Purpose: "Touching four" dots on the Worth 4-dot test is used sometimes as an indication of fusion in young children. The authors examined the reliability of this test.
Methods: A computer simulation of the Worth 4-dot test generated images representing fusion, suppression, and alternate fixation. Sixteen children, ranging in age from 32 to 48 months, were examined using this test.
Results: None of the children could accurately describe the images verbally. Alternate fixation could not be distinguished from fusion by asking the subjects to touch the dots. Monocular suppression was identified accurately in all subjects.
Conclusion: Touching four dots on the Worth 4-dot test does not distinguish fusion from alternate fixation in children with normal ocular alignment. This has important implications regarding the diagnosis of monofixation syndrome and assessment of the response to a prism adaptation trial in young children.