Projection in Heterotropia

Question 1

What is the principle visual direction (PVD)?

Answer 1

The fovea has the choice in direction

Question 2

What is heterotropia?

Answer 2

A condition where one or other visual axis isn’t directed towards the fixation point

Question 3

What is monocular diplopia?

Answer 3

Diplopia from one eye because of anomalies of the ocular media which disappears when looking through a pinhole. When ocular media is the issue it means light may not refract uniformly so two or more retinal points may receive the same image (‘polyopia’). If it is of a sensory origin it will persist even through a pinhole (but this is rare).

Question 4

What do you need to know to make a presumptive diagnosis of binocular diplopia?

Answer 4

• Frequency of occurrence
• Constant or transient?
• Whether distance between images up or down in different directions of gaze or with different head positions

Question 5

What is fixation switch diplopia?

Answer 5

A random switch in fixation preference in strabismic diplopia who don’t alternate spontaneously leading to diplopia e.g. after surgery or in a change of angle of anomaly or normalisation of retinal correspondence.

Question 6

What is binocular triplopia?

Answer 6

A combination between monocular and binocular diplopia

Question 7

If someone experiences binocular diplopia in absence of strabismus or history, how are they experiencing diplopia?

Answer 7

From awareness of physiological diplopia

Question 8

What is confusion?

Answer 8

The stimulation of corresponding points in the 2 eyes by different objects. It’s rarely reported so can get confusion with diplopia.

Question 9

Is esotropia homonymous or heteronymous? Is it crossed or uncrossed?

Answer 9

Uncrossed
Homonymous (2nd image on same side as the strabismus)

Question 10

Is exotropia homonymous or heteronymous? Is it crossed or uncrossed?

Answer 10

Crossed
Heteronymous (2nd image is on the opposite side to the strabismus)

Question 11

In hypertropia is the image projected inferiorly or superiorly?

Answer 11

Inferiorly (stimulates superior retina)

Question 12

In hypotropia is the image projected inferiorly or superiorly?

Answer 12

Superiorly (stimulates inferior retina)

Question 13

What is suppression?

Answer 13

Mental inhibition of visual sensations from deviated eye

Question 14

What is foveal suppression?

Answer 14

Suppression of the fovea that is central and thus eliminates confusion

Question 15

What is nasal/temporal suppression?

Answer 15

Peripheral suppression that eliminates diplopia

Question 16

What is muscular asthenopia?

Answer 16

Eye strain

Question 17

What is a fixation point scotoma?

Answer 17

Foveal suppression

Question 18

How many scotomas would someone suppressing typically have?

Answer 18

2; one for fixation point scotomas and one to suppress periphery area

Question 19

Are scotomas limited to the deviating eye?

Answer 19

No; they can be suppressed in one eye and the completed by the non-suppressed portion from the field of vision in the other eye

Question 20

What is ignoring?

Answer 20

Psychological level where disregarding the 2nd diplopic image