IL6 and dry eye syndrome: Both IL-1β and IL-6 are proinflammatory cytokines that are secreted on the ocular surface in response to various pathologic stimuli, such as benzalkonium chloride-induced dry eye, desiccating stress induced dry eye, and microbial infections, such as P. aeruginosa, O. volvulus, or HSV-1 [20,38–40].