BVP - Strabismus Assessment III - Week 12

Question 1

List the 6 sensory aspects of strabismus.

Answer 1

Visual acuity
Fixation
Suppression
Stereopsis
Motor fusion
Anomalous correspondence

Question 2

Where is fixation on the retina in normal acuity patients? what about with amblyopia (2)?

Answer 2

It is central in normal patients - on the macula

In amblyopia, it may be central or unsteady (but around the macula)

Question 3

Describe eccentric fixation and how it may occur (2). What is the cause?

Answer 3

Ocassionally the macula of a deviating eye does not have motor superiority
The fixation is steady by eccentric
The cause is unknown

Question 4

Can eccentric fixation be seen with casual observation? Explain.

Answer 4

Deviation is 1-3 degrees so cant be casually observed

Question 5

How can the fixation of a patient be assessed? Do these patients (with eccentric fixation) respond to treatment such as occlusion?

Answer 5

Use the visuoscope on a direct ophthalmoscope (looks like a sniper scope) to assess the steadiness and centrality of fixation
They do not respond to occlusion

Question 6

Describe diplopia and confusion in strabismic amblyopia (esotropic eye). Describe using a house and a tree and the patient’s view.

Answer 6

Consider a house with a tree on its left, the patient fixates the house, the right eye is esotropic.
The house will fall on the macula in the left eye and nasally on the right eye
Diplopia is seen with the house with one central and another being pereived temporally due to the esotropia
The tree falls on the macula of the esotropic eye and so the central house is superimposed by the tree in their view

Question 7

List 4 measures of suppression. What degrees of fusion does it measure (2)? What does it assess exactly?

Answer 7

Worth 4 dot test
Polarised letters or targets
Red filter ladder
Synoptophore
Measures 1st and 2nd degree fusion
Looks at patients ability to perceive input from the non-dominant eye when both eyes are open

Question 8

What kind of phenomenon is suppression and what does this mean?

Answer 8

Is biocular - both eyes are open

Question 9

What typically develops when there is diplopia and confusion? What is its primary function?

Answer 9

The patient develops a suppression scotoma at least as large as the angle of deviation
Primary function is to remove diplopia and confusion

Question 10

Can you have amblyopia without suppression? What about suppression without amblyopia?

Answer 10

Can have suppression without amblyopia

Cannot have amblyopia without suppression

Question 11

Is it possible to pass titmus randot with constant strabismus? What about the fly test?

Answer 11

Is possible with ~10^D ET for fly test

No patient ever passed titmus randot with constant strabismus

Question 12

Can a titmus randot test find the following?
Intermittent esotropia
Alternating esotropia
Exotropia

Answer 12

Will find both intermittent and alternating esotropia

Will often miss exotropia

Question 13

Can a titmus randot test find refractive amblyopia?

Answer 13

No

Question 14

At what age can a titmus randot test be performed?

Answer 14

Age 3+

Question 15

Can all children aged 3+ pass titmus fly? What about randot?

Answer 15

All should be able to pass the fly test if physiologically able
90% and all 4+ should pass randot

Question 16

Around what age do children begin to pass all 9 wirt circles?

Answer 16

8 to 9

Question 17

Does no stereopsis result in no depth perception? Explain (2).

Answer 17

No stereopsis does not result in no depth perception

But does result in reduced depth perception especially up to 3m

Question 18

Define anomalous correspondence.

Answer 18

Rearrangement of the correspondence of the receptors of the deviating eye so that it matches the fixating eye
Results in a palse macula over a region not over the macula

Question 19

What is used to test for anomalous correspondence?

Answer 19

Bagolini lenses

Question 20

Where is anomalous correspondence thought to occur?

Answer 20

It is a ocrtical phenomenon

Question 21

Can anomalous correspondence be central? Explain (2).

Answer 21

Yesd and this may cause diplopia following strabismus surgery

Question 22

Describe bagolini glasses and how they assess anomalous correspondence.

Answer 22

Like a pair of maddox lenses but are clear and oriented at 56 and 135
Patient looks at a torch while wearing them
If a perfect cross is seen, then no AC, but suppression, imperfect crossing, and missing regions can mean tropia or abnormal correspondence

Question 23

What is the best way to remove anomalous correspondence (2)?

Answer 23

Glasses or surgery