Growth and Development

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Chapter 610 Growth and Development

Scott E. Olitsky, Denise Hug, Laura S. Plummer, Merrill Stass-Isern

The eye of a normal full-term infant at birth is approximately 65% of adult size. Postnatal growth is maximal during the 1st yr, proceeds at a rapid but decelerating rate until the 3rd yr, and continues at a slower rate thereafter until puberty, after which little change occurs. The anterior structures of the eye are relatively large at birth but thereafter grow proportionately less than the posterior structures. This results in a progressive change in the shape of the globe; it becomes more spherical.

In an infant, the sclera is thin and translucent, with a bluish tinge. The cornea is relatively large in newborns (averaging 10 mm) and attains adult size (nearly 12 mm) by the age of 2 yr or earlier. Its curvature tends to flatten with age, with progressive change in the refractive properties of the eye. A normal cornea is perfectly clear. In infants born prematurely, the cornea may have a transient opalescent haze. The anterior chamber in a newborn appears shallow, and the angle structures, important in the maintenance of normal intraocular pressure, must undergo further differentiation after birth. The iris, typically light blue or gray at birth in white children, undergoes progressive change of color as the pigmentation of the stroma increases in the first 6 months of life. The pupils of a newborn infant tend to be small and are often difficult to dilate. Remnants of the pupillary membrane (anterior vascular capsule) are often evident on ophthalmoscopic examination, appearing as cobweb-like lines crossing the pupillary aperture, especially in preterm infants.

The lens of a newborn infant is more spherical than that of an adult; its greater refractive power helps to compensate for the relative shortness of the young eye. The lens continues to grow throughout life; new fibers added to the periphery continually push older fibers toward the center of the lens. With age, the lens becomes progressively denser and more resistant to change of shape during accommodation.

The fundus of a newborn’s eye is less pigmented than that of an adult; the choroidal vascular pattern is highly visible, and the retinal pigmentary pattern often has a fine peppery or mottled appearance. In some darkly pigmented infants, the fundus has a gray or opalescent sheen. In a newborn, the macular landmarks, particularly the foveal light reflex, are less well defined and might not be readily apparent. The peripheral retina appears pale or grayish, and the peripheral retinal vasculature is immature, especially in premature infants. The optic nerve head color varies from pink to slightly pale, sometimes grayish. Within 4-6 mo, the appearance of the fundus approximates that of the mature eye.

Superficial retinal hemorrhages may be observed in many newborn infants. These are usually absorbed promptly and rarely leave any permanent effect. The majority of birth-related retinal hemorrhages resolve within 2 wk, with complete resolution of all such hemorrhages within 4-6 wk of birth. Conjunctival hemorrhages also can occur at birth and are resorbed spontaneously without consequence.

Remnants of the primitive hyaloid vascular system may also be seen as small tufts or wormlike structures projecting from the disc (Bergmeister papilla) or as a fine strand traversing the vitreous; in some cases, only a small dot (Mittendorf dot) remains on the posterior aspect of the lens capsule.

An infant’s eye is somewhat hyperopic (farsighted). The general trend is for hyperopia to increase from birth until 7 yr of age. Thereafter, the level of hyperopia tends to decrease rapidly until age 14 yr. Elimination of the hyperopic state can occur during this time. If the process continues, myopia (nearsightedness) develops. A slower continuation of the decrease in hyperopia, or increase in myopia, continues into the 3rd decade of life. The refractive state at any time in life depends on the net effect of many factors: the size of the eye, the state of the lens, and the curvature of the cornea.

Newborn infants tend to keep their eyes closed much of the time, but normal newborns can see, respond to changes in illumination, and fixate points of contrast. The visual acuity in newborns is estimated to be approximately 20/400. One of the earliest responses to a formed visual stimulus is an infant’s regard for the mother’s face, evident especially during feeding. By 2 wk of age, an infant shows more-sustained interest in large objects, and by 8-10 wk of age, a normal infant can follow an object through an arc of 180 degrees. The acuity improves rapidly and can reach 20/30-20/20 by the age of 2-3 yr.

Many normal infants have imperfect coordination of the eye movements and alignment during the early days and weeks, but proper coordination should be achieved by 3-6 mo of age, usually sooner. Persistent deviation of an eye in an infant requires evaluation.

Tears often are not present with crying until after 1-3 mo of age. Preterm infants have reduced reflex and basal tear secretion, which can allow topically applied medications to become concentrated and lead to rapid drying of their corneas.

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