To assess the change of deviation angle after the patch test and +3.00 diopter (D) spherical lens test in basic intermittent exotropia.

The present study included 57 patients diagnosed with basic intermittent exotropia. The deviation angles at near and far before and after monocular occlusion of 40 minutes or more were measured. Afterward, change of deviation was also measured by placing +3.00 D spherical lenses at near.

Results from the study revealed pre-occlusion mean deviation angles of 23.1 ± 7.41 prism diopters (PD) at near, and 23.9 ± 6.56 PD at far. After the patch test, the mean deviation angles were increased to 28.3 ± 6.50 PD ( p < 0.0001) at near, and 25.5 ± 6.40 PD ( p < 0.0001) at far. After the +3.00 D spherical lens test, the angle was increased to 31.5 ± 7.53 PD ( p < 0.0001) at near. Using the gradient method, the average accommodation convergence - accommodation ratio was 1.4 ± 1.19 PD/D.

Both the patch test and +3.00 D spherical lens test significantly increased the deviation angles at near and far, they helped to find the maximum deviation angle in patients with basic intermittent exotropia.