Abstract
The lens of the eye has a gradient refractive index (GRIN). Ocular accommodation, which alters the shape of the lens in response to visual demand, causes a redistribution of the internal structure of the lens leading to a change in the GRIN profile. The nature of this redistribution and the consequence of change in the GRIN profile are not understood. A modelling approach that considers how the GRIN profile may change with accommodation needs to take into account optical and mechanical parameters and be cognisant of individual variability in the shape and size of lenses. This study models the normalised axial GRIN profile during accommodation using reduced modelling and incorporating finite element analysis to connect inhomogenous mechanical characteristics of the lens to optical performance. The results show that simulated stretching changes the length of the plateau but does not alter the cortical gradient, which supports clinical findings. There is a very small change to the accommodated and non-accommodated profiles when normalised, yet this yields measurable changes in aberrations with around 11% and almost 13% difference in spherical aberration and astigmatism respectively. The results can be used in reconstruction of the refractive index and for investigating gradual changes with age.
Highlights
The lens of the eye is a gradient refractive index (GRIN) structure, a characteristic that attenuates the monochromatic and chromatic aberrations [1,2,3,4,5,6,7]
As the thickness of the lens alters with accommodation, there is a change in the axial GRIN profile
Whilst the GRIN nature of the lens has been investigated in many studies [22], there is comparatively less work on the mechanics of the lens and on the opto-mechanical changes with accommodation
Summary
The lens of the eye is a gradient refractive index (GRIN) structure, a characteristic that attenuates the monochromatic and chromatic aberrations [1,2,3,4,5,6,7]. The aspect of the GRIN structure that is most pertinent to vision is the axial GRIN profile which plays an important role in optical power of the eye and has an effect on the third-order aberrations [6] The steepness of this profile has been suggested as a measure of age-related change [20,24,25,26]. An axial reduced model of accommodation has been derived to examine GRIN profile adjustments This incorporates analysis from a finite element model that uses a distribution of modulus of elasticity based on the optical structure introduced by Bahrami and Goncharov [6]. The normalised axial profile of the lens can be used in comparative analyses of mechanical properties of the lens and in advanced modelling of accommodative behaviour
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
