bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum Theory of Vibrational Relaxation in Liquids
Authors: Kenkre V. M.
Published: February 2023

We present a theory of vibrational relaxation of polyatomic molecules in polyatomic solvents, which is also applicable to solid solutions, with Fermi's Golden Rule as the point of departure. We avoid rotating wave or random phase approximations, and treat both the internal degrees of freedom of the relaxing molecule and the bath degrees of freedom in a fully quantum mechanical manner. The results allow one to go beyond earlier analyses which treated only cascade processes and to consider all participating bosons. We construct the theory in a manner which facilitates the use of recent developments in the analysis of instantaneous normal modes of liquids. We address the problem of the inverted temperature dependence of the relaxation rate observed recently by Tokmakoff, Sauter and Fayer (J. Chem. Phys. 100, 9035 (1994)) and provide three different possible explanations of the phenomenon. The first is based on the temperature dependence of the density of states of the instantaneous normal modes as suggested by the authors of the experimental paper. The second stems from an energy mismatch mechanism which gives rise to dressing effects. The third arises naturally from the representation of the dynamics of the liquid in terms of anharmonic oscillators.
Infrared Spectroscopy using Difference Frequency Generation in AgGaS2: Propargyl Radical
Authors: Eckhoff W. C. , Yuan L. , Billera C. , Curl R. F. , Miller C E.
Published: February 2023

The propargyl radical (HCCCH2) is of interest as a possible precursor in benzene and soot formation in flames and as one of the simplest conjugated organic free radicals. Because of its importance, several spectroscopic investigations of this species have recently been carried out.1-4 In order to learn more about its structure and potential surface, we have begun an investigation of the high resolution infrared spectra of the partially deuterated form, DCCCH2 in the region of the CD stretching fundamental. In this work an infrared kinetic spectroscopy apparatus5 based on difference frequency generation in the nonlinear material AgGaS2 was employed.
Energy flow in molecular solids
Authors: Dlott Dana D.
Published: February 2023

The heating and cooling of a condensed phase molecule is of considerable interest in many areas of chemistry. Owing to the short distance scale (nanometers) and time scale (picoseconds) of these processes, the conventional concepts of thermal conduction do not apply. Instead the more complicated approach of molecular mechanical energy transfer needs to be considered.
Raman Echo Studies of Vibrational Dephasing
Authors: Berg Mark , Bout David Vanden
Published: February 2023

In the condensed phase, interaction with the environment causes vibrational dephasirtg and broadening of isotropic Raman lines. However, measurements of the Raman line width provide only a limited probe of these interactions. They cannot directly determine the lifetime of the interactions. In different language, the line width could be due to either inhomogeneous broadening (long lifetimes) or homogeneous broadening (short lifetimes).
Three-Dimensional Motion Analysis by Direct Matching
Authors: Huang T.S.
Published: February 2023

Determining the relative motion between an observer and his environment is a major problem in computer vision. Its applications include mobile robot navigation and monitoring dynamic industrial processes. Although much work has been done recently in motion estimation, the problem is far from being solved. It is the purpose of this brief paper to outline an approach to motion estimation and to point out some of the difficult issues.
A Filtering Approach for the Estimation of 2-D Motion Parameters of a Planar Body
Authors: Broida Ted J.
Published: February 2023

A significant amount of work has been devoted to the estimation of the motion parameters of a rigid body based on a sequence of images. As discussed in [1], the problem of noisy point correspondences (match points) in the estimation of 3-D motion from 2-D images is as yet unresolved. In [2], a linear filtering approach is introduced for the case of a longer sequence of noisy images of a rigid body whose motion is restricted to a plane. In this summary, a nonlinear filtering approach is presented. By using a sequence of 10 to 30 images and one or more match points, an Iterated Extended Kalman (IEKF) Filter can be used to estimate motion parameters in the presence of significant measurement noise. The ultimate goal of this approach is the estimation of 3-D motion parameters from a sequence of noisy 2-D images. The feasibility of the approach is demonstrated here for the case of a noisy 1-D image of a 2-D rigid body.
Motion Estimation and Object Recovery with Time-Sequentially Sampled Imagery*
Authors: Allebach J. P. , Chen D. S. , Koskol J. B.
Published: February 2023

Algorithms for estimating the motion of a moving object from digital imagery acquired in real time generally rely on two important assumptions: 1) the field of view is sampled frame-instantaneously, i.e. a record of the radiation integrated over a time interval that is short compared to the frame interval is stored at the focal plane, and this frozen image is read out serially during the interval between frames; and 2) there is relatively little change in the image between consecutive frames. With many digital imaging systems, the field of view is sampled time-sequentially during the entire interval between frames; and the radiation sensed at the focal plane changes continuously during this time. Typically, the field of view is sampled in a lexicographic (LEX) or 2:1 line-interlaced (2:1-LI) fashion. These patterns are illustrated in Table 1 which shows the order in which a 4 × 4 array of points would be sampled. With both these patterns, consecutive samples are clustered spatially. Table 1 also shows three dot-interlaced sampling patterns which disperse consecutive samples over the entire field of view. The 2:1 dot-interlaced (2:1-DI) and bit-reversed dot-interlaced (BRV-DI) patterns have been considered for bandwidth compression in video systems. The congruential dot-interlaced (CGR-DI) pattern has been shown to be optimal for sampling bandlimited signals [1],[2]. It also simplifies certain signal processing operations [3]. This particular pattern generates a 5 × 4 array of samples.
Machine Perception of Partially Obscured Planar Shapes
Authors: Singer P.F , Chellappa R.
Published: February 2023

The perception of shape is an important factor in the recognition of an object by the human visual system. This alone justifies the investigation and use of shape descriptors for machine recognition of objects. Shape also has the desirable qualities of being invariant to lighting conditions, changes in sensor parameters or variations in the associated electronics. Some sets of shape descriptors (eg. Fourier descriptors and moment invariants) have other restrictions on their use such as requiring complete and perfect knowledge of the shape boundary. Recent results reported by [1] used the Fourier Mellin transform in the recognition of aircraft with missing pieces. This technique produces inconsistent feature estimates and the reported experiment used an inadequate number of test samples.
Texture Segmentation Using Gaussian Markov Random Field Models
Authors: Chatterjee Shankar , Chellappa Rama
Published: February 2023

Segmentation of imagery data has received much attention because of its potential application in several disciplines, e.g., medicine, remote-sensing, robot vision etc.. The image segmentation problem can be specified in the following way: let A be the index set for the pixel values for the whole image; we assume that there exists a partition on A, A = A1 ⋃ A2 ⋃…⋃ Aq such that Ai ≠ ϕ and Ai ∩ Aj = ϕ ∀ i ≠ j, where each Ai is homogeneous in some sense. Thus the problem is to find A1, A2,...,Aq. The segmentation problem has been approached using both structural and statistical procedures.
Computing Polygonal Masks in Pipeline Architectures for Automated Visual Inspection Applications
Authors: Sanz Jorge L. C. , Dinstein Its’hak , Petkovic Dragutin
Published: February 2023

In image analysis and computer graphics there are many different application problems which require the computation (and drawing) of binary and multi-tone (colored) digital polygonal masks. It is necessary to clarify that ’binary digital polygonal mask’ should be understood as to mean a (0-1) image where the set of pixels with value 1 describe a digital planar polygon of arbitrary number of vertices. In other words, if P denotes a digital planar polygon, we would like to obtain an image Is such that More generally, we may be given more than one polygon in the same image. In this case, we would like to assign different codes to each polygon in the image. In other words, if Q1, Q2,…,Qd are the given polygons (whose interiors are assumed disjoint), we wish to obtain an image Im such that for all k=1,…,d where c’s, d’s are different codes, and

Q
˙

k

denotes the interior of the polygon Q
k
.
Hierarchical Feature-Based Object Identification
Authors: Casasent David , Lee Cheatham R.
Published: February 2023

A feature space processor for multiclass distortion-invariant pattern recognition is detailed in Section 2. A moment feature vector space is considered. Test data [1, 2] on a robotic database are summarized in Section 3. Results on a ship database, using real input imagery with references from models is presented with attention to preprocessing, distortion parameter estimation, and class identification are advanced in Section 4.
Design of a Knowledge Based Computer Vision System for Industrial Applications
Authors: Wieland Alexis P.
Published: February 2023

A summary of the design of a knowledge and model based, goal driven, heterarchical image understanding system currently being developed at URI.
A High-Speed Analog Two-Dimensional Gaussian Image Convolver*
Authors: Sage J. P. , Lattes A.
Published: February 2023

This paper describes a new charge-coupled device (CCD) focal-plane image-processing technique that can carry out the convolution of an image with two-dimensional Gaussian kernel functions. Such Gaussian convolution operations are the computationally intensive steps in the difference-of-Gaussian procedure employed in artificial intelligence algorithms for the detection and location of the edges of objects in an image. Devices using our technique can produce convolutions for a wide range of Gaussian widths over an arbitrarily large field of view in a time less than that required to detect the original image.
CCD Focal Plane Convolver (Smart Eyeball)
Authors: Beaudet Paul R.
Published: February 2023

The CCD focal plane convolver is a smart optical sensor capable of off-loading the massive number of multiplies and additions required for extracting many of the spatial primatives required in optical pattern recognition; most spatial and temperal convolutions can be extracted at extremely rapid rates and in parallel.
Interferometry for 3-D Sensing
Authors: Wyant James C.
Published: February 2023

Interferometric techniques can be used for performing a wide range of measurements. Measurements can be made of absolute shapes, changes in shapes, or vibrational modes. While the normal sensitivity of interferometry using visible light is fractions of micrometers, reduced sensitivity can be obtained by either using a longer wavelength light source or special interferometric techniques.
Rotation and Scale Invariant Recognition Using Optimum Feature Extraction
Authors: Stark Henry , Wu Ron
Published: February 2023

One would expect a machine vision system to recognize, say, a hammer regardless of its orientation (rotation) and size (scale). While rotation and scale invariant recognition is trivial for humans, it turns out to be a surprisingly sophisticated task for machines.
Correlation Filters for Distortion-Invariance and Discrimination
Authors: Casasent David , Mahalanobis Abhijit
Published: February 2023

Correlators are powerful shift-invariant object recognition systems that perform well in noise. However, they are quite sensitive to distortions between the input and reference object. Synthetic discriminant functions (SDFs) [1] accommodate intra-class distortions and provide interclass discrimination. In Section 2, we review these projection SDFs and note that they restrict only the peak point in the correlation plane. In Section 3, new correlation SDFs [2] are described. They control both the peak and sidelobe response and thus exhibit superior performance. Initial test data on these SDFs are presented in Section 4.
The Role of Optics in Machine Vision
Authors: Horn Berthold K.P.
Published: February 2023

The task of a machine vision system is to produce a description of a three dimensional world suited for some application. The description is based on one or more images. Images are two dimensional distributions of brightness generated by an imaging device. The problem can be viewed as one of inversion: If we understand the projection process which creates images from the three dimensional world, we can hope to reverse this process to recover information about the world.
A Model for the Extraction of Image Flow1
Authors: Heeger David J.
Published: February 2023

A model is presented, consonant with current views regarding the neurophysiology and psychophysics of motion perception, that combines the outputs of a set of motion-sensitive spatiotemporal filters to estimate the velocity of a moving texture — without first computing component (or normal) velocity. A parallel implementation of the model encodes velocity as the peak in a distribution of velocity-sensitive units that behave much like cells of the middle temporal (MT) area of the primate brain.
Real-Time Optical Multiple-Object Recognition and Tracking Demonstration: A Friendly "Challenge" to the Digital Field
Authors: Chao Tien-Hsin , Liu Hua-Kuang
Published: February 2023

We demonstrated by video display that a number of different objects making independent motions can simultaneously be recognized and tracked via coherent optical techniques.
Finding Object Boundaries Using Guided Gradient Ascent1
Authors: Leclerc Yvan , Fua Pascal
Published: February 2023

In real world images, physical event discontinuities cannot be detected solely by their local statistical signature in the image due to the presence of noise and various photometric anomalies. Therefore all methods for finding discontinuities that use purely local statistical criteria are bound to make mistakes and miss some of the weaker parts of edges.
An efficient image representation for multiscale analysis
Authors: Mallat Stephane
Published: February 2023

In order to analyze an image, one needs to separate the signal changes occurring at different scales because they often corresponds to distinct physical structures. Since Rosenfeld’s6 work, people have tried to solve this problem by analyzing the image at several resolutions. They reproduce the image at different scales, process each of these and eventually infer some interesting information by comparing the outputs. In such an approach one increases the volume of data. This is computationally and conceptually inefficient. Indeed, after processing an image at a certain scale we are only concerned with the supplement of information available at a bigger scale and we do not need to reprocess the redundant details. With a new mathematical model, we will show how to extract this information and isolate the signal changes occurring at the different scales. It will enable us to build a convenient and efficient image representation for multiscale analysis.
Components of an Intelligent 3-D Sensor System
Authors: Jalkio Jeffrey A. , Bolkcom John E. , Kim Richard C. , Bocchi Curt J. , Case Steven K.
Published: February 2023

Application specific 3-D sensor design is discussed. The problems encountered in metrology and vehicle navigation domains are examined. Accuracy limitations in both areas are considered.
Fiber Based Chirped Frequency Interferometric Distance Sensor
Authors: Eichen Elliot , Silletti A. , Carisen W.J. , Melman Paul , Cook K.
Published: February 2023

The optical path difference (OPD) in a classical heterodyne interferometer is derived from the phase of a sinusoidally oscillating signal[l]. Thus surfaces with discontinuities > A cannot be measured due to ambiguities of 2% in phase. Similarly, target distances > A cannot be measured except by counting fringes under translation from a known reference point. If the optical beam is interrupted the reference point can be lost, making heterodyne interferometers difficult to use for robotic applications.
Why Image Understanding?
Authors: Pentland Alex P.
Published: February 2023

Image Understanding is rapidly becoming one of the most important components of image processing research; it is already the most important in terms of basic research dollars. Its goal is to transcend the limitations of conventional pattern recognition techniques by using additional information about the image formation process. We provide a brief overview and history of the field.
Scintillation effects on images by adaptive synthetic apertures in the atmosphere
Authors: Consortini A. , Nourrit V.
Published: February 2023

The effect of intensity fluctuations on images by synthetic apertures is investigated in the case when partial or total phase correction is achieved. A simple adaptive optics imaging system is constituted by a two hole aperture, illuminated by the field after the adaptive correction of the phase. The problem is therefore reduced to investigating Young’s interference pattern of two holes in a screen illuminated by a field with amplitude and phase fluctuations. In the case of perfect phase correction, of course, there are no phase fluctuations.
Applications of Shack-Hartman wavefront sensing and adaptive optics for in place laser gain media measurements and for horizontal path optical communications
Authors: Levine B. Martin , Wirth Allan , Landers Franklin , Martinsen Elizabeth , Jankevics Andrew , Toledo-Quinones Manuel , Bruno Theresa , Zielinski Robert
Published: February 2023

The Shack-Hartmann wavefront sensor is a miniaturized version of the classical Hartmann mask extended by using a two-dimensional array of lenslets that is optically conjugate to the wavefront surface under test. The sensitivity and dynamic range of the wavefront measurement is controlled by the combination of reimaging optics and the diameter and focal length of the lenslet array. This allows an adjustment of the gradient measurement sensitivity . As the beam size is reduced in reimaging the test surface, the angular spread of the beam is magnified. This magnification increases the size of the gradients or tilts of the ray bundles from micro-radians to milliradians for typical testing configurations. Measurements of such large angles are not so prone to error due to mechanical and thermal instabilities in the sensor equipment as are interferometric sensors where dimensional stability must always be measured in parts of a micron. It is this flexibility that makes it possible for the same sensor system to measure with very high accuracy the wavefront produced by a Hubble Space Telescope simulator and, with a change of lens array, the shape of f/0.7 paraboloids.
Adaptive Correction of Laser Beam Aberration On Atmospheric Paths
Authors: Lukin Vladimir P. , Fortes Boris V.
Published: February 2023

We consider here adaptive (phase conjugation) optical system for the correction of non-linear distortion with the independent reference beam. We can use either cooperative beacon from independent source, either glint on the target surface, either natural guide star, or artificial guide star, formed using atmospheric scattering of the light. First of all we will consider "exact" phase conjugation and "phase unwrapping" technique. Phase conjugation algorithm allows significantly decrease the atmospheric aberrations due to the thermal blooming and the atmospheric turbulence both for vertical and horizontal paths.
Liquid Crystal Phase Modulators For Time Phase Distortion Simulations
Authors: Gonglewski J. , Kudryashov A. , Browne S. , Highland R.
Published: February 2023

Nematic liquid crystals have been used as phase retarders for adaptive optics for more than 10 years. Of the available options, liquid crystals phase modulators (LCPMs) have the advantages of low cost, reliability, compactness, low power, ease of controllability, a transmissive nature, and simple aperture scalability. A number of groups have investigated the use of LCPMs for adaptive wavefront control and demonstrated preliminary results.1-6 The current limitation for using these devices in atmospheric adaptive systems is their relatively slow response times. In this paper we present the results of turbulence simulation with a 127 element LCPM. The turbulence is statistically appropriate for the atmosphere in both temporal and spatial correlation, except for the low spatial and temporal frequency limitations of the LCPM. We address the limitations and potentialities of such modulators.
Focal ERG Measures of Temporal Modulation Sensitivity
Authors: Seiple William , Siegel Irwin , Carr Ronald
Published: February 2023

In this study we applied the powerful stimulus control inherent in
psychophysical methods to electroretinographic study of the modulation
sensitivities (deLange curves) of the mid-and outer-retinal layers in
the macular region. Focal ERG (FERG) thresholds were determined both
by signal averaging and by using lock-in amplifier retrieval of
responses in real-time. The aim of this study was to partition out the
retinal contribution to the deLange curve (the FERG data) and compare
the results with the similarly derived psychophysical results.
Hyperacuity: Assessing visual function behind ocular opacities
Authors: Williams R.A. , Enoch J.M.
Published: February 2023

The term hyperacuity refers to visual tasks for which the question asked of the observer is, for example, "Where is the upper line in relation to the bottom one?", as in vernier acuity and stereoacuity. Resolution tasks ask a different question; for example, "Do you see one or two lines?" It is not uncommon in hyperacuity tasks that one can judge relative spatial position to an accuracy of 3 seconds of arc, a visual angle 10 times smaller than the center-to-center spacing of individual foveal cones. This is the basis for the term "hyper"-acuity (Westheimer, 1979).
Stiles-Crawford Functions are not Broader After One Week of Total Light Exclusion
Authors: Hamer R.D. , Yasuma T. , Lakshminarayanan V. , Enoch J.M. , Birch D.G. , Birch E.E.
Published: February 2023

Previously, it has been reported (Enoch, Birch & Birch, 1979; Enoch & Birch, 1981) that complete occlusion of an eye for 7 days will result in a broadening of the Stiles-Crawford (S-C) function. It was suggested that this broadening reflected a dispersal of the photoreceptors, which normally tend to have their long axes aligned pointing towards the center of the exit pupil (Enoch & Hope, 1972). This result, along with the observation that the peak of the S-C function could be selectively shifted by wearing a contact lens with an off-center artificial pupil, provided support to the hypothesis that the normal mechanism of alignment of the receptors is a positive phototropism.
The Clinical Measurement of Vernier Acuity
Authors: Fendick M.
Published: February 2023

The variability normal human subjects exhibit in repeatedly adjusting the position of one spatially discrete visual stimulus so as to place it in apparently perfect horizontal or vertical alignment with another is referred to as their vernier acuity. The magnitude of this variability corresponds to a visual angle of about one-fourth that subtended by the eye’s smallest photoreceptors. The mean error of a subject’s vernier alignment settings reflects any directional bias of his judgements of relative stimulus location and this may vary independently of one’s vernier acuity (see Baker & Bryan, 1912; Guild, 1930; and Fendick, 1984). Vernier acuity is a member of the class of human visual capabilities referred to as the hyperacuities (see Westheimer, 1981 for a review). Like other hyperacuities, it is remarkably robust to various stimulus parameters, including luminance (Baker, 1949 and Leibowitz, 1955), duration (Westheimer & McKee, 1977), and blur (Stigmar, 1971). This, as well the obvious fact that such fine spatial discrimination must necessarily require post-receptor neural processing of one form or another makes vernier acuity a superb candidate for clinically assessing spatial visual function. Although normal subjects viewing nearly abutting stimulus elements demonstrate directional biases that are small relative to their vernier acuity, the same is not true for patients exhibiting clinical disorders in which the retina is stretched or otherwise distorted (Fendick, unpublished data). Alignment biases in such cases are consistent with perceptual spatial distortions evidenced by the Amsler Grid test.
Differential Growth in Acuity for Pattern Reversal and Pattern Onset-Offset Targets
Authors: Orel-Bixler Deborah A. , Norcia A.M. , Smith-Kettlewell
Published: February 2023

The Visual Evoked Potential (VEP) has been used by a number of investigators for non-invasive assessment of the development of visual acuity in human infants. In all these studies, visual acuity develops to near adult levels during the first year of life. Close inspection of these growth curves reveals an interesting difference in the apparent rate of acuity development during the first year. Data from studies which have used the pattern onset/offset mode of stimulus presentation (Marg et. al., 1976; de Vries-Khoe and Spekreijse, 1982) indicate that acuity develops rapidly at a rate of 0.5 octaves/month from an initial level of 1 to 2 c/deg. Our studies using the contrast reversal presentation mode (Norcia and Tyler, in press) indicate a growth rate of only 0.25 octaves/month, but from an initially higher level -- around 4 to 5 c/deg. We thus decided to test the same infants on the two different acuity tasks. A difference between the two presentation modes would have important implications for the choice of the best presentation mode for use in clinical testing, as well as for theories of acuity development.
The Electroretinogram in Ischemic Retinopathies
Authors: Johnson Mary A. , Finkelstein Daniel
Published: February 2023

Retinal or iris neovascularization (NV) is a complication of diabetic retinopathy, branch and central vein occlusion, Eale’s disease, sickle cell retinopathy, and other retinal-vascular disorders which have as their common element extensive retinal capillary non-perfusion. This vascular proliferation is thought to occur as a response to the reduced retinal perfusion. The new vessels, however, do not grow normally and because of this, place the patient at risk for severe visual loss due to vitreous hemmorhage and/or fractional retinal detachment, or in the case of irisneovascularization (rubeosis), acute (closed-angle) glaucoma.
Pattern Visual Evoked Potentials Recorded Under Chloral Hydrate Sedation
Authors: Eriksen K. Jeffrey , Wright Kenneth W. , Shors Tracey J. , Ary James P.
Published: February 2023

The accurate assessment of visual function in infants and preverbal children is crucial to the appropriate management of pediatric eye disorders. Decisions regarding pediatric cataract surgery, corneal surgery, the dispensing of glasses, and patching therapy are dependent upon knowledge of visual function and the presence of amblyopia. Unfortunately, there are only a few quantitative methods available to test infant vision and these have not been accepted for routine clinical use [1,2]. The two most widely used methods are preferential looking [3,4] and the pattern visual evoked potential (P-VEP) [5,6], Fixation preference testing has also been used to detect amblyopia in preverbal children, but this test does not quantitate visual function [7,8]. A common shortcoming of these tests is the requirement for patient cooperation.
Disability Glare in Radial Keratotomy
Authors: Meade Diana L. , Applegate Raymond A. , Trick. O.D. Linda R. , M.D. Jack Hartstein.
Published: February 2023

Radial Keratotomy (RK) is a surgical procedure designed to correct moderate amounts of myopia. Currently the procedure consists of eight peripheral incisions of up to 90% of the corneal thickness leaving a 3 - 4 mm central clear zone centered on the optic axis. The procedure is designed to weaken the corneal structure inducing an increase in the corneal radius of curvature, thereby reducing corneal dioptric power. After the surgery patients often complain of increased sensitivity to glare; this subjective complaint1 is measurable2 and has resulted in changes in behavior such as altered driving patterns and refusing surgery in the second eye3.
Glare Effects in Normal and Low Vision1
Authors: Rubin Gary S. , Legge Gordon E. , Schleske Mary M.
Published: February 2023

Glare is an important problem for many people with low vision. A glare source located some distance from an object of interest can interfere with the recognition of that object. One likely cause of glare is abnormal light scatter in eyes with cloudy ocular media (due to cataract, corneal opacities, vitreous debris, etc.). Another possible cause of glare may be neural in origin. There is some evidence2 for greater lateral masking in peripheral vision than in central vision. Therefore, individuals with central field loss who must use their peripheral vision to read or recognize objects may be bothered by glare, even though their ocular media are clear. We are investigating glare in low-vision subjects with clear or cloudy media, and different forms of field loss.
An Infrared Photoretinoscope
Authors: Howland Howard C. , Schaeffel Frank , Farkas Leslie
Published: February 2023

Much attention has been paid to methods tor measuring the plane of focus of the eye with little or no cooperation of the subject (1,2). We present here a simple arrangement to do this using infrared light emitting diodes (LEDs). Long wavelength light (approx. 900 nm) does not induce a pupil response, thereby allowing measurement at large pupil sizes and increasing the sensitivity of the retinoscopy. The method is a modification of one popularized by Kaakinen (1). By contrast, however, in our method a) we use infra-red light rather than visible light and b) the light source is positioned at different distances (eccentricities) from the optical axis of the camera while the fundus reflex is observed. Whether or not a reflex can be detected depends on the defocus of the eye relative to the camera, D, the pupil size, P, the excentricity, E, of the light source from the optical axis, and the camera to subject distance, A. In a theoretical treatment of photoretinoscopy by Howland (3,4) the defocus of the eye relative to the camera is shown to be given by the equation: (1) where DF is the Dark Fraction or ratio of the portion of the diameter of the pupil which is dark to that which is illuminated by the fundus reflex.
Two Mechanisms Revealed by Sweep VEP Contrast Functions in Infants
Authors: Tyler Christopher W. , Norcia Anthony M. , Hamer Russell D.
Published: February 2023

The characteristics of the VEP response function to contrast were determined for a group of 5-6 month old infants. Previous measurements of VEP contrast response functions in infants (Norcia, Tyler and Allen, 1986) have shown that the contrast functions were not always monotonic, but often had two distinct limbs at different contrast levels. These limbs are seen in adult contrast response functions (Tyler and Apkarian, 1985), and may correspond to the responses of two separate mechanisms contributing to the VEP response.
Objective Testing of Local Retinal Function
Authors: Sutter Erich E.
Published: February 2023

The human retina with its vasculature and supporting tissues shows variations in anatomy and physiology across its surface. These variations determine the local susceptibility of the retina to different disease processes. In fact, the distribution of retinal defects can be a characteristic of the disease at hand and is thus important for diagnosis. In addition, the growing and shrinking of the affected areas is often the main indicator in monitoring the disease process and evaluating treatment.
Do white-light interferometers bypass the eye's optics? Clinical implications of decentering the optical beam in the pupil
Authors: Thibos Larry , Bradley Arthur , Still David , Henderson Patricia
Published: February 2023

Interferometric methods are valuable for two main reasons in the determination of actual or potential visual acuity in patients with a variety of pathologies. First, light enters the eye as two closely spaced bundles of rays which can be maneuvered to avoid opacities of the ocular media. Second, the test pattern consists of interference fringes formed directly on the retina without being focused by the eye's natural optical system. Consequently, the image quality produced by such an instrument is largely unaffected by ocular errors of focus, such as astigmatism, coma, spherical aberration and longitudinal chromatic aberration (Westheimer, 1960).
Analyses of Flash-on-Flash Threshold Elevations
Authors: Massof Robert W. , Marcus Sergiu
Published: February 2023

Greenstein, Hood and their colleagues have made extensive use of the ”flash-on-flash” technique to study mechanisms of psychophysical threshold elevations in various retinal diseases.1-2 In the flash-on-flash experiment, a flashed test stimulus of intensity ΔI is superposed on a coincidently flashed, but longer duration background stimulus of intensity I. Test flash increment thresholds as a function of flashed background intensity follow a saturating function rather than Weber’s law, the usual function obtained for increment thresholds on steady backgrounds.
Visual fields of infants: a new perimetry
Authors: Mayer DL , Cummings MF , Fulton AB
Published: February 2023

The description of visual-Fields is important in the diagnosis and management of ophthalmologic and neurologic disorders of adults. Ordinarily, effective assessment of visual fields of children using established perimetric techniques is not possible until at least age 8 years. The behavioral repetoire of infants and young children thus has required invention of new techniques. Recently we reported successful assessment of visual fields of young children using an LED perimeter and an 8-alternative forced-choice procedure (1). Here we describe a LED perimetric method to assess 6- to 7-month-old infants. A combination of these techniques has enabled assessment of infants with neuro-ophthalmologic conditions known to result in visual field defects.
Early Glaucoma Detection with Pattern Discrimination Perimetry
Authors: Drum Bruce , Breton Michael , Massof Robert , O'Leary David , Severn Matthew
Published: February 2023

The task in conventional perimetry is to detect an incremental spot of light on a uniform background. The recent work of Quigley, et al.1 indicates that conventional perimetry can be insensitive to large amounts of optic nerve damage in glaucoma. This lack of sensitivity is not surprising, considering that individual ganglion cells can respond to light intensities close to normal psychophysical thresholds.2,3 A single functioning ganglion cell receptive field at the test stimulus position might therefore yield a nearly normal sensitivity measurement, even though as many as ten receptive field centers would normally cover that position.4
Noninvasive Assessment of Retinal Macular Capillary Blood Flow Regulation
Authors: Riva Charles E. , Zuckerman Ralph , Petrig Benno L. , Grunwald Juan E.
Published: February 2023

Quantitative determination of retinal blood flow and its regulation is fundamental to an understanding of the pathophysiology of the retinal vascular system and to an objective evaluation of the effect of treatment. Of particular importance is the quantification of blood flow in the capillaries, where the exchange of nutrients and waste products takes place. For example, impairment of this exchange is believed to play an important role in the development of diabetic retinopathy, a disease which often results in severe visual loss.
Towards Computer-Assisted Clinical Retinal Laser Doppler Velocimetry
Authors: Petrig Benno L. , Riva Charles E.
Published: February 2023

The retina is among the few tissues in the human body where blood circulation can be observed directly and noninvasively. This has facilitated a detailed description of the morphological changes of the retinal vasculature caused by many ocular and systemic diseases. Despite the accessibility of the retinal vasculature and the obvious importance of blood flow, quantitative data on the retinal hemodynamics in the normal and diseased retina is not available to the clinician. Assessments of "normal" or "low" flow based on fluorescein angiography remain qualitative and the fluorescein dye dilution technique has had limited success in providing a quantitative measure of retinal blood flow.
Psychophysical Tests of Dopamine Anomalies in the Retina
Authors: Enoch Jay M. , Savage Gary L. , Lakshminarayanan Vasudevan
Published: February 2023

In recent years there has been great interest in the analysis of neurotransmitter substances and their role in vision and other central nervous system processes. Much evidence has accumulated implicating dopamine as a neurotransmiter in the retina. It is present in certain amacrine, interamacrine and interplexitorm cells (1-5, 8-10). As our knowledge about the role of dopamine in visual processing is limited, a key question to ask is, "are there functional visual effects due to anomalies of the dopamine system in the retina?".
Temporal Chromatic Sensitivity in Glaucoma Patients and Suspects
Authors: Brussell Edwara M. , Krasowski Donna , Balazsi A. Gordon , Faubert Jocelyn , White Charles W. , Muermans Myriam
Published: February 2023

There is a growing body of evidence indicating that deficits in temporal sensitivity represent an early symptom of chronic open angle glaucoma (1-4). However, the methodologies typically employed favor detection within the achromatic system. The purpose of the present study was to begin to explore the extent to which temporal sensitivity in the chromatic pathways may be sacrificed in glaucoma. The initial strategy that was adopted entailed testing pure glaucoma patients and suspects who, with at least one eye, scored within the normal range on both the H-R-R Pseudoisochromatic Plates, and the Farnsworth-Munsell 100 Hue Test. In this way, we could also clearly assess the value of measuring temporal chromatic sensitivity as compared to the use of color discrimination tests conducted under steady-state luminance conditions.
Fixation Characteristics in Macular Disease
Authors: McMahon Timothy T. , Hansen Mitchel
Published: February 2023

A general corollary of reduced central vision in the presence of macular disease is a reduction in reading rate. This exists, even in the presence of large amounts of magnification of text material. Clinically, the desire to see to read is the most common goal of patients undergoing rehabilitation for low vision. A portion of those with macular disease, particularly those with mild to moderate losses of vision, can read at acceptable rates with tolerable amounts of magnification and appropriate instruction on the use of such magnifiers. However, a substantial portion, most notably older patients, fail to achieve acceptable reading ability.
An Association between Red/Green Color Discrimination and Loss of Visual Acuity 18 Months Later in People with Unilateral Exudative AMD
Authors: Eisner Alvin , Fleming Susan A. , Klein Michael L.
Published: February 2023

The leading cause of new blindness among people aged 60 or older is age-related macular degeneration (AMD) (1). There are two forms of AMD, exudative and atrophic. Most AMD-related blindness is due to the exudative form (2), which is the potentially treatable form. When an exudative lesion is sufficiently far from the foveola, that lesion may be treated by application of laser photocoagulation (3,4). Because the distance of the exudative lesion from the foveola often decreases rapidly with time after presentation of initial symptom. (5), prompt treatment after presentation of symptoms is essential in order to maximize that treatment's chance of success. Because initial symptoms can be missed or overlooked (6), it is important that individuals know whether or not they are at especially great risk for developing exudative AMD.
Monotonic Compensation Filters Optimize Word Recognition for Observers with Age-Related Maculopathies
Authors: Lawton Teri B.
Published: February 2023

The visual function of ARM observers is assessed using the most comprehensive techniques by measuring their contrast sensitivity function.1-4 The contrast sensitivity function maps out the range of visible spatial frequencies. Only patterns composed of low and intermediate spatial frequencies can be seen by ARM observers.1-4 An ARM observer’s losses in sensitivity to intermediate and high spatial frequencies can be partially compensated for by increased magnification to aid image recognition.4 Too much magnification, however, will produce such large letters that only a few letters are able to be seen in a single glance. Therefore, reading performance deteriorates with too much magnification.5 Magnification alone is not sufficient for transmitting recognizable information to the visual cortex.6
Aging Parameters in the Human Lens Using the Scanning Fluorophotometer
Authors: Hemenger Richard P.
Published: February 2023

The computerized scanning fluorophotometer1 was designed to measure fluorescein concentration in the vitreous but is also useful for assessing the distribution in the crystalline lens of the naturally occurring fluorogen which has peak absorption in the blue and fluoresces in the green.2,3 Because this fluorogen increases in concentration with age and is associated with certain lens pathologies2,3 it has been the subject of considerable interest. With some quite reasonable assumptions concerning the properties of this fluorogen and its distribution in the lens considerable information can, in principle at least, be derived from the output of the fluorophotometer. Specifically one is able to find the approximte density (in relative units) of the fluorogen in question at each point along the central axis of the lens. In addition the transmittance of the lens at each point can be separated into the part due to absorption and the part due to light scatter and, as a consequence, the approximate density of scattering centers can be found at each point.
Analysis of ERG Parameters in Central Retinal Vein Occlusion
Authors: Breton Michael E. , Quinn Graham E. , Keene Sara S. , Dahmen Janet C. , Brucker Alexander J.
Published: February 2023

Effective treatment of the complications resulting from an ischemic condition such as central retinal vein occlusion (CRVO) may depend on the accuracy of early diagnosis. In CRVO, relative ischemia of a significant proportion of retina has been associated with ocular morbidity in the form of rubeosis iridis and neovascular glaucoma (1,2,3). Fluorescein angiography (FA) has been used routinely to determine the degree of retinal ischemia in CRVO as in other occlusive vascular diseases of the retina. However, FA interpretation, based on non-quantitative visual judgements, may lack sufficient sensitivity to detect early ischemic changes (4). The purposes of this report are: 1) to characterize the ERG parameters for CRVO and fellow eyes as to their ability to identify functionally distinct sub-groups, and 2) to compare the ERG characterization of CRVO eyes to a variety of FA caracteristics.
ERGs and VEPs in Very Low Birth Weight (VLBW) Infants
Authors: Birch David G. , Birch Eileen E. , Uauy Ricardo D.
Published: February 2023

The survival rate for very low birth weight (VLBW) infants has risen dramatically over recent years. With increased viability has come increased attention to the role of specific nutrients as causative factors for complex multifactorial syndromes such as cerebral palsy. In certain cases, the role of specific nutrients in brain development has been established. Taurine, for example, is an essential nutrient necessary for normal visual development in VLBW infants (1,2). Based on this knowledge, nutritional practices have been modified to assure an adequate taurine intake for formula-fed infants (3).
ROC Analysis Applied to Multivariate Diagnostic Tests
Authors: Massof Robert W. , Drum Bruce A. , Rubin Gary S.
Published: February 2023

The area of the relative operating characteristic (ROC) curve provides a nonparametric index of diagnostic test performance.1 The area of the ROC curve is criterion-free and corresponds to the discriminability of patient test scores from normal test scores. That is, the area of the ROC curve is equivalent to the probability of correctly identifying patient test results in a two-alternative forced-choice decision task. Because of this equivalence, ROC analysis provides for the comparison of subjective clinical judgments with quantitative test results, using the same statistic.1-2
Arteriolar Tortuosity in a Hypertensive and a Normotensive Group
Authors: Williams T. David , Cooper Susan
Published: February 2023

The arterioles of the retina are routinely assessed in ophthalmic examinations. While changes in their caliber and transparency may be evaluated during such examinations, their tortuosity is much less readily determined. Clinicians have been obliged to use subjective scales such as absent-minor-moderate-marked or the like in discussing arteriolar tortuosity.
Eccentric Photorefraction: A Method to measure accommodation in highly hypermetropic infants
Authors: Bobier William R. , Braddick Oliver J. , Atkinson Janette
Published: February 2023

A photographic method, eccentric photorefraction has been developed which allows measurement of accommodation. The method was designed for the testing of infants and young children where traditional methods such as retinoscopy are difficult to deliver since the child's attention cannot always be sustained. Eccentric photorefraction shares a common principle with previous photorefractive methods in that a small flash source illuminates the eyes of a subject some distance (eg 150cm) from the camera. In this method, the source is placed eccentrically to the limiting aperture of the camera. The camera is focussed on the subject. Depending upon the accommodation of the subject, a "crescent" of light can be photographed in the pupil margin. The position of the crescent is dependent upon whether the eye is defocussed in front or behind the camera. For a given pupil size, the width of the crescent will vary with the magnitude of the eye's defocus. The optical analysis of the method has been described.2,3 When the source is placed at specific eccentricities from the camera aperture, distinct working ranges are defined2. Measurement of a large range of accommodative responses is possible. Accurate measures of accommodation require that a calibration be made from human eyes placed at known degrees of defocus. Once the adjustment has been made the method is suitable for clinical measures of accommodation.4