Alex Zlotnik

Extended depth of focus contact lenses for presbyopia

The purpose of this Letter is to design, develop, fabricate, and test in clinical trials a new (to our knowledge) type of contact lenses that provides simultaneous near and distance focused vision for presbyopic subjects, including those with up to 2.00 diopters (D) of regular/irregular astigmatism, as an alternative to multifocal contact lenses. The purpose is obtained by generating an optical pattern on the front surface of contact lenses, capable of extending the depth of focus of lenses by 3.00 D with high visual contrast. The pattern was fabricated on top of contact lenses and tested by the use of an eye simulation as well as in clinical trials. Use of the extended depth of focus contact lens enabled patients to achieve good visual acuity and contrast sensitivity for both distance and near vision without compromising the energy distribution or the visual fields.

Extending the depth of focus for enhanced three-dimensional imaging and profilometry: an overview

We overview the benefits that extended depth of focus technology may provide for three-dimensional imaging and profilometry. The approaches for which the extended depth of focus benefits are being examined include stereoscopy, light coherence, pattern projection, scanning line, speckles projection, and projection of axially varied shapes.

Intraocular omni-focal lens with increased tolerance to decentration and astigmatism.

PURPOSE To measure the optical performance of an extended depth of focus (EDOF) intraocular lens (IOL), which provides an imaging solution for near, intermediate, and distance ranges, and to compare its optical performance to available bifocal IOLs with various extents of decentration and astigmatism aberrations. METHODS A special profile that performs interference principle-based focal extension is engraved on the top of a monofocal rigid IOL. An optical bench based on the L&B eye model was used to test the performance in comparison with the bifocal AcrySof ReSTOR SA60D3 lens (Alcon Laboratories Inc). RESULTS The imaging performances at near, intermediate, and distance ranges were mapped. Different decentration parameters and amount of astigmatism aberration were tested. In numerical simulations and the experimental bench, the EDOF IOL was demonstrated to have good visual acuity in near, intermediate, and distance ranges as well as reduced sensitivity to decentration of up to 0.75 mm and the capability of correcting astigmatism aberrations of up to 1.00 diopter. CONCLUSIONS Extended depth of focus technology is capable of providing clear and focused vision at near, intermediate, and distance ranges. Its high quality imaging is obtained under large decentration conditions and residual astigmatism. This capability broadens the potential use of the technology beyond its application as a simultaneous multifocal lens.

Omni-focal refractive focus correction technology as a substitute for bi/multi-focal intraocular lenses, contact lenses, and spectacles

We present novel technology for extension in depth of focus of imaging lenses for use in ophthalmic lenses correcting myopia, hyperopia with regular/irregular astigmatism and presbyopia. This technology produces continuous focus without appreciable loss of energy. It is incorporated as a coating or engraving on the surface for spectacles, contact or intraocular lenses. It was fabricated and tested in simulations and in clinical trials. From the various testing this technology seems to provide a satisfactory single-lens solution. Obtained performance is apparently better than those of existing multi/bifocal lenses and it is modular enough to provide solution to various ophthalmic applications.

Axially and transversally super-resolved imaging and ranging with random aperture coding

In this paper we present a new approach allowing improved imaging capabilities while using imaging lenses with higher tolerances to fabrication errors. The idea is to attach a random phase to the aperture plane of the imaging lens, which generates a random phase in the optical transfer function distribution. This phase is a priori known and it is very much dependent on the range to the object. The randomness of this phase allows simultaneously increasing the depth of focus as well as estimating the range to the various objects in the field of view of the imager. In addition it allows increasing the geometrical resolution of the imager by orthogonal coding of the spatial spectral bands prior to their folding due to the under-sampling by the detector (aliased information).

Head mounted DMD based projection system for natural and prosthetic visual stimulation in freely moving rats

Novel technologies are constantly under development for vision restoration in blind patients. Many of these emerging technologies are based on the projection of high intensity light patterns at specific wavelengths, raising the need for the development of specialized projection systems. Here we present and characterize a novel projection system that meets the requirements for artificial retinal stimulation in rats and enables the recording of cortical responses. The system is based on a customized miniature Digital Mirror Device (DMD) for pattern projection, in both visible (525 nm) and NIR (915 nm) wavelengths, and a lens periscope for relaying the pattern directly onto the animal’s retina. Thorough system characterization and the investigation of the effect of various parameters on obtained image quality were performed using ZEMAX. Simulation results revealed that images with an MTF higher than 0.8 were obtained with little effect of the vertex distance. Increased image quality was obtained at an optimal pupil diameter and smaller field of view. Visual cortex activity data was recorded simultaneously with pattern projection, further highlighting the importance of the system for prosthetic vision studies. This novel head mounted projection system may prove to be a vital tool in studying natural and artificial vision in behaving animals.

Extending the depth of focus in tomography systems for glass lattice three-dimensional mapping.

This paper deals with the development of a computed optical tomography system designed and built to inspect glass lattices to locate various impurities inside the bulk. We focus on the investigation of the potential benefit in the usage of extended depth of focus optics for that application. The quality of 3D reconstruction for the application of glass lattice defect identification is tested numerically and experimentally against the corresponding result obtained with conventional optics.

Extended depth of focus intra-ocular lens: a solution for presbyopia and astigmatism

Purpose: Subjects after cataract removal and intra-ocular lens (IOL) implantation lose their accommodation capability and are left with a monofocal visual system. The IOL refraction and the precision of the surgery determine the focal distance and amount of astigmatic aberrations. We present a design, simulations and experimental bench testing of a novel, non-diffractive, non-multifocal, extended depth of focus (EDOF) technology incorporated into an IOL that allows the subject to have astigmatic and chromatic aberrations-free continuous focusing ability from 35cm to infinity as well as increased tolerance to IOL decentration. 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 (D stands for Diopters) with negligible loss of energy at any point of the focus while significantly reducing the astigmatic aberration of the eye and that generated during the IOL implantation. The EDOF IOL was tested on an optical bench simulating the eye model. In the experimental testing we have explored the characteristics of the obtained EDOF capability, the tolerance to astigmatic aberrations and decentration. Results: The performance of the proposed IOL was tested for pupil diameters of 2 to 5mm 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. Capability of correcting astigmatism of up to 1.00D was measured. Conclusions: The proposed EDOF IOL technology was tested by numerical simulations as well as experimentally characterized on an optical bench. The new lens is capable of solving presbyopia and astigmatism simultaneously by providing focus extension of 3.00D under various illumination conditions, wavelengths and pupil diameters of the implanted lens without loss of energy at any of the relevant distances.

Cortical adaptation and visual enhancement.

Passive ophthalmic optic devices correct refractive defects of the eye but are not designed to employ neural adaptation processes. An extended depth of focus technology is implemented on conventional refractive devices, such as spectacles and contact lenses, and its testing is described. This technology is capable of simultaneously correcting all refractive errors, such as myopia, hyperopia, presbyopia, regular/irregular astigmatism, as well as their combinations. This is achieved by exploiting the capacity of the visual system for adaptation to contrast as well as its capability of creating a coherent continuous visual field out of discrete lines of sight.

Computational expansion of imaging from visible to IR and gamma imaging systems

Lenses are used for imaging in a wide range of applications, but in many cases this leads to drawbacks. For example, in smart phone cameras the use of imaging lenses limits the flatness of the device, and in medical devices, such as micro-endoscopes, the field of view (FOV) is limited. In many applications, such as terahertz (THz) imaging—used for security purposes—or gammaray imaging, which is used in single-photon emission computed tomography (SPECT), conventional imaging lenses cannot be used. Instead, existing THz detectors require space scanning and bulky hemispherical lenses or mirrors,1 whereas gamma-ray imaging requires an array of collimators to allow only forwardpropagating rays to pass. We have found that the integration of a time-variable array of pinholes can be used to carry out high-resolution imaging. This array provides high energy efficiency if it is used to replace an imaging lens,2 and it can significantly extend the FOV3 if it is integrated into the aperture plane of an imaging lens. Avoiding the use of imaging lenses enables much flatter and cheaper imaging optics to be used in the visible and near-IR regions, and also in other spectral regions in which the use of conventional lenses is not feasible. Whether the array is used to replace a lens, or is integrated into a lens, its operating principle involves time-variable encoding of the aperture plane, followed by decoding to recover the resolution and FOV of the enhanced image. We have demonstrated experimental results for both the above-mentioned uses of the array.4 We achieved lens-free imaging by combining a variableaperture wheel, as shown in Figure 1, with a CCD sensor. Figure 1. Left: Variable-aperture wheel for use in combination with a CCD sensor to acquire images. Right: Experimental setup using the screen of a smartphone to display the imaged object.