Abstract
Purpose: :
Subjects after cataract surgery lose completely their lens flexibility and thus their accommodation capability and need to function with a monofocal lens. The precision of the surgery determines the focal distance and amount of astigmatic aberrations. We present a design and simulations of a novel extended depth of focus (EDOF) technology incorporated into intra-ocular lenses' (IOL) that will allow the subject to have astigmatic and chromatic aberrations-free continuous focusing ability from 33cm to infinity.
Methods: :
The EDOF element was engraved on a surface of a monofocal rigid IOL as a series of shallow (less than one micron deep) concentric grooves around the optical axis. These grooves create an interference pattern extending the focus from a point to a length of about one mm providing a depth of focus of 3.00D with negligible loss of energy while significantly reducing the astigmatic aberration generated due to the tilting tolerances of the IOL during its implantation stage. The EDOF IOL was tested on an optical bench simulating the eye model.
Results: :
The performance of the proposed IOL was tested for pupil diameter of 2-6mm and for various spectral illuminations. The MTF charts demonstrate uniform performance of the lens for up to 3.00D at various illumination wavelengths and pupil diameters while preserving a continuous contrast of above 25% for spatial frequencies of up to 25 cycles/mm. Minimal sensitivity to decentration of up to 1mm and to tilting of up to 5 degrees was measured.
Conclusions: :
The proposed EDOF IOL technology was tested in numerical simulations as well as being experimentally characterized on an optical bench. The new lens is capable of solving the presbyopia and the astigmatism that accompany the implantation of conventional IOLs by providing focus extension of 3.00D under various illumination conditions, wavelengths, pupil diameters, decentrations and tilting of the lens.
Keywords: intraocular lens • cataract • depth