2. Learning Objectives
Describe Binocular Single Vision
List the instruments needed for Worth 4-dot Test
Detail the step by step procedure for Worth 4-dot Test
Interpret the patient’s responses
3. Binocular Single Vision(BSV)
Binocular Single Vision (BSV) is the ability to use both
eyes to create a single, common sight or vision
Worth 4-dot test is used to assess the binocular vision in a
patient
4. Worth 4 Dot test-Purpose
To Determine how a patient uses his/her eyes together
There are three possible states: Fusion, Suppression, Diplopia
5. Normal state of vision
Three possible states
Fusion
• The normal
condition of eye
muscles.
• In this case
orthophoria is
present.
• The patient is able
to fuse the images.
Suppression
• If the brain ignores
an image from any
one of the eyes,
suppression occurs.
• The patient may
have right/left or
alternate
suppression
Diplopia
• When the brain is
not able to fuse the
images from each of
the eyes into a
single image,
diplopia occurs
• The patient will see
double images
6. Who needs Worth Four Dots Test
• - Headache
- Eye Strain
- Watering
Asthenopic
symptoms
• - Symptoms associated with
close work
Occasional Diplopia
• Squint
Strabismus
7. What to communicate?
Explain the patient that you are going to check the
binocular vision
You will be shown some lights
You have to tell me how many lights you see and
their position
9. Preparation
Perform the test with low illumination/Light
Fix the distance target at 6 m
Wait for the patient to wear the red and green glasses
• You are going to assess Binocular Single Vision
• You will be shown some lights
• You have to tell what how many lights you see
Inform the patient that :
6 m
33 cm
Near Distance
11. Worth 4 dot glass Principle
R
G G
W
Through Green lens
Through Red lens
W
W
Red filter blocks the
green light
Green filter blocks
the red light
12. Binocular Single Vision
Step by step procedure (Near)
Ask the patient to wear Read and green glasses
Hold the torch with red light at the top and white light at the bottom at 33cm
Ask the following questions
• How many lights are you seeing?
• What color are they?
• Where are they located?
• Are all the lights in line? Or are some higher than others?
• Do all the lights show up at a time/are they flashing on and off?
Document the findings
13. Binocular Single Vision
Step by step procedure (Distance)
Ask the patient to wear the glasses (Red and Green glasses)
Turn on the Worth 4-dot target for distance BSV ask the patient to
view the target at eye level to avoid parallax error
Ask the following questions:
• How many lights are you seeing?
• What color are they?
• Where are they located?
• Are all the lights in line? Or are some higher than others?
• Do all the lights show up at one time, or are they flashing on and off?
Document the findings
14. Points to remember
Perform the test with low illumination/light
Ask the patient to view the lights at eye level to avoid parallax
error
Do not switch on the target until the patient wears the glass
Wait for the patient to respond “how they see”
19. Learning Outcomes
Describe Binocular single Vision
Detail the procedure to assess Binocular Single Vision
Help the patient in responding
Interpret the patient’s responses
