eyes

Eyes are sensory organs that detect light and enable vision in humans and many other animals. In humans, a pair of complex structures resides in the orbits of the skull. They convert light into neural signals, allowing perception of shapes, movement, color, and depth.

Anatomy includes external and internal components: eyelids and eyelashes protect the eye; the cornea and sclera form the outer coat; the conjunctiva covers the sclera. Inside are the uvea (iris, ciliary body, choroid), the lens, the vitreous humor, and the retina with photoreceptors (rods and cones). The optic nerve transmits signals to the brain, where the visual cortex interprets them.

Light enters through the cornea, passes through the pupil, and is focused by the lens onto the retina. Rods function in low light; cones enable color and detail. Signals travel to the brain via the optic nerve; information from each eye partly crosses at the optic chiasm, enabling binocular depth perception and a combined visual field.

Eyes develop from neural tissue early in embryogenesis. They are subject to refractive errors (myopia, hyperopia, astigmatism) and aging-related conditions such as cataracts and age-related macular degeneration. Regular eye exams aid in early detection of disease and vision problems. Trauma, infections, and systemic diseases can also impact eye health and function.