Worth 4 Dot

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Article initiated by:

Amra Nadarević Vodenčarević, MD

All contributors:

Amra Nadarević Vodenčarević, MD, Jill Rotruck, MD, S. Grace Prakalapakorn, MD, MPH, Dr. Priyanka Kumar, MD

Assigned editor:

Jill Rotruck, MD

Review:

Assigned status Update Pending

 by Jill Rotruck, MD on April 16, 2025.

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Introduction

The Worth Four Light Test (Worth's Four Dot test, W4LT) is a clinical assessment used to evaluate binocular vision, including detection of diplopia, suppression, and anomalous retinal correspondence (ARC). It is simple, quick to perform, and can be used in verbal children.

Equipment

Red-green glasses and a Worth Four Dot flashlight or wall-mounted display

Procedure

With the red-green glasses on (red over the right eye) over top of any habitually worn refractive correction, the patient is shown a target with four illuminated dots in a diamond configuration: Red at 12 o'clock, Green at 3 and 9 o'clock, and White at 6 o'clock.

The test is performed at both 33 cm (near) and 6 m (distance). Room lights can be kept on to promote fusion or turned off to increase dissociation.

The patient is then asked to describe what they see, including the number, location, and color of lights. Patients should be asked if all of the lights are constant or if some come and go.

Interpretation

The red lens blocks green light, and the green lens blocks red light. The right eye sees red and the white dot (appearing red), while the left eye sees green and the white dot (appearing green). Fusion of the white light may appear as a mix of red/green or switch depending on ocular dominance.

Reported patient perception:

Worth 4 Dot test outcomes. A. Normal result. A normal results indicates anomalous retinal correspondece in patients with manifest strabismus at the time of testing B. Left eye suppression C. Right eye suppression D. Uncrossed diplopia E. Crossed diplopia

Four dots: This indicates a normal result in patients with normal alignment during testing. In patients with manifest strabismus during testing, this indicates anomalous retinal correspondence (ARC).

Two red dots: Left eye suppression

Three green dots: Right eye suppression

Five dots with red on the right and green on the left: Uncrossed diplopia. This is expected in esotropia and indicates ARC in exotropic patients.

Five dots with green on the right and red on the left: Crossed diplopia. This is expected in exotropia and indicates ARC in esotropic patients.

Suppression of one eye at distance with normal response at near: Consistent with a monofixation syndrome. A 1-4° degree scotoma is typical of monofixation syndrome. At ≥3 m, the flashlight projects ≤1° onto the central retina and will not be seen in the eye with the scotoma. At near, the lights project outside of the scotoma, allowing for the lights to be viewed with both eyes.  

References

1. Worth C. Squint: Its causes, pathology and treatment. Philadelphia: Blakiston, 1908
2. Noorden GK von. Binocular vision and ocular motility: theory and managment of strabismus, 5th Ed. St Louis: Mosby, 1996.
3. Duane’s Clinical Ophthalmology. New York: Lippincott Williams & Wilkins, 2005.
4. Jeon, HS., Choi, HY. (2019). Binocular Function Test. In: Lee, JS. (eds) Primary Eye Examination. Springer, Singapore. https://doi.org/10.1007/978-981-10-6940-6_6