The zones of discontinuity in the human lens: development and distribution with age

Statistical analysis of Scheimpflug images from the crystalline lenses of 100 emmetropic human subjects ranging in age from 18 to 70 yr confirms that specific zones of discontinuity are a function of lens development and growth. At and beyond the age of 40 yr, as many as four sharply demarcated and complementary zones are seen within the anterior and posterior lens cortex. The locations of the inner edges of the anterior cortical zones of discontinuity were characterized relative to the central sulcus of the lens. Consecutively from the central sulcus, the distances were 1.094, 1.415, 1.695, and 1.994 (+/- 0.11 mm). Since nuclear thickness in the adult lens is age-independent and the rate of cortical growth has been characterized, the location of the inner margins of the zones are indicative of the age at which they originated; these ages were 4 (+/- 1 yr), 9 (+/- 2 yr), 19 (+/- 4yr), and 46 (+/- 10 yr). All of the zones become broader along the outer margin and more dense upon aging, with specific zones appearing to merge in older presbyopic lenses. While lens fetal nuclear transparency decreases with age, it does not feature zones of discontinuity; instead, symmetrically amorphous regions appear centrally in the anterior and posterior nucleus. This demonstration of the onset of specific zones of discontinuity in emmetropic individuals, at defined periods of lens growth that are synchronous the production of successively more complex lens sutures, strongly suggests a causal relationship between lens sutures and the zones of discontinuity.