Variability of wavefront aberration measurements in small pupil sizes using a clinical Shack-Hartmann aberrometer

BACKGROUND: Recently, instruments for the measurement of wavefront aberration in the living human eye have been widely available for clinical applications. Despite the extensive background experience on wavefront sensing for research purposes, the information derived from such instrumentation in a clinical setting should not be considered a priori precise. We report on the variability of such an instrument at two different pupil sizes. METHODS: A clinical aberrometer (COAS Wavefront Scienses, Ltd) based on the Shack-Hartmann principle was employed in this study. Fifty consecutive measurements were perfomed on each right eye of four subjects. We compared the variance of individual Zernike expansion coefficients as determined by the aberrometer with the variance of coefficients calculated using a mathematical method for scaling the expansion coefficients to reconstruct wavefront aberration for a reduced-size pupil. RESULTS: Wavefront aberration exhibits a marked variance of the order of 0.45 microns near the edge of the pupil whereas the central part appears to be measured more consistently. Dispersion of Zernike expansion coefficients was lower when calculated by the scaling method for a pupil diameter of 3 mm as compared to the one introduced when only the central 3 mm of the Shack – Hartmann image was evaluated. Signal-to-noise ratio was lower for higher order aberrations than for low order coefficients corresponding to the sphero-cylindrical error. For each subject a number of Zernike expansion coefficients was below noise level and should not be considered trustworthy. CONCLUSION: Wavefront aberration data used in clinical care should not be extracted from a single measurement, which represents only a static snapshot of a dynamically changing aberration pattern. This observation must be taken into account in order to prevent ambiguous conclusions in clinical practice and especially in refractive surgery

Comparison of Blue Light-Filtering IOLs and UV Light-Filtering IOLs for Cataract Surgery: A Meta-Analysis

Background: A number of published randomized controlled trials have been conducted to evaluate visual performance of blue light-filtering intraocular lenses (IOL) and UV light-filtering intraocular lenses (IOL) after cataract phacoemulsification surgery. However, results have not always been consistent. Therefore, we carried out a meta-analysis to compare the effectiveness of blue light-filtering IOLs versus UV light-filtering IOLs in cataract surgery. Methods and Findings: Comprehensive searches of PubMed, Embase, Cochrane Library and the Chinese BioMedical literature databases were performed using web-based search engines. Fifteen trials (1690 eyes) were included for systematic review, and 11 of 15 studies were included in this meta-analysis. The results showed that there were no significant differences in postoperative mean best corrected visual acuity, contrast sensitivity, overall color vision, or in the blue light spectrum under photopic light conditions between blue light-filtering IOLs and UV light-filtering IOLs [WMD = 20.01, 95%CI (20.03, 0.01), P = 0.46; WMD = 0.07, 95%CI (20.04, 0.19), P = 0.20; SMD = 0.14, 95%CI (20.33, 0.60), P = 0.566; SMD = 0.20, 95%CI (20.04, 0.43), P = 0.099]. However, color vision with blue light-filtering IOLs was significantly reduced in the blue light spectrum under mesopic light conditions [SMD = 0.74, 95%CI (0.29, 1.18), P = 0.001]. Conclusion: This meta-analysis demonstrates that postoperative visual performance with blue light-filtering IOLs is approximately equal to that of UV light-filtering IOLs after cataract surgery, but color vision with blue light-filtering IOL

Diffractive multifocal lens analysis using complex Fourier series

The diffraction efficiency of conventional diffractive lenses is typically analyzed using the complex Fourier series expansion coefficients. While conventional diffractive lenses typically target high diffraction efficiency in a single diffractive order, applications such as multifocal intraocular lenses seek high diffraction efficiency in multiple diffractive orders. Here, the complex Fourier series technique is generalized to handle these multifocal lenses, and applied to a novel trifocal intraocular lens design. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Multifocal Contact Lens HDR Image Simulation Showing Dysphotopsia

A system is developed for simulating the image quality and dysphotopsia of multifocal lenses. To achieve this, the simulation modifies a High Dynamic Range (HDR) photograph by blurring it with the lens' point spread function in MATLAB. Dysphotopsias are instances of unwanted or missing light within the eye. Common forms of dysphotopsia include glare, starburst (radial lines emanating from bright sources), and halo (rings of light surrounding bright sources) with the latter two typically occurring at night or in other high contrast settings. Dysphotopsia is considered the most common complaint of patients after successful cataract surgery and have thus earned significant attention in the context of intraocular lenses (IOLs). There have been fewer studies of multifocal contact lens dysphotopsia, but this is despite the documented impact dysphotopsia has on the image quality of multifocal lenses. This simulation is the first handling of dysphotopsia that combines HDR images and specifics of the lens design to predict how the dysphotopsia will appear to patients. Being able to show patients accurate simulations of dysphotopsia has the benefit of setting proper patient expectations before they begin using multifocal lenses. Furthermore, these simulated images can also potentially help diagnose patient problems by giving patients an accurate baseline to compare to. © 2022 SPIE. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Generalized surface reconstruction and fringe analysis through phase measuring deflectometry

A deflectometry simulation system for measuring and generating the surface profiles of freeform optical elements was designed. Unlike alternative optical metrology methods, deflectometry systems utilize the principle of pixel to pixel point mapping to measure a specular optical surface. The in-lab set up uses readily available materials such as an LCD monitor, a CMOS camera, and other basic lab items such as optical posts and post holders. A software that enlists the usage of phase unwrapping in order to derive the incident and reflected light vectors from a surface under test. These vectors provide slope information which can then be integrated into a surface reconstruction. This allows for a non-contact surface reconstruction method as well as a simulation to help calculate the best respective placements of monitor, camera, and test surface. This type of system is useful in a measuring more challenging optical surfaces such as free forms and convex optical surfaces. Disclosures of the system and distance sensing lasers could enable a very user friendly and intuitive handler experience for creating the surface reconstruction profiles with much more reliable system geometry information and reduction of excess light and scattering noise. Multi rotation stages can also be used for adjusting tip and tilt angles of test surfaces. © 2022 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Through focus point spread function and modulus transfer function for multifocal lenses

A system for measuring the through-focus point spread function (PSF) for intra-ocular lenses (IOLs) and converting to modulation transfer function (MTF) is developed. The system consists of a light source, eye model, IOL, magnifier, and CCD camera. By capturing the resulting image through a range of focus positions, the PSF is found and converted to MTF. The MTF displays differences in the depth of focus for monofocal, multifocal, and extended depth of focus (EDOF) IOLs. As multifocal and EDOF IOLs evolve, using the MTF to predict the image quality is vital to implanting the most appropriate lens in the patient's eyes. © 2022 SPIE. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Single-Shot Intraocular Lens Surface Measurement With The GelSight Topography System

The intraocular lens (IOL) industry is continuously evolving with more complex surface designs that require affordable and timely surface measurements of extended depth of focus (EDOF) and diffractive multifocal lenses. Current systems to measure grating profiles, such as AFM, SEM, or optical profilometers are expensive, need intensive training, and are sometimes destructive. Furthermore, the fields of view of these systems are typically limited, so measuring the full aperture of the lens requires repeated measures and stitching of the result. The system developed allows for quick profile measurements with easy to obtain equipment that will help examine and develop diffractive multifocal IOLs. This study integrates a 3D GelSight camera (GelSight, Inc, Waltham, Massachusetts), a stepper motor, and an Arduino board with driver board to automate the measurement of IOL gratings. The GelSight 1.0X camera has a height resolution of 1.0 µm and is provided with software that will be used to select and export data from areas of interest. Post processing will be required to analyze the data from the GelSight, but can be customized to the user’s needs. Using simple Arduino code and a stepper motor to move the camera onto the sample allows for a hands-free measurement technique that promotes accuracy and repeatability. Automation allows for beginners to quickly use the newly proposed system for many profile measurement applications with little setup time. The system will benefit the development of IOLs as a quick and easy check for the production process of these advanced lens designs. © 2022 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Goldmann tonometry tear film error and partial correction with a shaped applanation surface

Sean J McCafferty,1–4 Eniko T Enikov,5 Jim Schwiegerling,2,3 Sean M Ashley1,3 1Intuor Technologies, 2Department of Ophthalmology, University of Arizona College of Medicine, 3University of Arizona College of Optical Science, 4Arizona Eye Consultants, 5Department of Mechanical and Aerospace, University of Arizona College of Engineering, Tucson, AZ, USA Purpose: The aim of the study was to quantify the isolated tear film adhesion error in a Goldmann applanation tonometer (GAT) prism and in a correcting applanation tonometry surface (CATS) prism.Methods: The separation force of a tonometer prism adhered by a tear film to a simulated cornea was measured to quantify an isolated tear film adhesion force. Acrylic hemispheres (7.8 mm radius) used as corneas were lathed over the apical 3.06 mm diameter to simulate full applanation contact with the prism surface for both GAT and CATS prisms. Tear film separation measurements were completed with both an artificial tear and fluorescein solutions as a fluid bridge. The applanation mire thicknesses were measured and correlated with the tear film separation measurements. Human cadaver eyes were used to validate simulated cornea tear film separation measurement differences between the GAT and CATS prisms.Results: The CATS prism tear film adhesion error (2.74±0.21 mmHg) was significantly less than the GAT prism (4.57±0.18 mmHg, p<0.001). Tear film adhesion error was independent of applanation mire thickness (R2=0.09, p=0.04). Fluorescein produces more tear film error than artificial tears (+0.51±0.04 mmHg; p<0.001). Cadaver eye validation indicated the CATS prism’s tear film adhesion error (1.40±0.51 mmHg) was significantly less than that of the GAT prism (3.30±0.38 mmHg; p=0.002).Conclusion: Measured GAT tear film adhesion error is more than previously predicted. A CATS prism significantly reduced tear film adhesion error by ~41%. Fluorescein solution increases the tear film adhesion compared to artificial tears, while mire thickness has a negligible effect. Keywords: glaucoma, intraocular pressure, IOP, Goldmann, bias, error, tonometer, applanation, tear fil

Remote measurement of sphero-cylindrical lens power and orientation through distortion analysis

A system for measuring the orientation and power of sphero-cylindrical lenses has been developed. The system attempts to minimize the need for specialized equipment and training and instead relies on the ubiquitous cell phone camera, a magnetic stripe card, and a target pattern. By capturing an image of the target through the lenses under test and analyzing the distortion in the resulting image, the orientation and powers on sphero-cylindrical lenses can be determined. In modern eye clinics, the measurement of sphero-cylindrical spectacle lenses is readily measured with a lensmeter. However, there are many examples where this measurement is not feasible. This may include remote or rural locations where access to eye care may not exist, or require impractical travel. Furthermore, the on-going global pandemic has often put restrictions on contact between the patient and the eye care provider. Telemedicine, which can connect patients to eye care providers, lacks physical access to the spectacles for measurement. The system developed in this effort overcomes this limitation by allowing remote measurement of the lenses with items found in most households. Such a system would be beneficial to often underserved populations and expand access to quality eye care. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]