Fig. 2 Neuroanatomic integration of compositional and hydrodynamic factors. Two neuronal reflexes are involved to integrate both factors as an integral unit to maintain a stable tear film. Both reflexes are triggered by the sensory input of the first branch of the trigeminal nerve (V1), while the compositional one is mediated by the parasympathetic branch of the facial nerve (VII), and the hydrodynamic one is mediated by the motor branch of the facial nerve.