Final answer:
The cornea is the transparent front covering of the eye, which together with the lens, helps to focus light on the retina. It is part of the fibrous tunic that includes the sclera, and the size of the pupil is regulated by the iris to control light entry into the eye.
Step-by-step explanation:
The transparent covering over the eye is known as the cornea. It serves as a barrier protecting the inner eye from the outside world and plays a crucial role in focusing light waves as they enter the eye. The cornea is part of the eye's fibrous tunic, which also includes the white sclera, accounting for five-sixths of the eye's surface. This clear front layer, along with the lens, works in tandem to bend light and form an image on the retina. The sclera is the protective outer layer that is more visible in humans than in many other species, often referred to as the "white of the eye." The vitreous humor is a clear gel that fills the space behind the lens and is crucial for maintaining the eye's shape. Light entering the eye is modulated by the iris, the colored part of the eye, which adjusts its size to control the amount of light that reaches the retina through the pupil. All these components function together to enable vision.