.png){kind=small}
Worth Four Dot Test
The Worth Four Dot Test is a clinical tool used to evaluate a patient's binocular vision, particularly the presence or absence of fusion, suppression, or diplopia. It is a subjective sensory test commonly performed in patients with strabismus or other binocular vision anomalies.
Principle of the Worth Four Dot Test
-
The patient wears red-green goggles:
-
Red filter over the right eye
-
Green filter over the left eye
-
-
The test target contains four dots arranged in a diamond shape:
-
1 Red dot (at the top)
-
2 Green dots (left and right)
-
1 White dot (at the bottom)
-
▶️ How the Filters Work:
-
The red filter allows only red light to pass and blocks green light.
-
The green filter allows only green light to pass and blocks red light.
-
The white dot contains both red and green light and can be seen by both eyes (fused image).
This dissociation allows the examiner to determine which eye is seeing which dot and whether the brain is fusing images or suppressing one eye.
👓 What Should a Normal Person See?
When a normal person (with no suppression or diplopia) wears the red-green goggles:
| Dot Color | Seen by | Description |
|---|---|---|
| 🔴 Red Dot (top) | Right eye (red filter) | Seen as red |
| 🟢 Green Dots (left and right) | Left eye (green filter) | Seen as green |
| ⚪ White Dot (bottom) | Both eyes (contains red + green light) | Yellowish or pinkish white (fused image) |
✅ Total Perception: 4 Dots
-
1 Red
-
2 Green
-
1 Mixed white/yellowish
This response indicates normal binocular single vision (BSV) with central fusion.
Clinical Uses of the Test
-
Detect suppression (if one eye is ignored by the brain)
-
Identify diplopia (if both eyes are active but not fusing)
-
Assess fusion ability (how well eyes combine visual input)
-
Monitor progress in strabismus or amblyopia management
Test Procedure
1. Preparation
-
Dim the room lights to enhance dot visibility.
-
Ask the patient to wear red-green goggles (Red on Right, Green on Left).
-
Use a Worth Four Dot Torch or a projected Worth Dot target (available at near [33 cm] or distance [6 m]).
2. Instructions to Patient
Ask the patient:
-
"How many dots do you see?"
-
"What colors do you see?"
-
"Where are the dots located?"
🔍 Interpretation of Results
| Patient’s Response | Interpretation |
|---|---|
| 4 dots (1 red, 2 green, 1 yellowish-white) | ✅ Normal fusion and binocular vision |
| 2 red dots only | Suppression of left eye (only right eye seeing) |
| 3 green dots only | Suppression of right eye (only left eye seeing) |
| 5 dots (2 red + 3 green) | Diplopia – both eyes active but not fusing |
| Dots appear moving or misaligned | May indicate anomalous retinal correspondence (ARC) or unstable fusion |
Additional Notes
-
The test is distance-dependent:
-
Near (33 cm): Tests central suppression
-
Distance (6 m): Tests peripheral suppression
-
-
It is useful before and after strabismus surgery, in amblyopia therapy, and in vision therapy programs.
-
The white dot appearing yellow or pink confirms both eyes are involved (fusion).
🧾 Advantages
-
Simple, quick, non-invasive
-
Can be used at near or far distance
-
Helps in differentiating suppression vs. diplopia
-
Important in treatment planning
⚠️ Limitations
-
Subjective – depends on patient’s response
-
Not ideal for old age or non-verbal children
-
Does not quantify the depth of suppression or size of deviation
Conclusion
The Worth Four Dot Test is a reliable and widely used test in Optometry and Ophthalmology for assessing sensory binocular vision. It works on the principle of color dissociation through red-green filters to test fusion, suppression, or diplopia. Understanding its interpretation is crucial for diagnosing and managing strabismus, amblyopia, and other binocular vision disorders.