Worth Four dot Test (Worth 4 dot Test)

 

 Introduction

The Worth four-dot test was first described 100 years ago.

The Worth four-dot test consists of four lights arranged in a diamond shape, with a red light at the top, two green lights on the left and right sides, and a white light at the bottom.

Worth 4 dot Test

Worth four-dot test is a gross test that assesses suppression by asking the patient to report the number and color of the dots they can see when looking through red-green glasses at four different lights or dots.

The transmission characteristics of red-green glasses (Armstrong glasses) are such that the eye using the red filter (usually the right eye) blocks the green light to see only the top and bottom lights, and the eye seeing through the green filter (usually the left eye) blocks the red light and can see the two green lights and the bottom light.

The bottom light is seen by both eyes. A patient with normal binocular vision will appreciate four lights with a red-green light flashing at the bottom due to binocular rivalry.

Therefore, when a patient sees all four dots, it is suspected that they have a normal binocular fusion response without manifest strabismus or anomalous retinal correspondence.

Methods of Performing the Four-Dot Test

Two Methods of Performing the Four-Dot Test

• Distance Worth four-dot test: The target is fixed at a distance of 6 meters from the patient, which can be projected onto an illuminated box or screen.
• Near Worth four-dot test: The target is fixed at a distance of 33 cm from the patient, consisting of a flashlight that helps alter the projection angle.
  
  
  

Requirements To Perform Worth Four Dot Test

test frame, red-green filter, red-green filter glasses, four-dot display - Worth four-dot test value

Requirements for Performing the Four-Dot Test

Test frame with red and green filter or red and green filter glasses (Armstrong Goggle).

Illuminated four-dot box or flashlight.

Suppression Assessment

Normal motor system function is essential for binocular vision but does not guarantee the existence of binocular vision.

Suppression tests determine whether the patient has the ability to combine the images from the left and right eyes.

If the retinal images differ in size due to aniseikonia or in clarity such as in amblyopia, uncorrected anisometropia, or unilateral eye diseases, it may be that the images from the two eyes are not fused because one eye is suppressed.

An inability to appreciate diplopia in some motor system evaluations, such as near point of convergence, may have already suggested suppression.

Simple suppression assessments are also available in the Mallett unit and with some stereopsis tests.

Binocular refraction techniques, such as Turville's infinite balance, can also assess gross suppression.

Indication of the Value of the Four-Dot Test

Manifest strabismus: Helps identify manifest vertical and horizontal strabismus.

• Esotropia
• Exotropia
• Hypertropia
• Hypotropia

Diplopia: This test can help determine the nature and type of diplopia.

• Crossed diplopia
• Non-crossed diplopia

Suppression: Helps identify which eye is suppressed.

Procedure

Explain the test and procedure to the patient: "This test checks if you are using both eyes at the same time for viewing."

The patient should wear red-green glasses (Armstrong glasses). The eye with the red filter in front (usually the left eye) will see the red light, and the eye with the green filter in front (usually the right eye) will be able to see the green light. Make sure the patient cannot see the flashlight before putting on the red and green glasses.

For testing at 6 meters: Ensure the patient is wearing prescribed glasses or contact lenses.

For testing at 33 meters.

There are four possible responses:

If the patient sees all four points: Two possibilities

• Normal retinal correspondence without manifest strabismus (patient will be orthophoric or absence of tropia)
• Abnormal retinal correspondence with manifest strabismus (presence of tropia)

If the patient sees 3 points: Suppression of the right eye

If the patient sees 2 points: Suppression of the left eye

If the patient sees 5 points: Diplopia

• Non-crossed diplopia: If the patient sees green dots on the left side of the red dots, it indicates non-crossed diplopia. This response is given by a patient with esotropia.
• Crossed diplopia: If the patient sees green dots on the right side of the red dots, it indicates crossed diplopia. This response is given by a patient with exotropia.

• If the patient sees green dots above the red dots, it indicates right hypertropia or left hypotropia.
• If the patient sees red dots above the green dots, it indicates right hypotropia or left hypertropia.
• If the patient can report 4 points at 33 cm but is unable to report all four (two red or three green) at 1m, it indicates the presence of a small suppression scotoma. If the patient is unable to report all four points at 33 cm, it indicates a large suppression scotoma.