Magnetic resonance imaging study of the effects of age and accommodation on the human lens cross-sectional area.

PURPOSE To evaluate the effect of age and accommodation on lens cross-sectional area (CSA). METHODS High-resolution magnetic resonance images of the eye were acquired from 25 subjects ranging in age from 22 to 50 years during accommodation and with accommodation at rest. The images were analyzed to obtain the total lens CSA and the CSAs of the anterior and posterior portions of the lens. RESULTS The total lens CSA and the CSA of the anterior portion increased with age in both accommodative states. With accommodation, the CSA was larger in these portions of the lens; however, this difference decreased with age. Conversely, the CSA of the posterior portion of the lens remained statistically independent of both age and accommodative state. CONCLUSIONS This preliminary study documents, in vivo, that the lens grows with age. This growth appears to be confined to the anterior portion. A quite unexpected finding is that both the total lens CSA and the CSA of the anterior portion are greater during accommodation when zonular tension is minimized. This accommodative change in CSA, which decreases with age, may be due to compression of the lens material during relaxed accommodation when zonular tension is greatest. That both age and accommodative changes in CSA appear to be limited to the anterior portion of the lens may be related to properties of the anterior capsule and lens material, the position of the zonular attachments, and the location of the fetal nucleus.