The Usefulness of the Worth 4-Dot Test under Room Light On and Off in Intermittent Exotropes

ABSTRACT

PURPOSE: It is known that fusion is promoted in the presence of a peripheral fusion clue in patients with intermittent exotropia, X(T). Therefore, this study compared the results of the Worth 4-dot test (W4D) with the room lights on and off in order to determine the status of the binocular function. METHODS: The W4D test was performed with lights on and off, and the polarized 4-dot test (P4D) was administered in 52 X(T) patients. RESULTS: Among these 3 tests, the fusion rate was the lowest with distance in the W4D with the lights off at 9.6%, which was followed by the W4D with the lights on at 26.9% and the P4D at 57.7%. The fusion rate of the W4D with the lights on in the patients with a distance stereoacuity better than 120 seconds of arc (") was 50%, which was significantly higher than the 18.4% observed in the patients with a stereoacuity at 120" or worse (P=0.023). Among the 14 patients who showed fusion with the distance W4D with the lights on, 10 could not fused with the W4D with the lights off. Therefore, a weak motor fusion was observed in 71.4 % of these 14 patients. CONCLUSIONS: It is possible to verify the more natural condition of the binocular sensory function of patients with X(T) using either the P4D or the W4D with the lights on rather than with the lights off. Furthermore, the W4D test with the lights on can be performed together with and be compared with that conducted with the lights off, for a better understand of the degree of motor fusion.