Chapter 1: Anatomy & Embryology of the Eye
III. GROWTH & DEVELOPMENT OF THE EYE
Eyeball
At birth, the eye is larger in relation to the rest of the body than is the case in children and adults. In relation to its ultimate size (reached at 7-8 years), it is comparatively short, averaging 16.5 mm in anteroposterior diameter (the only optically significant dimension). This would make the eye quite hyperopic if it were not for the refractive power of the nearly spherical lens.
Cornea
The newborn infant has a relatively large cornea that reaches adult size by the age of 2 years. It is flatter than the adult cornea, and its curvature is greater at the periphery than in the center. (The reverse is true in adults.)
Lens
At birth, the lens is more nearly spherical in shape than later in life, producing a greater refractive power that helps to compensate for the short anteroposterior diameter of the eye. The lens grows throughout life as new fibers are added to the periphery, making it flatter.
The consistency of the lens material changes throughout life. At birth, it may be compared with soft plastic; in old age, the lens is of a glass-like consistency. This accounts for the greater resistance to change of shape in accommodation as one grows older.
Iris
At birth, there is little or no pigment on the anterior surface of the iris; the posterior pigment layer showing through the translucent tissue gives the eyes of most infants a bluish color. As the pigment begins to appear on the anterior surface, the iris assumes its definitive color. If considerable pigment is deposited, the eyes become brown. Less iris stroma pigmentation results in blue, hazel, or green coloration.
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10.1036/1535-8860.ch1