Human Anatomy - Kotsan I. Ya. 2009

Sense Organs
Organ of Vision (Eye)
Age-Related Features of the Organ of Vision

The Eyeball of a newborn is relatively large, with an anteroposterior diameter of 17.5 mm and a weight of 2.3 g. The visual axis of the newborn's eyeball is positioned more laterally than in adults. The eyeball grows more rapidly During the first year of life than in subsequent years. By the age of 5, the weight of the eyeball increases by 70%, and by the age of 20–25, it increases threefold compared to that of a newborn.

The cornea in a newborn is relatively thick, and its curvature remains nearly unchanged throughout life.

The crystalline lens of a newborn is almost spherical, with the radii of its anterior and posterior curvature being approximately equal. The lens grows particularly fast during the first year of life, after which its growth rate declines.

The iris in a newborn is convex anteriorly, contains little pigment, and has a pupil diameter of 2.5 mm. As the child grows, the thickness of the iris increases, The amount of pigment in it rises, and the pupil diameter becomes larger. At the age of 40–50, the pupil narrows slightly.

The ciliary body in a newborn is poorly developed. The growth and Differentiation of the ciliary Muscle occur quite rapidly.

The Optic nerve in a newborn is thin (0.8 mm) and short. By the age of 20, its diameter nearly doubles.

The extraocular Muscles in a newborn are fairly well developed, with the exception of their tendinous portions. Consequently, Eye Movements are possible immediately after birth, but the coordination of these movements begins to develop from the second month of life.

The lacrimal gland in a newborn is small, and its excretory ducts are very thin. Lacrimation function appears in the infant during the second month of life.

The Sheath of the eyeball in newborns and infants is thin, and the adipose body of the Orbit is poorly developed. In elderly individuals, the orbital fat pad decreases in size and partially atrophies, causing the eyeball to recede deeper into the orbit.

The palpebral fissure in a newborn is narrow, and the medial angle of the eye is rounded. Subsequently, the palpebral fissure enlarges rapidly. In children up to 14 years of age, it is wide, making the eye appear larger than in an adult.