Presbyopia is an ophthalmic condition wherein the eye loses the ability to focus clearly due to lens aging. It can significantly affect the quality of life. Since eventually, every person will inevitably develop this condition, it is important to find a solution to it.
Currently, spectacle-free treatment can be achieved by using contact lenses and intraocular lenses. However, existing solutions of monofocal, bifocal and trifocal lens designs leave a lot to be desired.
A monofocal EDoF lens can hardly reach 2D of depth of focus (DoF). Bifocal lenses suffer from degraded intermediate distance image quality and pupil-size dependency. Trifocal diffractive lenses provide improved intermediate image quality, but with degraded image quality between the focal points.
This invention is a new approach to designing refractive, presbyopia-correcting ophthalmic lenses with a large continuous DoF, independent of pupil size. A design example was found and used to evaluate the performance through focus. The area MTF was well balanced through 2.5D of DoF for a range of pupil sizes (from 3mm to 5mm). The orientation of the 20/20 letter ‘E’ on a visual acuity chart was clearly recognized subjectively over defocus ranging from 0 to 2.5D.