Final answer:
The transparent tissue on the outer surface of the eyeball is the cornea, which allows light to enter the eye and is essential for vision.
Step-by-step explanation:
The transparent tissue that forms the outer surface of the eyeball is known as the cornea. The cornea is part of the fibrous tunic, which is the outermost layer of the eye. This layer also includes the sclera, or the white of the eye. While the sclera accounts for the majority of the eyeball's surface, the clear cornea covers the anterior tip of the eye and plays a crucial role in vision by allowing light to enter. The cornea, along with the lens, acts to form a focused image on the retina, which is particularly concentrated at the fovea for high visual acuity.
The eye is a complex organ with other significant structures such as the vascular tunic which comprises the choroid, ciliary body, and iris, and the innermost neural tunic, or retina, responsible for photoreception. The cornea's importance in vision is underscored by its transparency and refractive properties, which are essential for light transduction.