Age related changes of the crystalline lens

Abstract

SummaryThe crystalline lens has a double function to aid the cornea in focusing light rays on the retina and to accommodate to focus near objects. The refractive power of the lens is about half of that of the cornea, but a young lens can increase its power by more than 50%. Its gradient refractive index (GRIN) provides additional refractive power and amplitude of accommodation (AA). The optical properties of the lens change dramatically with age. The lens continues to grow throughout life (lens thickness increases about 0.024 mm/year) which has a strong impact on its optical properties. With ageing most of the GRIN tends to concentrate near the surface, which causes a decrease of both power and AA. The lens also gets stiffer with age. The maximum AA is reached early (ages 8‐12 years) and then declines at a mean rate of 0.25 D/year; accommodation becomes residual after 50 years. The optical quality of the lens suffers a strong age‐related deterioration: progressive lens yellowing tends to filter short wavelengths, stray light increases with age, which strongly increases the probability of cataracts. Spherical and other higher order aberrations of the lens increase so that they can duplicate their RMS value from 35 years to 75 years.