Assessment of imaging with extended depth-of-field by means of the light sword lens in terms of visual acuity scale

Abstract

We present outcomes of an imaging experiment using the refractive light sword lens (LSL) as a contact lens in an optical system that serves as a simplified model of the presbyopic eye. The results show that the LSL produces significant improvements in visual acuity of the simplified presbyopic eye model over a wide range of defocus. Therefore, this element can be an interesting alternative for the multifocal contact and intraocular lenses currently used in ophthalmology. The second part of the article discusses possible modifications of the LSL profile in order to render it more suitable for fabrication and ophthalmological applications.

Keywords: (170.4470) Ophthalmology; (330.1070) Vision - acuity; (330.4460) Ophthalmic optics and devices; (330.7323) Visual optics, aging changes.

Figures

Fig. 1

Shape of the light sword lens (LSL) element.

Fig. 2

Samples of polymethylmethacrylate light sword lenses (LSLs) fabricated by injection technology.

Fig. 3

Profile of the light sword lens (LSL) sample used, measured by the profilometer Veeco Wyko NT9300 with a linear color scale (blue = 0 μm; red = 50 μm).

Fig. 4

The numerical interferogram of the ideal light sword lens (LSL) (left) and the interferogram of the LSL sample used, obtained with a Mach-Zehnder interferometer using monochromatic light with λ = 632.8 nm.

Fig. 5

Optical arrangement for imaging using the simplified presbyopic eye and the light sword lens (LSL) element.

Fig. 6

Relative comparison of ETDRS charts imaged experimentally by the simplified presbyopic eye (iris diameter: 3 mm) without (left column) and with (middle column) the light sword lens (LSL). See Media 1 for high resolution.

Fig. 7

High-resolution movie ( Media 2) of relative comparison of the simulated ETDRS chart images formed by the simplified presbyopic eye alone (left image) and with the light sword lens (LSL) added (right image). Counters of the defocus values and related object distances rescaled to the Gullstrand eye are given in the center of the image.

Fig. 8

Assessment of visual acuity (VA) of the simplified presbyopic eye for different values of defocus, rescaled to the Gullstrand eye. Red marks correspond to tests without the light sword lens (LSL). Black marks correspond to tests with the LSL. The blue line corresponds to the real normal eye with 3 mm diameter pupil (based on [29]).

Fig. 9

The light sword lens (LSL) with phase discontinuity (Θ = 0), and modified LSLs without phase discontinuity. Angular sectors of oppositely growing dioptric power with widths Θ = π/4 and π/2, respectively, were implemented in the second and third cases. Elements are presented in the form of a kinoform [30].

Fig. 10

Simulated output images formed by the light sword lens (LSL), as well as the modified LSL with discontinuities removed.