bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Peripheral Optical Quality on Spatial Contrast Sensitivity
Authors: Coletta Nancy J. , Sharma Vineeta , Carter John
Published: February 2023

The optical quality of the human eye is best for central vision and worsens for peripheral viewing conditions; most observers exhibit marked astigmatism for off-axis viewing (Jennings and Charman, 1981; Navarro, Artal and Williams, 1993). Whether or not correction of peripheral refractive error improves visual performance seems to depend on the visual task. For example, visual acuity may not increase with peripheral correction but perimetric thresholds can be improved (see discussion in Jennings and Charman, 1981).
Human Face Recognition Using Wavelets
Authors: Lakshminarayanan Vasudevan , Bhatia Sanjiv K. , Welland Grant V. , Sama Ashok
Published: February 2023

Face perception and identification is a task done routinely by all of us. Considerable research has been carried out psychophysically on the detection and identification of human face and sophisticated models have been developed [2]. A critical issue in processing human faces in a machine vision system is the representation of a face since this determines the amount of storage of facial image. In general, a common technique is storing a 2-dimensional array of intensity values as an image file and then compressing the image (e.g. GIF, JPEG compression standards). It is also possible to degrade the image to lower spatial and grayscale resolution. However, at some point reducing resolution (number of pixel blocks) will be counterproductive due to significant loss of information. Here, we report the results of systematic and extensive psychophysical experiments to determine the precise limits of resolution (both spatial and grayscale) for face perception.
The Role of Photon Noise in Determining Visual Threshold
Authors: Reeves Adam , Wu Shuang
Published: February 2023

The purpose of the research was to determine the role that photon noise plays in setting the increment threshold, using an idea introduced by Krauskopf and Reeves (1980). The state of photoreceptor and neural adaptation is fixed by exposure to a steady adapting light. The role of photon noise is then deduced by comparing thresholds for test flashes on the adapting field (‘ON’ thresholds) with thresholds obtained just after the field has been turned off (‘OFF’ thresholds).
Temporal characteristics of the motion aftereffect differ in the fovea and periphery
Authors: Chen Yue , Tripathy Srimant P. , Bedell Harold E.
Published: February 2023

Sensitivity to moving stimuli varies systematically as a function of retinal eccentricity. For instance, the threshold for detecting motion (Johnston & Wright, 1983, 1985), the maximum and minimum displacements compatible with stroboscopic motion (Baker & Braddick, 1985), and the speeds at which velocity discrimination is optimal (McKee & Nakayama, 1984) all increase as a function of retinal eccentricity. These changes in motion processing with eccentricity are not surprising, because of the marked inhomogeneity of spatial processing across the visual field.
Stability of Target Fixation
Authors: Bolzani R , Campos EC , Dickmann A , Enoch JM
Published: February 2023

High resolution commercially available devices allow measurement of small eye movements during target fixation. Preliminary results are presented of an experimental study whose aim is to analyze relations between target characteristics and stability during fixation with and without a second randomly located peripheral target, in binocular and monocular vision. The initial data are collected from a binocular testing without a second peripheral target.
Modeling the Optical Properties of the Aging Human Crystalline Lens from Computer Processed Scheimpflug Images in Relation to the Lens Paradox
Authors: Cook Christopher Andrew , Koretz Jane F.
Published: February 2023

Of the many methods that have been developed (e.g., phakometry, NMI, etc.) for non-invasive measurement of the geometry of the anterior segment, at present Scheimpflug photography offers the best resolution and the highest accuracy. The primary obstacle encountered with this or any other image based method has been obtaining quantitative measurements of the position and curvature of lens surfaces and zone boundaries from the images directly. Image enhancement (Sobel gradient scanning), and pattern recognition methods (Hough transformation and recursive least squares algorithms) have been applied successfully to this problem. These techniques have been described previously [1] as well as the algorithms used to correct for nonuniform Scheimpflug camera scaling. Combined, these techniques yield representations of lens geometry having sufficient accuracy that ray tracing can be applied to determine lens optical properties from well poised models with one unknown. The image processing methods will be reviewed as an introduction.
Occupational Psychophysics: Establishing Job-Related Vision Requirements
Authors: Johnson Chris A.
Published: February 2023

A number of occupations have established vision standards or requirements that must be met by job applicants. Many of these vision requirements have either been adapted from military standards, from expert opinions of vision specialists, or from a historical precedent of undetermined origin. Only a few occupational vision standards have been based on research directed towards empirically-defined measures of performance (Giannoni, 1981; Good and Augsburger, 1987; North, 1993, Sheedy, 1980). With the recent advent of the Americans with Disabilities Act (ADA), it has now been mandated that physical requirements for specific occupations must be based on validation studies that pertain to performance of essential job functions. Expert opinion is no longer sufficient to justify or defend occupational standards for vision.
Effects of retinal illuminance on a temporal gain control in the flicker ERG
Authors: Wu Shuang , Burns Stephen A.
Published: February 2023

According to Kelly's analysis (1961) of the psychophysical measurements of flicker thresholds, human visual sensitivity is inversely proportional to the mean light level at low temporal frequencies (i.e., ΔI/I = constant, Weber's Law), but is mostly determined by absolute amplitude of modulation (ΔI) at high temporal frequencies. This pattern of response was later replicated in electrophysiological measures of retinal responses, such as in monkey ganglion cells (Purpura et al., 1990) and in the human focal electroretinogram (Seiple et al., 1992). From the electrophysiological results it has been suggested that the temporal frequency dependent adaptation must occur at the retinal level, and in the case of Seiple et al's study, at the level of the photoreceptors. However, the relation of this frequency- dependent adaptation pattern to the modulation depth of the flickering stimulus has not been characterized. In a previous study (Wu et al., 1993) we found that the flicker ERG exhibited a nonlinear frequency dependent adaptation. In this study we further investigate the relation of the frequency dependent adaptation to luminance adaptation at different modulation depths. Since the flicker ERG is nonlinear at all modulations (Burns et al., 1992), and the relation of response amplitude to modulation varies nonlinearly across frequencies (Wu et al., 1994), characterization of the temporal response of the system requires response measurements at a series of modulations and luminance levels. In this study we report results from such measurements, and relate the temporal frequency adaptation results to those from several classic luminance adaptation studies.
Monocular vs Binocular Visual Acuity as Measures of Vision Impairment
Authors: Rubin Gary S. , Muñoz Beatriz , Fried Linda P. , West Sheila K.
Published: February 2023

The Salisbury Eye Evaluation (SEE) was initiated in the 1992 as a multi-disciplinary study of eye disease, vision impairment, and physical disability in older Americans. A representative sample of 2300 adults between the ages of 65 and 84 will participate in the study, one component of which is a prospective evaluation of the relationship between specific measures of visual function and the individual’s ability to perform everyday visual tasks such as read the newspaper, recognize faces, navigate independently, and use the telephone.
Closed Road Driving Performance: Effect of Degradation of Visual Acuity
Authors: Higgins Kent E. , Wood Joanne , Tait Alan
Published: February 2023

It is virtually impossible to read the literature on driving without encountering a statement to the effect that 90% of the information required for driving is “visual”. From such a perspective, the prevalence of the 20/40 visual acuity criterion for unrestricted driver licensure seems understandable (e.g., Bailey & Sheedy, 1988). A critical question, however, is whether this, or any of the existing vision standards for licensure, can be defended by reference to empirical evidence. Answers to such questions will become increasingly important as an increasing proportion of the population fails to meet existing standards due to normal aging and/or age-related ocular disorder.
Visual Acuity and Contrast Sensitivity For Individual Sloan Letters
Authors: Alexander Kenneth R. , Xie Wei , Derlacki Deborah J.
Published: February 2023

Letter optotypes such as Sloan letters (NAS-NRC, 1980) are typically used in the clinical assessment of spatial vision, and scoring procedures are usually based on the number of individual letters that are identified correctly (e.g., Bailey et al., 1991; Elliott et al., 1991). This approach assumes that all Sloan letters have approximately equal identifiability, but there is some disagreement on this point (e.g., Elliott et al., 1990; Robson et al., 1990; Ferris et al., 1993). This may be due to the method used to assess identifiability. Typically, previous studies have assessed letter identifiability by measuring percent correct at threshold; relatively few have examined thresholds per se. Depending on the nature of the underlying psychometric function, these two approaches may not provide equivalent estimates of relative letter identifiability.
Refractive Index of the Ocular Lens is altered by Scattered Light
Authors: Hemenger Richard P.
Published: February 2023

As the crystalline lens ages it undergoes a number of changes having optical consequences. These might include substantially increased amounts of absorbed and scattered light as well as increased surface curvatures. Apparently the refractice index also changes with age but why or how it happens is currently under debate. The 'lens paradox', a name given to the observation that surface curvatures of the average lens increase with age while its refractive power doesn't change, is resolved by postulating an appropriate change in refractive index. For example, a small increase with age of the index in the lens cortex accomplishes the desired end1. Another interesting observation is the apparent increased refractive power of lenses subsequent to nuclear sclerosis and nuclear cataract2. Increased refractive index in the lens nucleus is a possible explanation.
In Vitro Method for Integrated Angular Light Scattering Measurements in Eye Lenses
Authors: Thaung Jörgen , Abrahamsson Maths , Sjöstrand Johan
Published: February 2023

Many investigators have attempted to quantitively measure the light scattering from extracted eye lenses. Several different techniques have been used, for example: Söderberg et al1 used a rather simple method (a camera light-meter) and detected large angel scattering, Sivak et al2 designed a scanning laser system that used the detected error in the refraktive properties of the lens, which could be considered as small angel scatter.
Cone Photoreceptor Directionality and The Optical Density of the Cone Photopigments
Authors: Burns Stephen A. , Wu Shuang , Elsner Ann E.
Published: February 2023

It is well known that the structure of the retina changes rapidly away from the center of the fovea. The cones become wider and shorter, and rods are present within the photoreceptor array. To examine the effect of changes in retinal structure with retinal eccentricity, the current paper compares the properties of the retinal photoreceptors as a function of retinal position. These measurements of the structural and functional properties of the foveal cone photoreceptors are important for both clinical and basic research questions. Clinically it is known that cone photopigment density is reduced by a number of disease processes. In addition the alignment of the cones towards the center of the pupil of the eye is also affected by a number of diseases1-4. In addition, a number of laboratories have begun investigating new techniques for imaging the photoreceptors in vivo5-6. These techniques typically require capturing the light exiting the eye and either correcting for the aberrations caused by the optics of the eye, or using coherent techniques that are less affected by the optics of the eye. These techniques require using a moderately large pupil (5-8 mm) to obtain the necessary resolution. However, we have shown that if light is collected over the entire pupil, then some of the light has been guided back out of the eye by the cone photoreceptor optics, and the other portion has been scattered. Since the directed light occupies only a portion of the pupil area, techniques dependent on light returning from the retina may be affected by variations in the waveguide properties of the cones with variations of retinal position.
Effects of Dioptric Blur on the Visual Performance of Myopic and Emmetropic Young Adults
Authors: Thorn Frank , Cameron Linda , Arnel Jonathan , Thorn Sondra
Published: February 2023

Animal studies on the etiology of myopia demonstrate that pattern deprivation can induce axial myopia. Dioptric blur induced by ophthalmic lenses can also alter the axial growth of the eye, with the growth rate increasing or slowing to counteract the blur induced by the lenses. In this case, negative lenses induce axial myopia but this myopia can readily be reversed to emmetropia by removing the lenses during the animal’s growth phase. Speculation exists that accommodative inaccuracies may induce blur in otherwise normal animals, and that this blur may in turn induce or exacerbate myopia progression.
A Telescopic Bifocal for Low Vision
Authors: Spitzberg Larry , Reich Lewis , Chen Shaui , Qi Ming , Kuether Christian
Published: February 2023

A series of new telescopic bifocals have been designed and produced as part of a spectacle lens. These units provide longer working distances than conventional bifocals of the same equivalent power while incorporating many advantages over current low vision telescopes. Since the telescopes are integral with the spectacle lens, these units are easily aligned for binocular viewing with the patient’s spectacle prescription (Rx) placed on the back surface in a manner similar to conventional bifocals.
PAL performance analysis for torical prescription
Authors: Baudart T.
Published: February 2023

Progressive-Addition Lenses (PAL) are commonly designed for non-astigmatic lens wearers, yet a large proportion of the population requires toric correction. Moreover, the optical performances of PAL are always given for lenses with spherical prescription. In fact, the charts of optical performances for PAL with toric prescription are not easy to interpret because of the combination of astigmatism induced by the progressive surface, the toric surface, and the obliquity of light rays.
Evaluation of the Dry-Eye Tear Film Using Thin Film Interferometry
Authors: Doane Marshall G.
Published: February 2023

Apart from its optical duties as the initial refracting surface of the eye, the preocular tear film serves as a major protective environment for the cornea. The tear layer provides a depot of dissolved oxygen and other metabolites, affords a pathway for "used" metabolic products to escape the cornea, and, with its complement of biochemical agents, acts as a formidable defense against invading micro-organisms. To facilitate these functions, it is imperative that the surface of the eye be kept moist, and the extreme discomfort accompanying even short periods of surface dryness provides evidence of the importance of maintaining this thin layer of fluid on a continuous basis.
Visual Performance Under Dilated Conditions Following Excimer Photorefractive Keratectomy
Authors: Casson E. J. , Jackson W. B. , Mintsioulis G. , Norton S. , Munger R. , Strolenberg U.
Published: February 2023

The goal of photorefractive keratectomy (PRK) is to correct refractive error permanently and provide patients with optimized visual performance without corrective lenses. If high contrast visual acuity is used as the measure of visual performance, numerous studies can document the stability and predictability of PRK, particularly for mild to moderate myopes. The vast majority of individuals in these studies remain within one line of their pre-operative, best-corrected acuity, while greatly improving their uncorrected visual acuity.1-4
Ray Tracing in the Living Eye with a Laser Beam. Spot Diagrams and Aberrations
Authors: Navarro Rafael , Losada M. Angeles
Published: February 2023

Optical designers usually compute ray tracing and spot diagrams to predict theoretically the performance and image quality of an optical system. Sivak and Kreuzer [1] implemented an elegant physical ray tracing method for excised lenses, using laser pencils, although their technique could not be implemened in vivo. Until recently, we have been using a double pass method to measure the modulation transfer function of the living eye [2]. Last year, based on that method, we presented a substantially modified technique that we called one and a half pass method [3]. The illuminating beam consists of a narrow Gaussian pencil so that the image formed on the retina is a diffraction-limited Gaussian. This allows us to measure the phase transfer function, and then estimate the retinal point spread function. Here we show a new modification of this method that allows a direct and objective measurement of geometrical ray aberrations in the living eye.
Visual Acuity Development of Term Infants Fed ω3 Long Chain Polyunsaturated Fatty Acid (LCPUFA) Supplemented Formula
Authors: Birch Eileen , PhD Dennis Hoffman , Birch David , Uauy Ricardo , Bane Mark , Castañeda Yolanda , Prestidge Claude
Published: February 2023

While breast-feeding provides optimal nutrition for healthy infants, maternal health, social, and/or economic factors may constrain a mother's ability to provide human milk. Formula feeding provides a safe and effective alternative source of nutrition. In response to ongoing research, formula composition is revised to more closely mimic human milk in providing essential nutrients to support optimal growth and development. During the last decade, supplementation of infant formula with ω3 long chain polyunsaturated fatty acids (LCPUFAs) has been a major focus of infant nutrition research. ω3 LCPUFAs, particularly docosahexaenoic acid (DHA), are found in extremely high concentration in photoreceptor outer segments and in cerebral cortex.
Vision function of the oldest-old
Authors: Brabyn John , Schneck Marilyn , Haegerstrom-Portnoy Gunilia
Published: February 2023

People over the age of 65 are the fastest growing segment of the population with those over 85 years increasing even faster. Many previous studies have reported on changes in multiple vision functions with age (e.g. Häkkinen, 1984, Bergman et al. 1992, Rubin et al., 1995). In most previous studies, the oldest-old are often not well-represented. We are currently in the process of assessing vision function on a large battery of tests in a community dwelling older population living in Marin County, California. The randomly selected population which has been followed longitudinally for other epidemiological studies consists of over 2000 people over the age of 55 year (Reed et al. 1995). The oldest-old are over-represented with 500 participants over the age of 85 in the initial sample. Over 800 participants of the 2000 have participated in the vision study conducted in cooperation with the Buck Center for Research in Aging. The battery includes measure of spatial vision, temporal vision, reading performance, glare sensitivity, glare recovery, color vision, binocular vision, motion sensitivity, and central and peripheral visual fields including attentional visual fields. A subset of vision test results are presented here from a subset of the total sample. Only people 75 years and over are included. A total of 372 individuals with an average age of 83 years (s.d. 5.8) have completed the test battery to date. Of these, 121 are 85 years of age or older.
Isolation of Pupil Light Reflex Response Components: Selective Loss of Function in a Subject with Optic Nerve Drusen
Authors: Barbur John L , Cole Vicky A , Harlow J A , Levy Ivor S
Published: February 2023

The ambient light level determines largely the steady-state size of the pupil (Lowenstein et al, 1964) and rapid increments in light flux on the retina cause a brisk constriction of the pupil that is often described as the dynamic light reflex response (Alexandridis, 1985; Lowenfeld, 1993). The afferent pathways that control the steady-state size of the pupil and the dynamic light reflex response in man have been associated with subcortical projections and this is consistent with clinical observations which suggest that the pupils continue to respond normally to sudden changes in room illumination even when the patients are cortically blind (Brindley et al, 1969). It is of great interest to investigate whether the same afferent pathway controls both the steady-state and the dynamic light reflex response in man. Analysis of pupil response curves measured as a function of luminance contrast when long duration stimuli are employed suggests that two independent principal components are sufficient to account for the family of curves that describe the observed pupil responses. These components have been labelled sustained and transient (Young et al, 1993; Young & Kennis, 1993). A number of pupil studies have demonstrated the absence of Pupil Light Reflex (PLR) responses in patients with post-geniculate lesions when small test stimuli are employed (Harms, 1951; Cibis et al, 1975; Barbur et al, 1988; Kardon, 1992; Kardon et al, 1993). Such observations suggest that more than one afferent pathway is involved in the control of the pupil response to light and that these pathways may not be entirely subcortical. A better understanding of the visual pathways involved and the kind of visual stimulus characteristics that cause pupillary responses will undoubtedly increase the usefulness of pupil based tests in neurologic and ophthalmologic examinations. With this in mind we have developed background perturbation techniques (Cole et al, 1995) that attempt to isolate different components of the PLR response. Preliminary findings are reported in normal subjects and in a patient with optic nerve drusen. The results suggest that the PLR is driven by at least two components. One component that integrates light flux changes over large areas of the visual field and determines largely the size of the pupil and a second component that dominates the response when small stimuli are involved and contributes significantly to the dynamic PLR response. This component is likely to be absent in patients with post-geniculate lesions.
The Rising Phase of Rod Photocurrent is Fitted by a Linear Model of the Molecular Cascade with No Absolute Delay
Authors: Hamer Russell D. , Tyler Christopher W.
Published: February 2023

A good understanding of the mechanisms of rod transduction is important in the diagnosis of retinal diseases affecting rod function. One well-characterized transduction pathway is that of vertebrate phototransduction, as exemplified by the analysis by of the activation processes in rod phototransduction based on biophysical and biochemical considerations. Taking such an approach to the analysis of salamander rod photocurrent responses, Lamb & Pugh (1992) conclude that the rising phase is well-described as an absolute delay followed by an inverted Gaussian acceleration. This model has been shown to provide a good fit to the rising phase of the photocurrent in amphibian rods (Lamb & Pugh, 1992), as well as to the rising phase of the a-wave of the ERG in humans (Hood & Birch, 1993; Hood & Birch, 1994; Breton et al., 1994). The model was linear up to ~104 photoisomerizations (Φ) per flash, above which progressive nonlinear changes in the model parameters were required to fit the data.
Recovery Kinetics of Human ROD Photoresponses: A Model Suggested by The Two-Branched a-WAVE "Saturation Function"
Authors: Pepperberg David R. , Birch David G. , Hofmann Klaus Peter , Hood Donald C.
Published: February 2023

Recovery of the human ERG a-wave can be tracked using a paired-flash protocol, in which the test flash is followed at varying times by a bright probe flash that saturates the rods. Birch et al.1 used this approach to measure the period (T) of apparent saturation of the rod-mediated a-wave2 in relation to the intensity (If) of the test flash. Fig. 1 shows the "saturation function" (T vs. ln If function) obtained in a group of experiments. Over the investigated range of If (40 to 106 scot-td-s), the saturation function exhibits two essentially linear branches, the slopes of which [ΔT/Δ(ln If)] are ≃0.3 s and ≃2.3 s. Results obtained in studies of salamander rods3-5 led Birch et al. to hypothesize that the upper-branch slope of 2.3 s represents "τR*", the exponential lifetime of photoactivated rhodopsin (R*). The occurrence of two branches in the saturation function of Fig. 1 could in principle reflect a variation of τR* with flash intensity, i.e., an increase of τR* from -0.3 s to =2.3 s with increasing If. However, the evidence that τR* in salamander rods is unaffected by changing illumination conditions3-6 suggests that τR* in human rods may be constant. Here we present a model of rod transduction based on the assumption that τR* is constant. We show that this model can account for the two-branched property of the a-wave saturation function.
The Effects of Gaussian Noise on the Videokeratoscopic Measurement of Spherical Equivalent Power
Authors: Schwiegerling Jim , Greivenkamp John E.
Published: February 2023

One of the questions surrounding the use of videokeratoscopic height data is the ability to extract useful parameters in the presence of noise. Parameters such as spherical equivalent power, radius of curvature and conic constant need to be accurately calculated from noisy height data. There have been suggestions that submicron accuracy of the corneal height is required to faithfully determine quantities such as axial and instantaneous power.1 This accuracy requirement, however, appears stringent and further examination of height precision is necessary.
Predicting Variations in Visual Performance caused by Optical Defects - 2
Authors: Strang Niall C , Atchison David A , Woods Russell L
Published: February 2023

Modelling of the effect of defocus on the contrast sensitivity function (CSF) predicts a non-monotonically decreasing function characterised by multiple local minima (notches).1,2 The notches are a consequence of defocus and aberration on the modulation transfer function (MTF). A recent study by our group1,2 demonstrated that, for 6mm pupils, the shape of defocussed CSFs and in particular the position (spatial frequency) and depth of notches could be predicted from the measured ocular aberration. Notches were well predicted and repeatable for hyperopic (negative) defocus, but predictions were less reliable for myopic (positive) defocus.
Clinical Investigation of Soft Contact Lenses with Compensated Spherical Aberration for Correcting High Ametropia
Authors: Chateau Nicolas , De Brabander John , Bouchard Florence , Guidollet Sandrine
Published: February 2023

In conventional contact lenses, the spherical shape of both anterior and posterior optical surfaces induce spherical aberration. With lenses of higher back vertex power (BVP), previous calculations1,2,3,4 and in-vitro measurements5 suggested that the level of aberration could significantly degrade the retinal image.
Harmonic Analysis of the Strobe Flicker Electroretinogram in Retinal Disease
Authors: Alexander Kenneth R. , Levine Michael W. , Fishman Gerald A.
Published: February 2023

The electroretinogram (ERG) elicited by a flickering stimulus has become a useful clinical test for monitoring the progression of retinal disease and for inferring the pathophysiology of the disease process. In the clinical setting, the flicker ERG is usually obtained using a train of strobe flashes. The effect of the disease process is then either derived from an examination of the characteristics of the flicker ERG waveform, such as peak amplitude and implicit time, or from narrow-band filtering of the ERG at the stimulating frequency. However, the interpretation of the flicker ERG can be problematic in cases of retinal disease in which patients have unusual waveform shapes. An example is the double-peaked 30 Hz flicker ERG waveform reported by Miyake et al. (1987) in patients with "incomplete" congenital stationary night blindness (CSNB). We recently identified two patients with typical retinitis pigmentosa (RP) who showed also showed a double-peaked flicker ERG waveform, indicating that this response abnormality may be found in other types of retinal disorders besides incomplete CSNB. The purpose of the present study was to characterize the harmonic components of the flicker ERG in these RP patients in order to better understand the origin of this anomalous flicker response as well as the flicker ERG of normals.
New Developments toward a Clinical Test of Retinal Ganglion Cell Function
Authors: Bearse Marcus A. , Sutter Erich E. , Palmowski Anja M.
Published: February 2023

We recently developed a method for extracting a component from the human multifocal electroretinogram (ERG) that is generated by ganglion cells1,2. As its latency depends linearly on the estimated length of ganglion cell axons connecting the site of focal stimulation with the disc, this optic nerve head component (ONHC) is presumed to originate from the axons where myelination begins1,2. A second, retinal component (RC) has an invariant latency.
Spherical Aberration of the Crystalline Lens
Authors: Smith George
Published: February 2023

Knowledge of the aberration properties of the lens are important for at least two reasons; (1) it gives some indication of the limitations of using corneal distortions alone as a measure of total ocular aberration and (2) it will help us unravel the gradient refractive index structure of the lens. In this paper we will use published data on ocular aberrations and corneal shape to estimate the spherical aberration of the lens. By comparing this data with predictions from equations for the spherical aberration of gradient index materials, we will examine possible forms of the gradient index structure of the lens.
Confocal Scanning Laser Ophthalmoscope for Real-Time Photoreceptor Imaging in the Human Eye
Authors: Roorda Austin , Campbell Melanie C.W. , Atkinson Matthew R. , Munger Rejean
Published: February 2023

The Waterloo CSLO(1) has been set up to facilitate the viewing of individual photoreceptors in the living human retina.
Identification of Convergence Accommodation in Infants Aged 3 to 6 Months
Authors: Bobier William R. , Guinta Austin , Kurtz Stacey , Howland Howard C.
Published: February 2023

As with many other visual functions, ocular accommodation and vergence show rapid development in the first 6 months of life.1-6 When convergence and accommodation are measured separately on the same child, evidence suggests that the two systems are not correlated in their responses until at least 2 months of age.7,8 There is little information on the early development of the cross links between accommodation and vergence, specifically accommodative vergence and vergence-driven accommodation. One study has been conducted on the development of accommodative vergence.9 In that study, Aslin and Jackson found convergence could be elicited when infants between 2 and 6 months of age monocularly viewed a target that was changing in depth. Although this is strong evidence for the existence of accommodative-driven vergence, the possibility remains that vergence was driven by proximity cues having different inputs than blur-driven accommodation.10 The purpose of our study was to determine if the convergence accommodation cross link was present in infants aged 3 to 6 months.
The Influence of Defocus-Induced Myopia and Hyperopia on Serotonergic and Dopaminergic Amacrine Cells in Chick Retina
Authors: Wong S.T. , Bakelaar A.J. , Ball A.K. , Callender M.G. , Sivak J.G.
Published: February 2023

It has been two decades since refractive errors were first induced in monkeys using lid-suture techniques1. Experimental myopia has been produced subsequently in various animal species including tree shrews2, kittens3, and birds4. The domestic chicken is used extensively in myopia and hyperopia research since these animals develop rapidly and display extremely high visual capabilities. Myopia can be artificially induced in young chicks using a variety of techniques including lid-suture5, intra-ocular injections6, translucent occluders7, and concave lenses8. Hyperopia can be produced by rearing animals in complete darkness9 or by the application of convex lenses8,10.
Methods for Determining The Power Of The Human Lens
Authors: Atchison David A. , Smith George
Published: February 2023

The human lens is a gradient refractive index structure that changes its shape on accommodation and grows throughout life. To understand the effect of these changes on the optical properties of the lens, we need to understand how the gradient refractive index affects lens power and aberrations. We cannot use conventional paraxial ray tracing to find lens power.
Foveal Cone Photopigment Distribution in Age-Related Macular Degeneration: Association with Fundus Features
Authors: Elsner A.E. , Moraes L. , Kunze C.W. , Hartnett M.E.
Published: February 2023

The chief cause of blindness among adults in the U.S. (1) is currently age-related macular degeneration (AMD), which affects the photoreceptor/retinal pigment epithelial (rpe) complex.
Corneal topography volume maps for predicting rigid contact lens centration and motion
Authors: Klein Stanley A. , Corzine John , Kung Jonathan
Published: February 2023

For a rigid contact lens to perform well on an eye, several criteria must be met (Mandell, 1988).
Field Expansion for Homonymous Hemianopia using Prism and Peripheral Diplopia
Authors: Peli Eli
Published: February 2023

Visual field loss following a cortical lesion from stroke, brain surgery, or head trauma frequently manifests as homonymous hemianopia. Hemianopic field loss causes problems in mobility and navigation as well as reading. Patients frequently complain of bumping into obstacles on the side of the field loss and getting bruised on their arms and legs. The number of such accidents decreases with adaptation to the condition, presumably because patient are getting more cautious and use head and eye scanning techniques to avoid the pain. Despite such improvements many patients continue to suffer from the effects of limited visual field. Of great concern to many patients and vision rehabilitation personnel is the question of driving with such field defect. In all states where visual field requirements for driving are legislated, such field loss will disqualify drivers, unless qualified by special testing and licensing.
Temporal modulation thresholds isolate mechanisms with different adaptational and spatial properties
Authors: Vingrys Algis J , Demirel Shaban
Published: February 2023

Temporaland spatial properties of a stimulus visual can be used to isolate different visual pathways (sustained and transient) which are thought to be mediated by different neuronal sub-populations (M- and P-cells) in humans. Temporal modulation has been used to detect early visual dysfunction by way of flicker modulation thresholds or frequency doubling (Casson et al., 1993: Johnson & Samuels, 1997). In these cases it has been assumed that flicker detects losses by targeting sub-populations of neurones.
Characteristics of Reading Speed across Character Size in Relation to Visual Factors
Authors: Schuchard Ronald A. , Lim Jung Min , Fletcher Donald C.
Published: February 2023

Reading performance is becoming a de facto standard for assessment of functional vision especially with respect to low vision function. This emphasis on reading performance has encouraged the development of new tests of reading vision such as the MNREAD Acuity Chart, Pepper Test, and Morgan Test. MNREAD Acuity Charts were designed so they can be used to quantify reading speed across a range of sentence character sizes in patients with normal and low vision. Previous studies have found that MNREAD measures of reading acuity, critical print size, and maximum reading speed are very useful indices for characterizing reading abilities in patients with low vision (Bane, Fish et al. 1996; Mansfield, Legge et al. 1996). However, the results of the MNREAD Acuity Chart can give the complete functional relationship between reading speed and character sizes. Clinically we have found that there is considerable differences in the rise (or slope) of the function from no reading ability to maximum reading ability. In addition, the length of the maximum reading speed plateau and whether the reading speed decreases at larger character sizes also has considerable variability. The significance of these characteristics of the reading speed curve to reading training has not been thoroughly investigated, but intuitively these characteristics would have significance in reading training. For example, the amount of magnification that is prescribed for reading would be more or less critical depending on the slope of the reading speed curve and the length of the maximum reading speed plateau. Also, if visual factors influence the reading speed curve than it might be possible to design rehabilitation training protocols to improve reading performance. The relationship between the reading speed across character sizes curve and visual function were examined to establish which visual factors influence the characteristics of the reading speed curve.
Pattern Masking Experiments Reveal ON and OFF Pathway Function
Authors: Bowen Richard W.
Published: February 2023

It is well know in visual neurophysiology that units of the retinocortical pathway are selective for luminance and contrast polarity. The so-called ON and OFF pathways are comprised of cells responding either to increments in luminance or contrast (ON pathway) or decrements (OFF pathway)1. Although many psychophysical studies have manipulated stimulus polarity, there are relatively few papers that convincingly link polarity manipulation to selective activation of ON or OFF mechanisms. For example, there have been many demonstrations of threshold asymmetries, which typically show greater sensitivity to luminance decrements than increments2. But such a polarity asymmetry could occur in a generic visual pathway that had a nonlinear luminance or contrast response, and this result does not demand the existence of ON and OFF pathways in humans. More convincing evidence for selective ON and OFF pathway activation comes from studies of aftereffects of temporal sawtooth adaptation3, in which viewing of one polarity of sawtooth (either rapid on or rapid off) raises threshold for test stimuli of the same polarity more than for test stimuli of opposite polarity. This asymmetry suggests that polarity-sensitive visual mechanisms can be differentially adapted, and the result is consistent with a two-pathway ON-OFF model of luminance or contrast processing in the human visual system.
Astigmatic Refraction Measurement With Eccentric Photorefraction — Some Theoretical Considerations —
Authors: Kusel Reinhard , Oechsner Ulrich
Published: February 2023

Eccentric photorefraction is an objective refraction technique which allows determination of refractive errors in human eyes from a distance of typically 0.5 — 5 m. It is used as an early diagnostic test in infants and small children (Bobier and Braddick [1], Kaakinen, Kaseva and Teir [2], Angi and Cocchiglia [3], Hamer et al. [4]) as well as in animal models of myopia (Schaeffel and Howland [5]).
Tolerance to Defocus at Low Spatial Frequencies: Effect of Luminance
Authors: Coletta Nancy J. , Maggisano Lori A.
Published: February 2023

The effects of optical defocus on spatial contrast sensitivity are frequency dependent: defocus is detrimental to the visibility of high spatial frequencies, while low spatial frequency sensitivity is relatively less affected by the eye’s refractive state (Charman, 1979; Green and Campbell, 1965; Tucker, Charman and Ward, 1986). One would expect that vision at low luminance levels would be relatively unaffected by defocus, because the range of visible patterns is limited to lower spatial frequencies. However, Bedell (1986) reported that the contrast sensitivity loss produced by +1.25 D of defocus extended to lower spatial frequencies when the luminance was reduced. Similarly, the eye’s optical quality has a greater effect on low frequency sensitivity at low luminance than at high luminance levels (Coletta and Sharma, 1994). Experiments with acuity targets of fixed contrast also imply a decrease in tolerance to defocus at low luminance (Simpson, et al., 1986). Tucker and Charman (1986) measured acuity for gratings of 80% modulation as a function of focus and found that the through-focus acuity functions became narrower at mesopic luminance, even though the acuity limits shifted to lower spatial frequencies.
Performance on the Three-Point Vernier Acuity Test as a Function of Age: Study Extended to Encompass the Age-Range, 10-94 Years
Authors: Kim Eunice , Enoch Jay M. , Fang Michelle , Kono Momoyo , Lakshminarayanan Vasudevan , Srinivasan Ranjani
Published: February 2023

In recent years, this laboratory has published a series of papers on a simple three point vernier acuity (alignment) test having rather unique properties and offering particular promise as a clinical test. Included in this set of properties is essential independence of responses to this test from effects of aging. And if the test is conducted at super-threshold settings and the test points can be identified as separate from each other; background and test luminance levels, contrast, veiling glare, test spot size, and image degradation (even extreme) do not meaningfully alter outcomes. Because of the potential value of this test as a reference or “gold” standard, and for purposes such as assessment of vision through dense media disorders, we seek to develop further the data base supporting this test. Here, we extend the age range sampled from 20-94 (previous study) to include ages 10-19 years. Not surprisingly, the three point vernier acuity test was shown not to vary significantly with aging within this age span as well.
Neural Network-Assisted Interpretation of Digitized MTI Photoscreening Images
Authors: Miller Joseph M. , Schwiegerling Jim , Hall Heidi , Harvey Erin M. , Dobson Velma , Mansueto Lisa A.
Published: February 2023

The MTI Photoscreener is a commercially-available device that performs eccentric photo refraction in the vertical and horizontal meridia. These two separate images are both recorded on a single piece of Polaroid film. The image is recorded at a magnification of 1× and so direct measurement of pupil size is possible.
An Actinic Mechanism for Cataractogenesis
Authors: Kwok L. Stephen , Coroneo Minas T.
Published: February 2023

The crystalline lens is a critical component of the human ocular media. Loss of transparency of the lens substance can lead to significant loss of vision with concomitant impairment of lifestyle and mobility.
Spin current and spin Hall effects
Authors: Li You-Quan
Published: February 2023

In terms of SU(2) Yang-Mills field formulism, we give a nature definition of spin current for the systems with Rashba or Dresselhaus spin-orbit couplings etc., and we obtain a covariant form of continuity equations for the corresponding spin current [1]. The traditional Kubo formula is generalized to describe the linear response with respect to non-Abelian fields. We find that the covariant form we proposed plays an essential role in guaranteeing the consistency of SU(2) Kubo formula [2]. We also derive the classical counterpart of quantum mechanical covariant “continuity-like” equation for the spin current, and present an intuitive picture for elucidating the non-conservation of the spin current [3]. We discuss the spin-relaxation time for two-dimensional systems with a hierarchy of spin-orbit couplings, and found that the spin-relaxation time can be infinite if the coupling strengths certain condition which correspond to the vanishing Yang-Mills “magnetic” field [4].
Dynamical decoupling induced renormalization of the non-Markovian dynamics
Authors: Chen Pochung
Published: February 2023

We develop a framework to study the dynamics of a system under dynamical decoupling. We investigate several scenarios and assess the efficiency. We find that the efficiency critically depends on the spectral density of the bath and the envelope of the decoupling pulses.
Production of Entangled Images With a 4-Wave Mixer
Authors: Boyer V. , Marino A. M. , Pooser R. C. , Lett P. D.
Published: February 2023

We show that non-degenerate 4-wave mixing in an atomic vapor can produce highly multimode twin beams. When seeded, the process generates arbitrarily-shaped bright twin beams whose intensities are quantum-correlated in time and in space. When operating with a vacuum input, it generates multimode continuous-variable entangled twin beams.
Controllable inter-qubit couplings in superconductor quantum circuits
Authors: Liu Yu-xi , Nori Franco
Published: February 2023

After a brief review on superconducting qubits, we overview our recent studies on controllable couplings in superconducting flux qubits via a variable frequency (ac) magnetic flux. In particular: (i) we describe how to use a variable frequency magnetic flux to control the coupling between two inductively coupled flux qubits, (ii) Based on this approach, using a variable frequency controlled coupling, we present a proposal on how to achieve scalable quantum computing circuits with flux qubits. We also explain why superconducting qubits can be coupled and addressed as trapped ions, as well as describe how to utilize dressed states to couple and decouple qubits and the data bus.
Nanoparticles Doped Liquid Crystal Filled Photonic Bandgap Fibers
Authors: Scolari Lara , Gauza Sebastian , Xianyu Haiqing , Zhai Lei , Eskildsen Lars , Alkeskjold Thomas Tanggaard , Wu Shin-Tson , Bjarklev Anders
Published: February 2023

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum to the one achieved with undoped liquid crystals. New interesting features such as frequency dependent behavior and a transmission spectrum with tunable attenuation on the short wavelength side of the bandgap suggest a potential application of this device as a tunable all-in-fiber gain equalization filter. The tunability of the device is demonstrated by changing the temperature of the liquid crystal and by varying both the amplitude and the frequency of the applied external electric field.
Tailoring the Nonlinear Response of Hollow-core Photonic Bandgap Fibres
Authors: Welch Matthew , Correa Rodrigo Amezcua , Gérôme Frédéric , Renshaw Steve , Knight Jonathan
Published: February 2023

We have fabricated 7-cell and 3-cell core hollow-core photonic bandgap fibres with core sizes ranging from ~ 16.7 µm to 6.5 µm. A numerical study of the nonlinear coefficient of fibres with different core sizes is carried out. We show that the nonlinearity is more effectively increased by a 3-cell core design than by reducing the size of a seven-cell core.