Growth of the Internal and External Eye in Term and Preterm Infants

Abstract

Better knowledge of the growth patterns of the external and internal eyes of neonates would permit more accurate diagnosis of disorders that affect ocular size such as infantile glaucoma and microphthalmos. Such disorders preferentially may affect certain parts of the internal eye but not other parts. No previous study statistically has evaluated internal ocular growth in preterm newborns. A-scan ultrasonography was applied directly to the corneas of 101 healthy preterm and term newborns to determine axial length, anterior chamber depth, lens thickness, and vitreous chamber depth. The growth of these structures was evaluated by correlation and regression analyses. At term, the mean measurements were axial length, 16.2 mm; anterior chamber depth, 2.0 mm; lens thickness, 3.8 mm; and vitreous chamber depth, 10.5 mm. Postconceptional age correlated to axial length (P < 0.001), anterior chamber depth (P = 0.032), and vitreous chamber depth (P < 0.001), but not to lens thickness (P = 0.48). By regression analysis, the eyes of males grew faster than those of females (P < 0.001) mainly due to the vitreous chamber. In the last trimester and first 2 postnatal months, lens thickness remains constant, while the anterior chamber and, especially, the vitreous chamber deepen.