While fMRI has identified which regions of interests (ROI) are functionally active during a vergence task (the inward or outward rotation of eyes), the functional connectivity between ROIs is less understood. This study tested the following hypotheses: 1) significant functional connectivity would be observed between the frontal eye fields (FEF), the posterior parietal cortex (PPC) and the cerebellar vermis (CV), 2) significantly more functional activity and connectivity would be observed in binocularly normal controls (BNC) compared to patients with convergence insufficiency (CI), and 3) after vergence training, the functional activity and connectivity would improve in CI subjects compared to their baseline measurements. A block design of sustained fixation versus vergence eye movements stimulated activity in the FEF, PPC and CV. FMRI data from four CI subjects before and after vergence training were compared to seven BNC. Functional activity was assessed using the BOLD percent signal change. Functional connectivity was assessed using a seed-based functional connectivity analysis, which revealed significant correlation between the FEF, PPC and CV ROIs.