The eyes and brain work together with amazing efficiency. Light rays enter the front of the eye and are interpreted by the brain as images. Light rays first enter your child’s eye through the cornea, the “window” of the eye. The cornea is a clear dome that helps the eyes focus.
The anterior chamber is located behind the cornea and in front of the iris. The anterior chamber is filled with a fluid that maintains eye pressure, nourishes the eye, and keeps it healthy. The iris is the colored part of your child’s eye. Eye color varies from person to person and includes shades of blue, green, brown, and hazel. The iris contains two sets of muscles. The muscles work to make the pupil of the eye larger or smaller. The pupil is the black circle in the center of the iris. It changes size to allow more or less light to enter your child’s eye.
After light comes through the pupil, it enters the lens. The lens is a clear curved disc. Muscles adjust the curve in the lens to focus clear images on the retina. The retina is located at the back of your child’s eye.
The inner eye, the space between the posterior chamber behind the lens and the retina, is called the vitreous body. It is filled with a clear gel substance that gives the eye its shape. Light rays pass through the gel on their way from the lens to the retina.
The retina is a thin tissue layer that contains millions of nerve cells. The nerve cells are sensitive to light. Cones and rods are specialized receptor cells. Cones are specialized for color vision and detailed vision, such as for reading or identifying distant objects. Cones work best with bright light. The greatest concentration of cones is found in the macula and fovea at the center of the retina. The macula is the center of visual attention. The fovea is the site of visual acuity or best visual sharpness. Rods are located throughout the rest of the retina.
The eyes contain more rods than cones. Rods work best in low light. Rods perceive blacks, whites, and grays, but not colors. They detect general shapes. Rods are used for night vision and peripheral vision. High concentrations of rods at the outer portions of the retina act as motion detectors in your child’s peripheral or side vision.
The receptor cells in the retina send nerve messages about what your child sees to the optic nerve. The optic nerves extend from the back of each eye and join together in the brain at the optic chiasm. From the optic chiasm, the nerve signals travel along two optic tracts, and eventually to the occipital cortex where vision is processed and perceived.