The first line of defense in the protective system of the eye is formed by which of the following?

The first line of defense in the protective system of the eye is formed by the eyelids. Eyelids serve several important functions that protect the eye from environmental hazards. They physically shield the eye from dust, debris, and excessive light, helping to prevent injury and irritation. Additionally, eyelids aid in the distribution of tears across the surface of the eye, which is essential for maintaining ocular health and comfort. The blink reflex, triggered by stimuli, helps to remove irritants and keep the eye moist.

While the conjunctiva, cornea, and sclera play roles in protecting and maintaining the integrity of the eye, the eyelids are the most immediate barrier against external threats. The conjunctiva helps to protect the surface of the eye and maintain lubrication, the cornea acts as a transparent barrier that refracts light, and the sclera provides structural support. However, it is the eyelids that provide the first mechanical defense, reflecting their primary role in eye protection.