Abstract
Purpose:
Accommodation of the human eye involves a loop of biological and optical processes, including the ciliary muscle contraction, the lens shape deformation, and the change of ocular wavefront aberrations. But, inter-relationship of the accommodative changes between different accommodative components within the loop has not been well explored. The purpose of this study was to study the inter-relationship between the different components by in vivo measuring accommodative changes of the wavefront aberration, lens shape and ciliary muscle for emmetropic young adults.
Methods:
A Hartmann-Shack wavefront sensor, integrated with two OCT systems, was developed to measure wavefront aberrations for 15 subjects (aged 22 to 27 yrs old; Rx from -0.50 to +1.00D) during accommodation. One OCT system was used to image the lens deformation while the other was aligned for imaging ciliary muscle contraction.
Results:
Over a 6D accommodation, mean accommodative changes were: 5.43±0.26D in refractive power; -0.083±0.027 micron in spherical aberration, 44.4±7.5 and 24.0.1±21.3 (m-1) in curvature of the anterior and posterior lens surfaces respectively, 0.38±0.03mm in lens thickness (LT), and 0.065±0.048mm in the difference of ciliary thickness between 1.0mm and 3.0mm from the scleral spur. For individual eye, the change in anterior lens curvature was significantly correlated to the refractive power change (mean correlation coefficient r=0.97) and also to the change in the difference of ciliary thickness (mean r=0.81). The LT was negatively correlated to spherical aberration for every eye (mean r=-0.95).
Conclusions:
For emmetropic eye, accommodative change in refractive power is in proportion to the changes in lens curvatures, which are in turn proportionally related to the change of ciliary muscle thickness. The results provide basic information for characterizing accommodation performance and also for designing accommodative intraocular lens.