The Worth Four Dot Test: Is it Really “Worthless”?

The Worth 4 Dot Test was introduced by Claude Worth in 1903 as a test measuring binocularity. Hardy, in 1937, incorporated the lights of Worth into a hand-held flashlight. Further modifications were made by Behrens, Muenzler, and Raab. The W4D has become a standard test of sensory function in most strabismus practices. However, the targets have not been standardized in their manufacturing. Since the target size determines the visual angle the target subtends when the distance is held constant, the variability of target size leads to a lack of standardization of the test results.In our practice, the size of each W4D test used in our clinic has been measured and the visual angles calculated for distances from 13 inches to 20 feet, therefore, measuring the response elicited during the W4D test. This visual angle, denoting fusion, can be compared on subsequent examinations.The results of this testing procedure on 119 patients is reported. This procedure is a simple modification and we recommend its use whenever the W4D test is administered.