Shape and GRIN contribute to age-related SA

Lens geometry and gradient refractive index (GRIN) can be reconstructed in isolated human lenses by using 3D optical coherence tomography and laser ray tracing, and both geometrical changes and the increase in the meridional power of GRIN play a role in lens spherical aberration (SA) caused by age, according to researchers in Madrid.

The researchers used 3D-sOCT to image 35 human donor lenses from people aged 19 to 71 years. Laser ray tracing was used to measure paraxial and non-paraxial back focal length. By using a global search algorithm, the researchers were able to reconstruct the parameters of a four-variable, 3D GRIN model. SA was then calculated for the GRIN lenses, as well as their corresponding homogeneous lenses.

It was found that age causes significant increases in both lens thickness and radii of curvature. While posterior values remained nearly constant (slope: 0.0275, P = 0.002), the negative anterior conic constant shifted positive (slope: 0.228, P

A flattening of GRIN distribution was indicated by the tendency of the GRIN meridional power exponent to increase, while the axial exponent remained nearly constant.

The equivalent index did not display significant age-dependence. The back focal length significantly increased with age (P P P

The research was published in Investigative Ophthalmology and Visual Science. To view the abstract, click here.