Binocular vision - easier than you think (lecture)

Question 1

The two system approach

Answer 1

Vergence (aiming) system

Accommodation (focusing) system

Question 2

Binocular metaphor for patients to explain two systems

Answer 2

You have to line binoculars up in front of your eyes and then you have to adjust the focus.

In a similar way, we have muscles outside of our eyes that help line our eyes up to point at the object of interest (our vergence system) and muscles inside of our eyes to help adjust the focus to make things clear (our accommodative system).

Question 3

What 3 things do both systems need

Answer 3

1. Stamina
2. Stability
3. Maintenance without fatigue

Question 4

Diagnoses for underactive vs overactive vergence

Answer 4

Underactive: exophoria or convergence insufficiency

Overactive: esophoria or convergence excess

Both: infacility/ spasm

Question 5

Diagnoses for underactive vs overactive accommodation

Answer 5

Underactive: problems with minus or accommodative insufficiency

Overactive: problems with plus or accommodative excess

Both: Infacility/ spasm

Question 6

Most binocular vision problems occur where?

Answer 6

Near- where kids spend most of their time reading/ where adults spend most of their time working.

Distance binocular problems aren’t as much of an issue.

Question 7

“Normal” ranges for near phoria

Answer 7

1 eso - 4 exo

Question 8

“Normal” base out fusional range for near (based on jump vergence not smooth vergence when testing with prism bar)

Answer 8

30/25 (break/recovery)

Question 9

“Normal” base in fusional range for near (based on jump vergence not smooth vergence when testing with prism bar)

Answer 9

12/10 (break/recovery)

Question 10

“Normal” NPC (jump)

Answer 10

10cm, held

Question 11

“Normal” accommodation range

Answer 11

Normal NRA: clears -3.50
Normal PRA: clears +2.00
Cycles on +/- 2.00

Question 12

“Normal” AC/A ratio

Answer 12

accommodative convergence/ accommodation (the amount of convergence measured in prism diopters per diopter change in accommodation)

3:1

Question 13

“Exo problems”

Answer 13

• Distance & Near: Basic Exo
• Near: Convergence Insufficiency
• Distance: Divergence Excess

Question 14

“Eso Problems”

Answer 14

• Distance & Near: Basic Eso
• Near: Convergence Excess
• Distance: Divergence Insufficiency

Question 15

Explain “twice as much petrol in the tank to balance the posture”

Answer 15

The numbers for their fusional ranges need to be double the number of their phoria to balance it out.

Question 16

With the prism bar, what do you always want to measure first?

Answer 16

Divergence first, then convergence

Question 17

NRA or PRA first?

Answer 17

Plus first before minus

Question 18

Vergence disorders involving both eso & exo

Answer 18

Infacility: mainly at near, low positive fusional ranges (BO) and negative fusional ranges (BI)

Inflexibility/ spasm: fatigue or persistence of effects “sticky eyes”

Question 19

Common co-occuring vergence & accommodation diagnoses

Answer 19

Accommodative insufficiency and convergence excess (concern for myopia development and progression)

Accommodative excess and convergence insufficiency.

Question 20

Difficulties diverging often goes hand in hand with

Answer 20

Low PRA (testing how well someone can clear minus, putting the plane of vergence behind the plane of accommodation)

Question 21

Difficulties converging often goes hand in hand with

Answer 21

Low NRA (testing how well someone can clear plus, putting the plane of accommodation behind the plane of vergence)