The eye is a unique organ that is virtually impermeable to
most environmental agents. Continuous tear flow, aided
by the blink reflex, mechanically washes substances from
the ocular surface and prevents the accumulation of
microorganisms. In addition, lysozyme, lactoferrin,
secretory immunoglobulins, and defensins are present at
high levels in tears and can specifically reduce bacterial
colonization of the ocular surface [ 7