixation.