axial length of the eye

length of the eye, axial

The distance between the anterior and posterior poles of the eye. In vivo, it is measured either by ultrasonography or by partial coherence interferometry (PCI). These measurements represent the distance between the anterior pole and Bruch's membrane. (In young eyes in which there is a refractive index difference at the retina-vitreous interface ultrasonography measures the distance between the anterior pole and the anterior surface of the retina.) The axial length of the eye at birth is approximately 17 mm and reaches approximately 24 mm in adulthood. It is typically longer than 24 mm in myopes and shorter than 24 mm in hyperopes. Each mm of change in axial length of the eye corresponds to approximately 2.5 D See biometry of the eye; ultrasonography.