VF - Binocular Vision - Fusion and Heterophoria - Week 2

Question 1

Describe how versions can be measured.

Answer 1

A semicircular frame is placed around the patient, and a point on the frame is moved, until they are unable to see/focus it.
They cant turn their head.

Question 2

Describe the pushup method of convergence measurement.

Answer 2

Have them focus on a point in front of them. Bring it closer until they can no longer focus on it.

Question 3

How does a prism bend light? How does this affect the eyes focus?

Answer 3

Light is bent towards the base, so the image appears closer to the apex. Eye must then shift to the apex to keep focus.

Question 4

Define anatomical position of eyes at rest.

Answer 4

17 base beyond parallel.

They are divergent.

Question 5

Define tonic vergence.

Answer 5

Position with normal innervation but no stimulus (in the dark)
Physiological position of rest

Question 6

Define orthophoria.

Answer 6

If active and passive positons of the eye coincide.

Question 7

Define heterophoria.

Answer 7

When the active and passive positions of the eye are different.

Question 8

Name and describe the two kinds of heterophoria.

Answer 8

Exophoria
If the passive position is divergent to the active position.
Esophoria
If the passive position is convergent to the active position.

Question 9

How can the angle of movement be detected?

Answer 9

Have a patient focus at distance, and cover one eye and observe movement.

Question 10

Name 6 anatomical factors for heterophoria.

Answer 10

Size and shae of the orbit.
Anomalies of the muscles, sheaths, and ligaments.
Lesions of ocular motor neural apparatus.

Question 11

Name 5 non-anatomical factors for heterophoria.

Answer 11

General fatigue
Overwork
Excessive use of alcohol/tobacco
Prismatic effect of spectacles

Question 12

How common is heterophoria?

Answer 12

75-90% of general population is heterophoric.

Question 13

Which meridian is the most common for heterophoria?

Answer 13

In the horizontal meridian.

Question 14

Define hyperphoria, hypophoria, and cyclophoria.

Answer 14

Hyper/hypophoria - vertical misalignment

Cyclophoria - eye rotates about the visual axis. Rotation nasally - incyclophoria, temporal rotation - excyclophoria.

Question 15

What fixation distances are used for distance and near phoria?

Answer 15

Distance - 6m

Near - 40cm

Question 16

Is phoria consistent from far through near?

Answer 16

No, it differs at distance vs near.

Question 17

Define physiological exophoria.

Answer 17

Normal exophoria occurring at near distances, relative to far distances.

Question 18

Define compensated phoria and decompensated phoria.

Answer 18

Compensated - heterophoria is asymptomatic, fusional vergence maintains vergence
Decompensated - symptoms are apparent, correction may be needed

Question 19

Name 9 causes of decompensated phoria.

Answer 19

• Excessive use of vision under demanding circumstances
• Inadequate fusion reserves
• Accommodative anomalies - uncorrected hyperopia
• Ametropia
• Poor general health
• Stress
• Old age
• Neurological disorders
• Side effects of medications

Question 20

Name 9 symptoms of decompensated phoria.

Answer 20

Headaches
Aching eyes
Diplopia
Blurred vision
Focusing difficulties
Difficult depth perception
Monocular comfort over binocular
Sore eyes
General irritation

Question 21

Name 7 ways of measuring heterophoria.

Answer 21

– Cover test
– Maddox rod
– Maddox wing
– von Graefe’s method of insuperable prism
– Prentice Card
– Maddox double prism
– Synoptophore