bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Determination of Centerline Blood Speed in Retinal Vessels from Laser Doppler Spectra
Authors: Milbocker Michael T. , Feke Gilbert T. , Goger Douglas G.
Published: February 2023

Abnormal blood flow in the retinal vascular system is symptomatic of many ocular and systemic diseases. Blood flow is also an important indicator of the effectiveness of panretinal photocoagulation used in the treatment for proliferative diabetic retinopathy. Many methods of monitoring retinal blood flow have been developed, but laser Doppler velocimetry best satisfies the criteria of accuracy, sensitivity, and noninvasiveness.
Retinal Blood Flow Measurements Using the Blue Field Entoptic Phenomenon: Does Perceived Leukocyte Velocity Depend on Contrast and Illuminance?
Authors: Petrig Benno L. , Riva Charles E. , Furubayashi Candace K. , Cunningham. Paul S.
Published: February 2023

Noninvasive quantification of blood flow velocity in retinal macular capillaries is possible now by using the blue field simulation technique (BFST).1The technique is based on the blue field entoptic phenomenon, which allows the observation of one's own leukocytes (white blood cells, WBCs) moving in retinal capillaries. To measure the velocity of these WBCs, a precisely controlled computer generated replica of the phenomenon is presented on a color graphics monitor. The subject is asked to adjust the number and velocity of the simulated WBCs to match those of the entoptically perceived WBCs.
The Value of Color Perimetry for detecting Glaucomatous Field Losses.
Authors: Vingrys Algis J. , King-Smith P. Ewen , College of Optometry  , Benes Susan C. , Weber Paul A.
Published: February 2023

Glaucomatous damage to optic nerve fibers may be either localized or diffuse1. Localized losses typically occur outside the macular area as defects of the retinal nerve fibre layer and may prove difficult to detect using standard perimetric techniques2. Recently we report that a nerve fibre bundle defect could be detected better using equiluminous color perimetry than the usual achromatic (white) target3. This raises the possibility that color perimetry may be more sensitive in finding glaucomatous damage than the present achromatic methods, as has been reported for two cases of maculopathy4. In this paper we considered this possibility by performing static meridional (sectional) perimetry on two glaucomatous patients using white and equiluminous red and blue targets.
Saccades and Fixation Following Central Field Loss.
Authors: Whittaker Stephen G. , Cummings Roger W. , Watson Gale
Published: February 2023

When a maculopathy advances to a stage where an absolute central scotoma forms, visual performance in tasks such as reading significantly deteriorates beyond a level predicted by loss in visual acuity1,2. Lore among low vision rehabilitation specialists identifies maculopathy as particularly troublesome to manage clinically. Even after compensation for the reduced visual acuity, other visual factors may hinder performance1,3 and need to be addressed. In addition, patients may have difficulty adapting oculomotor control to use functioning peripheral retina that has requisite function and field of view. Any one of these factors might limit visual performance of a given patient. In order to rehabilitate visual performance efficiently, assessment procedures need to be developed that will identify the performance-limiting factors.
The effect of background luminance on Cone Sensitivity Functions
Authors: Yeh Tsaiyao , Pokorny Joel , Smith Vivianne C.
Published: February 2023

Wald (1964, 1966) developed an increment threshold technique to obtain test sensitivity functions for the cone spectral sensitivities. He used bright chromatic backgrounds to differentially adapt two cone types leaving the third cone relatively more sensitive. The technique was adapted by Marré for clinical use (Marré, 1972; Marré and Marré, 1972, 1973). Subsequent studies (Eisner and Macleod, 1981; Ingling and Martinez, 1981; Eisner, 1982) suggested that rapid flicker (>15Hz) is a more effective test stimulus for isolation of the spectral sensitivity of the middle-wavelength sensitive (MWS) and long-wavelength sensitive (LWS) cone types. However, isolation of MWS cones at longer wavelengths is not complete even with a rapid flicker rate (Lutze, Pokorny and Smith, 1987). In this study, linear combinations of cone sensitivity functions were fitted to sensitivity functions obtained using a Wald-Marré technique with varying background luminance levels.
Diminished Foveal Sensitivity May Predict the Development of Exudative Age-Related Maculopathy
Authors: Sunness Janet S. , Massof Robert W. , Johnson Mary A. , Finkelstein Daniel , Fine Stuart L.
Published: February 2023

Age-related maculopathy (ARM) is the leading cause of new legal blindness in the U. S. population over 60 years of age1. Visual loss in ARM comes about in several ways. Retinal pigment epithelial atrophy, referred to as the nonexudative form of ARM, is more common in the overall ARM population but it develops gradually and is responsible for only ten percent of cases developing vision of 20/200 or less. The exudative form, including pigment epithelial detachments (PEDs) and subretinal neovascular membranes (NVMs), is less common in the total ARM population, but is responsible for ninety percent of visual loss to the 20/200 level or less2.
Temporal function in age related maculopathy
Authors: Brown Brian , Lovie-Kitchin Jan
Published: February 2023

Sensitivity to temporal change in red light in elderly patients with age related maculopathy (ARM) is depressed across a wide range of temporal frequencies compared to elderly control subjects. Patients with normal acuity and pigmentary changes and/or drusen at the macula (pre-ARM) have normal temporal sensitivity.
The Stiles-Crawford Function in an Aphakic Subject with Retinitis Pigmentosa
Authors: Bailey J.E. , Lakshminarayanan V. , Enoch J.M.
Published: February 2023

The Stiles-Crawford function (Stiles, 1937) is a psychophysical measure of photo receptor orientation and directional sensitivity. It is found that the Stiles-Crawford functions are affected in various pathologies. Birch and his group (Birch, Sandberg, and Berson, 1982) found in patients with different genetic types of retinitis pigmentosa (RP; visual acuity of 20/40 or better, no visible opacities in the media) that parafoveal Stiles-Crawford Effect of the first kind (SCE I) functions were either significantly flattened or have displaced peak positions. Morphological changes have been found in photoreceptors of RP patients (post-mortem). These morphological changes could lead to an increase in the numerical aperture of the cones (acceptance angle hypothesis) and result in reduced directional sensitivity. Alternatively, patients with RP may show increased variation in the alignment of photoreceptors (with normal acceptance angles) due to fractional forces on the retina, loss of supporting structures, and/or alterational forces maintaining alignment (splaying hypothesis). If the peak of the SCE I remains near center in the pupillary aperture, one assumes that photoreceptor alignment mechanism(s), perse, are still functional even if affected. Of course, both options, changes in optical properties, and splaying can occur concurrently.
Power Spectrum of Oscillatory Potentials in Carriers of X-Linked Form of Congenital Stationary Night Blindness.
Authors: Young Rockefeller S.L. , Chaparro Alex , Price James , Walters James
Published: February 2023

Like their affected male relatives, female carriers of the sex-linked inherited form of congenital stationary night blindness are born with one defective X-chromosome; but unlike their relatives, the carriers do not express the night blindness, high myopia, or most other of the clinical symptoms associated with this genetic defect. Recently, Miyake and Kawase (1983) carefully compared the ERG responses of a large number of carriers with normal subjects. As one might expect they found that the female carriers had normal scotopic ERG a-and b-waves. Somewhat unexpectedly, however, Miyake et al found that the amplitude of the oscillatory potentials (OPs) was slightly (but statistically significantly) smaller than that of normal subjects.
Use of Circularly Polarized Light in Fundus and Optic Disc Photography
Authors: Fariza Enrique , Jalkh Alex , Thomas John , Peli Eli , O'Day Tom
Published: February 2023

Circular polarizers have been used for different ophthalmic applications such as ophthalmoscopy (1), lens photography (2), and corneal endothelial microscopy (3). To the best of our knowledge, they have not been applied to fundus and optic disc photography.
Preliminary Characterization of Human Crystalline Lens Geometry as a Function of Accommodation and Age
Authors: Koretz Jane F. , Bertasso Anne M. , Neider Michael W. , Kaufman Paul L. , Goeckner Patrick A.
Published: February 2023

Accommodation is a dynamic visual process involving the controlled deformation of the crystalline lens by the ciliary muscle. In the unaccommodated state (focus on infinity), the lens is stretched to its thinnest along the visual axis, and its curvature is at its flattest. The accommodative process, which increases the refractive contribution of the lens to the overall system, occurs through a controlled elastic recovery by the lens, resulting in increased axial lens thickness and sharpness of curvature. With increasing age, the closest focus obtainable through this process recedes, resulting eventually in the condition termed presbyopia.
Clinical Grading: Can We Do Better?
Authors: Bullimore Mark A. , Bailey Ian L.
Published: February 2023

Clinicians have a need to grade the magnitude or the severity of the functions and qualities they assess in their examinations. They do this to record the stage of the disease or condition of interest. The grade provides a reference to which any future grading may be compared and the grade may also be used in deciding deviations from normality. The clinicians questions are "is there or is there not a deviation from normality?" or "has there or has there not been a change in this condition?" The decision is whether the 'observed' finding differs from the 'expected' value. The expected value may be either a grade recorded previously or the 'normal' value. For all systems used for grading a continuous variable, there is a statistical probability that there will be a difference in the assigned grades when there is actually no difference in the two conditions being compared. Similarly, there will be times when the assigned grades remain the same even though the condition has changed.
Electroretinographic Oscillatory Potentials and Their Role in Predicting Treatable Complications in Patients with Central Retinal Vein Occlusion
Authors: Johnson Mary A. , Procope Julian , Quinlan Patricia M.
Published: February 2023

Oscillatory potentials (OPs) are small electroretinographic (ERG) wavelets that occur on the rising phase of the ERG b-wave. Thought to originate as a feedback circuit involving the bipolar, amacrine and possibly ganglion cell layers of the retina1, the potential clinical utility of OPs in diseases that preferentially affect the inner retina has long been acknowledged.2Recently, OPs were shown to be much more sensitive predictors of the development of high risk characteristics in diabetic retinopathy than were fundus features graded using the ETDRS (Early Treatment of Diabetic Retinopathy Study) classification scheme3.
Residual Cone Function in "Rod Monochromats" and the Mechanisms of Rod-Cone Interactions
Authors: Schneck Marilyn E. , Adams Anthony J. , Volbrecht Vicki J. , Haegerstrom-Portnoy Gunilla
Published: February 2023

As the intensity of steady background lights is increased, rod thresholds are elevated, until a level is reached beyond which rod sensitivity is drastically reduced with further increases in background intensity. This phenomenon, rod saturation, occurs at moderate light levels. Rod saturation occurs at lower background levels when backgrounds are flashed, that is, when there is no pre-adaptation period (e.g. Adelson, 1982). Alexander and Kelly (1984) have shown, by taking advantage of the Stiles-Crawford effect and by testing protanopes, that long-wavelength sensitive cones (LWS) contribute to rod saturation on flashed backgrounds, reducing the background intensity required to produce saturation. In fact, rod thresholds are higher on flashed than steady backgrounds at levels well below saturation.
Application of Targeted Dye Delivery to The Mapping of Retinal Hemodynamics
Authors: Zeimer Ran , Guran Theresa , Shahidi Mahnaz , Mori Marek
Published: February 2023

Since many diseases of the retina result in changes in retinal circulation, information on hemodynamics can be important in the diagnosis and the evaluation of current and new therapies. We are developing a method that would allow repeated mapping of the hemodynamics of the retinal macro- and micro-circulation. The method, named targeted dye delivery, consists of encapsulating a fluorescent dye in temperature sensitive liposomes, injecting them systemically and releasing a bolus of dye in a targeted retinal vessel by a light pulse from an argon laser. We report here on the evaluation of the method in the study of retinal hemodynamics of a primate.
Transient tritanopia in a blue cone monochromat
Authors: Verdon Wayne , Haegerstrom-Portnoy Gunilla
Published: February 2023

By adapting the eye of a normal trichromat to yellow light one can measure the sensitivity of the short wavelength sensitive (S or blue) cones. If the yellow field is turned off, the S cone mechanism does not immediately gain sensitivity as one might predict, but sensitivity is paradoxically lost. This temporary sensitivity loss is termed transient tritanopia (Mollon & Polden, 1975). The phenomenon is thought to result from the polarizing effect of the yellow field at an opponent site in the S cone pathway. Acting also on this opponent site is a "restoring force" which opposes the yellow field's effect in order to minimize polarization and thus maintain sensitivity in the S cone pathway (sensitivity is assumed to be highest when the opponent site is unpolarized). When the yellow field is decremented, signals from both M and L cones are suddenly reduced and this in turn reduces the polarizing force to the opponent site. The restoring force is now left unopposed and it continues to act for several seconds, repolarizing the opponent site and leading to transient tritanopia (Pugh & Mollon, 1979).
Does Contrast Sensitivity Predict face Recognition Performance in Low-Vision Observers?
Authors: Rubin Gary S. , Schuchard Ronald A.
Published: February 2023

Many people with low vision can read with a modest amount of magnification but are unable to recognize the faces of their friends and family. In reviewing the records of 1000 consecutive patients seen at the Wilmer Low Vision Clinic, we found that 54% of the patients reported extreme difficulty in recognizing faces. Even among low-vision patients with relatively good visual acuity, face recognition remains a problem. 47% of the patients with acuities better than 20/60 reported difficulty recognizing faces. Several investigators have suggested that reduced contrast sensitivity may be an important factor in limiting performance in everyday tasks such as face recognition. This has led to the proposal that images should be pre-filtered to compensate for the reduction in contrast sensitivity of individual low-vision observers.
Glare Susceptibility as a Function of Age: Initial Results
Authors: Harrison Joseph M. , Applegate Raymond A. , Peng Chen , Yates J. Terry , Ballentine Charles
Published: February 2023

There is a decrease in sensitivity to high spatial frequencies with aging which becomes significant above age 50(1). Repeating this study with a greater number of subjects, we have found a small but significant difference between subjects aged 20-30 and those 31-40(2). One possible explanation of the loss of sensitivity in this relatively young population is a gradual increase in the light scattering properties of the ocular media increasing disability glare(3). The purpose of this ongoing study is to test the hypothesis that the effect of disability glare on contrast sensitivity increases with age.
Automated Implicit Time and Amplitude Determination for the 30 Hz Flicker Electroretinogram: Performance in Prediction of Neovascularization in Central Retinal Vein Occlusion
Authors: Severns Matthew L. , Johnson Mary A.
Published: February 2023

The use of the 30 Hz flicker ERG as a measure of the severity of retinal vascular disorders is very attractive. The subject needs only minimal dark adaptation, the test is easier to perform than most ERG tests, and analysis of the waveform is less complicated than for many other ERG tests. 30 Hz flicker implicit time correlates well with other ERG measures associated with development of neovascularization in diabetic retinopathy and central retinal vein occlusion (CRVO). Bresnick and Palta1 have shown that the 30 Hz flicker implicit time and oscillatory potential implicit times both correlate well with development of high risk characteristics in diabetic retinopathy. Direct comparisons of 30 Hz implicit time with the ERG intensity- response sensitivity parameter, log K (r2 = 0.61, p < 0.0001) and with scotopic b-wave implicit time (r2 = 0.62, p < 0.004) in a population of 92 CRVO patients2 indicate that all of these parameters reflect the underlying pathology that places the eye at risk.
Interobserver Agreement and Observer Bias in the Acuity Card Procedure
Authors: Dobson Velma , Carpenter Nancy
Published: February 2023

The Acuity Card Procedure is a rapid, subjective method for estimating grating acuity in infants and young children. In the procedure, the child is shown a series of gray cards, 28 by 58 cm in size, each of which contains a black-and- white square-wave grating located to the left or right of a small (4 mm diameter) central aperture. The tester, who is unaware of the location of the grating on each card, watches the child's eye movements through the aperture and decides, on the basis of the child's looking behavior, which cards contain gratings that can be resolved by the child. Acuity is estimated as the spatial frequency of the finest grating that the tester judges that the child can resolve, as indicated by the child's consistent looking toward the location of the grating upon repeated presentations of the card.
Effects of Dietary Omega-3 Fatty Acids on Rod ERG Function in Very-Low-Birth-Weight Neonates
Authors: Birch David G. , Birch Eileen E. , Hoffman Dennis R. , Uauy Ricardo D.
Published: February 2023

Linoleic acid (18:2 ϖ6) and alpha-linolenic acid (18:3 ϖ3) are considered essential fatty acids (EFA) for mammals because of the inability of animal tissues to synthesize them and the resulting deficiency syndromes when they are removed from the diet. Animal tissues, especially the liver, have the necessary enzymes for EFA elongation and desaturation. As shown in Figure 1, these enzymes generate a family of compounds for each EFA: ϖ6 derivatives from linoleic acid (18: ϖ6) and ϖ3 derivatives from alpha-linolenic acid (18:3 ϖ3).
Psychophysical Performance as a Function of Age: There Really Is a Contrast Sensitivity Deficit in the Elderly!
Authors: Yager Dean , Beard Bettina L.
Published: February 2023

One of the uses of psychophysics is to learn something about the physiology of a sensory system through the behavioral responses of an observer to carefully-controlled stimuli and through the application of defined linking hypotheses. Problems of interpretation arise when there may be multiple sources of variation in the responses. Differences in visual thresholds at different ages might be the result of differences in performance as psychophysical observers, and not due to changes in the visual system itself. There also may be a change in the variability of the sensory response (intrinsic noise) while sensitivity remains constant. The particular psychophysical method used may also be critical for the interpretation of results; in particular, does the measurement depend on the subject's own criterion?
Electrophysiological Representation of the Central and Peripheral Upper Half Field
Authors: Nesfield C.J. , Harding G.F.A.
Published: February 2023

The Visual Evoked Response (VER) to upper half field stimulation has been studied by several groups who have reached conflicting conclusions as to the location, polarity and latency of the major component.
Binocular Visual Evoked Potential Acuity Estimates in Young Infants: A Comparison of Temporal Rates
Authors: Hartmann E. Eugenie , Hitchcox Susan M. , Karr Daniel J.
Published: February 2023

It is evident from animal deprivation studies that a number of physiological and anatomical changes occur in the visual cortex after birth, and that a normal "visual diet" is a prerequisite to a final mature level of functioning. Certain alterations in this normal visual diet will lead to irreparable damage in the cortical neural connections. A new importance has been attached to the intervention and treatment of early visual problems, primarily because of the proliferation of basic research studies on visual development. Eye care specialists dealing with pediatric patients have recognized the importance as well as feasibility of early evaluation of visual processing abilities and the benefits of early intervention. Qualitative judgment of fixation was, at one time, the only available measure of visual functioning in nonverbal patients. Now, however, quantitative measures of visual acuity using either behavioral or electrophysiological protocols are becoming more prevalent in clinical settings.
Design for a shoebox-size, computer-controlled, three-color temporal contrast sensitivity tester
Authors: Dagnelie Gislin
Published: February 2023

In the past few years, considerable attention has been devoted to the estimation of the human luminance impulse response function from temporal contrast sensitivity measurements1,2, and to the theoretical and practical intricacies of this technique.3,4 Recently, we have found that the shape of the foveal impulse response function in retinitis pigmentosa (RP) patients, determined through flicker sensitivity testing, correlates well with other measures of RP progression, and that it is a more precise indicator of foveal and parafoveal photoreceptor involvement than other psychophysical test procedures.5
Variations in hyperacuity performance with age
Authors: Elliott David B , MacVeigh David , Whitaker David
Published: February 2023

A recent study (Odom et. al., 1989) has suggested that the vernier acuity of an observer is independent of the individual's age. This is somewhat surprising given the evidence of an age-related decline in other measures of visual performance such as visual acuity, contrast sensitivity (Elliott, Whitaker and MacVeigh, 1990) and indeed other types of hyperacuity such as displacement detection (Elliott, Whitaker and Thompson, 1989). This type of study is, however, fraut with methodological problems. As an example, if observers are allowed the freedom to set their own level of threshold, criterion differences between observers manifest themselves as actual threshold differences. Therefore, quite justifiably, it has been suggested that a method of adjustment, the technique used by both Odom et. al. (1989) and Elliott et. al. (1989), should be avoided for age-related studies of vision (Higgins et. al., 1988). This is especially true for vernier acuity in which a method of adjustment introduces many unquantifiable variations due to the technique adopted by different individuals. For these reasons we felt that a study employing a forced-choice method of threshold measurement for several different hyperacuity tasks was important.
Use of the KOWA FC-1000 to Measure Aqueous Humor Protein and Cells in the Dog
Authors: Krohne Sheryl G.
Published: February 2023

Breakdown of the blood-aqueous barrier (BAB) resulting in protein and cells in the aqueous humor of humans and many animals has been documented.1 This breakdown occurs during uveitis, and following surgery and paracentesis. BAB breakdown occurs following these initiating insults because endothelial cells contract in the ciliary body, causing protein leakage from the vascular system which results Jn dysjunction of the epithelial layers, further vascular damage and protein leakage.2,3 These changes are mediated by prostaglandins, leukotrienes, free radicals, neurostimulators (such as in the anti-dromic reflex) and mechanical disruption.3,4,5,6 Sequelae to the BAB breakdown can be severe and include hypopyon, cataract, synechia, vitreal opacities, glaucoma, blindness and occasionally phthisis bulbi.
Noninvasive Studies of Human Visual Cortex Using Neuromagnetic Techniques
Authors: Aine C.J. , George J.S. , Supek S. , Maclin E.L.
Published: February 2023

The major goals of noninvasive studies of the human visual cortex are: (1) to increase knowledge of the functional organization of cortical visual pathways; and (2) to develop noninvasive clinical tests for the assessment of cortical function. Noninvasive techniques suitable for studies of the structure and function of human visual cortex include magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission tomography (SPECT), scalp recorded event-related potentials (ERPs), and event-related magnetic fields (ERFs). The primary challenge faced by noninvasive functional measures is to optimize the spatial and temporal resolution of the measurement and analytic techniques in order to effectively characterize the spatial and temporal variations in patterns of neuronal activity. In this paper we review the use of neuromagnetic techniques for this purpose.
What is the Utility of the Psychophysical "Light Scattering Factor"?
Authors: Yager Dean , Yuan Rumei , Mathews Steven
Published: February 2023

Vos, Walraven, and van Meeteren (1976) have proposed an empirical scattering factor for the ocular media (LSF) in terms of the illuminance on the eye from a glare source (E), an equivalent veiling luminance (Leq), and the glare angle (GA). Rearranging their equation (3) gives the following expression: Paulsson and Sjöstrand (1980) have suggested that measurements of LSF may be developed into a useful clinical index of light scatter in the ocular media by deriving an expression for LSF in terms of the contrast threshold without a glare source (M1), threshold with a glare source (M2), mean luminance of the contrast target (L), and glare illuminance (E, same as above): This calculation is intended to be unaffected by reasonable variations in L and E, because of compensating changes in contrast thresholds. Thus, it should represent an intrinsic scattering property of the ocular media. They state that this expression is valid "if we assume that psychophysical effects such as adaptation and pupil size can be neglected" (page 403).
A Sensitive Method for Quantifying Functional Loss Caused by Veiling Glare in Patients and in Elderly Nonpatients
Authors: Regan D.
Published: February 2023

Several kinds of glare are distinguished in the literature.1 This paper is concerned with glare caused by light scattered within the eye, often called "veiling glare".1 It is not self-evident that the reduction of sinewave grating contrast sensitivity produced by scattered-light glare is likely to be a good predictor of the disability caused by glare in everyday visual environments because: (1) The retinal image of objects such as an automobile or a tree contains many different spatial frequency components; (2) the ability to recognize the shape of a complex object is not well predicted by the contrast detection sensitivity for sinewave gratings,2-5 (3) it is not intuitively obvious how a contrast sensitivity loss at, say, 2 cycles/degree translates into a reduction of ability to see and recognize objects in the everyday visual environment.
Measurement of Spatiotemporal Frequency Response Characteristics in a Hemianope: (Evidence for two separate channels)
Authors: Barbur J L , Harlow A J , Weiskrantz L
Published: February 2023

Damage to the striate cortex in human subjects results in phenomenal "blindness" in corresponding parts of the retinal-cortical map. Paradoxically, in monkeys visual capacity can still be demonstrated in the affected parts of the visual field, and can be shown to be mediated by non-geniculo-striate pathways (of which there are 9 in addition to the classical geniculo-striate cortical pathway). As the same extra-striate pathways are presumed to exist in humans, the question is whether the difference in results between species depends upon the necessity to use forced-choice discrimination methods in animals.
Flicker Sensitivity Prior to Development of Exudative Age-Related Maculopathy
Authors: Mayer Melanie J. , Spiegler Shari J. , Ward Brian , Glues Andrew , Kim Charlene B. Y.
Published: February 2023

Exudative age-related maculopathy (ARM) is the leading cause of visual loss in the United States among the elderly.1,2 The goal of our research is to identify those at risk for exudative ARM in advance of any symptom of visual change. A sensitive screening test could alert those at risk to more carefully monitor their vision for early visual distortion or loss so as not to delay clinical evaluation and treatment. A sensitive test might also give information about the progress and rate of development of pre-exudative stages of ARM. And as a continuous index of retinal health (rather than a measure reflecting visual loss resulting from the end-state of macular degeneration), such a screening test could prove useful in evaluating proposed treatments for early stages of exudative ARM.
Motion Perception in Glaucoma
Authors: Bullimore Mark A. , Wood Joanne M. , Swenson Kirk
Published: February 2023

The early detection of optic nerve damage is a prerequisite for effective therapy in primary open-angle glaucoma (Kass et al., 1990). An alarmingly large proportion of retinal ganglion cells may be damaged, however, before visual field defects are observed with conventional manual or automated perimetry (Quigley et al., 1982; Quigley et al., 1989). This implies that either there is widespread redundancy within the retina such that substantial cell death can occur without loss of visual performance or that our current clinical procedures do not test the function of the cells that are damaged in early glaucoma. Recent studies lead us to believe that the latter of these two hypotheses may be correct.
L-cone discrimination and pigment tests
Authors: Smith Vivianne C. , Pokorny Joel , Yeh Tsaiyao
Published: February 2023

We have previously discussed how to express FM 100-hue test data in an S-cone discrimination space (Pokorny et al, 1990; Yeh et al, 1991). Here we extend this endeavor to L- and M-cone mediated discriminations. Additionally, we now include a variety of arrangement tests, including the FM 100-hue test, the Farnsworth Panel D-15, the desaturated Panel D-15d, and the Lanthony New Color Test. The rationale for this work lies in the observation that chromaticity discrimination is economically described (Boynton & Kambe, 1980) within the framework of the MacLeod & Boynton (1979) cone excitation space. Physiological studies in the macaque indicate that at the retinal ganglion and lateral geniculate level, chromatic processing is organized in the Parvocellular processing stream. Two major classes of cells show discrimination on two independent "cardinal axes" (Derrington et al, 1984). The macaque Parvocellular and the human cardinal axes are closely similar (Krauskopf et al, 1982). The majority of acquired color defects seen by clinicians arise from retinal or optic nerve disorders. Thus errors should develop along the major axes of cone excitation space. The purpose of this talk is to describe how the error scores on arrangement tests can be related to chromaticity discrimination mediated by relative L-cone discrimination.
Threshold and Suprathreshold Responses to Chromatic Stimuli Using Psychophysical and Pupillometeric Methods
Authors: Barbur J L , Birch J , Harlow A J
Published: February 2023

Colour difference thresholds reflect the sensitivity of the channels involved in chromatic discrimination and have been measured elegantly by MacAdam for several directions of modulation in the CIE (x,y) - chromaticity diagram from estimates of standard deviation associated with successive colour matches (MacAdam, 1942). The extent of isochromatic regions, formally associated with the direction of colour confusion lines (Pitt, 1935, Wright, 1952) can in principle be mapped out in colour discrimination experiments although in practice the luminance contrast of the test pattern as seen by colour deficient observers makes such measurements difficult to carry out. Mollon and Reffin (1989) have developed a test which overcomes largely these difficulties by following the techniques described by Stilling (Stilling, 1877) which are based on the relative insensitivity of the visual system when required to judge luminance differences between spatially discountinuous target elements, presented on a dark background field and varying randomly in luminance. We have extended this approach and eliminated the need to use a dark background field by developing a Random, spatiotemporal Luminance Masking (RLM) technique. The method employs a matrix of spatially discrete elements which form part of the uniform background field and are equal in time-averaged luminance to that of the background.
A model of the human ERG: Predicting changes in a- and b-wave amplitude and timing with congenital stationary nightblindness (CSNB)
Authors: Hood Donald C. , Birch David G.
Published: February 2023

Retinal disease can alter both the amplitude and the timing of the a- and b-waves of the ERG. Recently, Hood and Birch1 proposed a computational model, shown in schematic form in Fig. 1, to relate mechanisms of disease action to changes in the a- and b-waves. Following Granit's analysis, the a- and b-waves result from the algebraic summation of two potentials PIII (called here P3), generated by receptors, and PII (called here P2), generated by cells of inner nuclear layer (INL). A computational model of the receptor response from Hood and Birch2,3 generates P3 and is the input to a P2 generator. The ERG is the sum of the P3 and P2 responses. The model in Fig. 1 was designed to describe changes in the a- and b-waves with changes in the energy of a brief flash. In particular, the model predicts the leading edge of the a-wave, and the implicit time and trough-to-peak amplitude of the b-wave. The changes with disease were captured by changing one or more of the parameters of this model.
Isoluminance in the ERG
Authors: Wu Shuang , Sutter Erich , Reeves Adam
Published: February 2023

By definition, switching a field of a given size between isoluminant colors should trigger no response in the luminance channel. In practice, an exact zero point is not observed, and isoluminance is defined in psychophysics as the point of minimal flicker. Similarly we define ERG-isoluminance as a luminance ratio of two different colors which generates minimal ERG response when alternated. If the ERG were linear and the response wave-forms were independent of color, a luminance ratio must exist where color alternation in a stimulus field elicits no response. However, just as in the psychophysical flicker photometry, a minimum, rather than a response null, is found. This minimum defines ERG-isoluminance. The absence of a null point can be explained by the nonlinearities in the ERG response and difference in wave-form and latencies of the major response components associated with different colored stimuli. In this study deviations from linearity are ignored and only a linear approximation of the response (first order kernel) to luminance and chromatic modulation is considered, as the linear approximation accounted for about 80% of the response power.
Visual Function Evaluation of a Patient with Congenital Nightblindness and White Spots in the Fundus
Authors: Sunness Janet S.
Published: February 2023

A patient with congenital nightblindness and white spots in the fundus was evaluated in 1985 and again in 1990. This patient appeared to represent an intermediate state between fundus albipunctatus, a congenital stationary nightblindness with the special features of white spots in the fundus and prolonged dark adaptation of several hours leading to normal absolute thresholds(1,2,3), and retinitis punctata albescens, a form of retinitis pigmentosa characterized by white spots in the retina and by the functional features of retinitis pigmentosa (ring scotomas, diminished ERGs, progressive decrease of function, etc)(5). The patient was fascinating particularly in terms of 1) her dark adaptation abnormalities and the critical importance of prior recent light exposure in interpreting her visual function, 2) her evidence of cone involvement, and 3) her ERG abnormalities. The visual function tests in this patient provide diagnostic information, are critical in following her course, and provide fascinating insight into the mechanism of her disease.
A Versatile Test of Motion Perception for the Macintosh II Computer
Authors: Wood Joanne M. , Bullimore Mark A. , Swenson Kirk H.
Published: February 2023

In recent years there has been increased interest in the assement of motion perception in ocular disease. Researchers have demonstrated abnormalities of motion perception in retinitis pigmentosa (Turano, 1991), glaucoma (Silverman et al., 1990; Bullimore et al., 1991), optic neuritis (Regan et al., 1991), cerebral lesions (Vaina et al., 1990) and amblyopia (Buckingham, 1991). This motivated us to develop a simple but versatile clinical motion test which would be accessible to clinicians.
Single Channel, Sinusoidally Modulated Signal Generator, with Variable Temporal Contrast
Authors: Rynders M. C. , Thibos L. N.
Published: February 2023

Frequently in visual science experiments a stimulus is needed for which the luminance varies sinusoidally with time2, 4, 5,6, 8 set of 2 linear polarizers, one of which rotates at a constant angular velocity, is a very simple and straightforward method for producing such a stimulus, although this method only gives 100% modulation. In order to vary the amplitude of modulation, while maintaining a constant mean, previous workers have used two-channel optical systems5, split beams3,4, or used extensive electronics6, 8. However, a simple modification of the single channel polaroid method allows independent control of amplitude and mean intensity. Figure 1 shows in more detail what happens to the light as it passes through the separate components. Light passes through polarizer P and subsequently passes through quarter wavelength plate L. Because of the bireffingent properties of L, the beam of light leaving L will be linearly, elliptically, or circularly polarized, depending on the angle α between the plane of polarization of P and the fast axis of L. In the following section it will be shown that the light leaving rotating analyzer A is modulated sinusoidally in intensity, with fixed mean and amplitude depending on α. The mean may be decreased by using ND-filters.
Assessment of visual shape perception with motion, stereo, and texture cues.
Authors: Nawrot Mark , Rizzo Matthew
Published: February 2023

The assessment of visual function in neurologically impaired patients
is a difficult and time consuming procedure. Quite often these
patients are elderly or have serious health problems causing them to
fatigue rapidly. Many brain damaged neurological patients have visual
field, language, or attention deficits. Such patients may be unable to
cooperate and often continue to report on a non-tested, control aspect
of the stimulus (e.g., position instead of movement, or size instead
of color.) These are among the many reasons for a patients’s
poor performance on a psychophysical task. Nevertheless, the
combination of psychophysical techniques with modem brain imaging
techniques such as 3-D MRI reconstruction (Damasio & Frank, 1992)
of the lesions in brain damaged patients can still offer a wealth of
information about the the anatomical substrate of human visual
processing.
Double-Pulse Perimetry: Effects of temporal stimulus configuration and binocular summation*
Authors: Treutwein Bernhard
Published: February 2023

In case of multiple sclerosis the discrimination of double-pulses of
light is a more sensitive test of local damage in the visual field
than visual acuity and critical flicker fusion frequency (Galvin et
al., 1976, 1977). The same technique is also a diagnostic tool for
detecting glaucoma (Stelmach et al., 1986). Given these facts, it is
surprising that the method of double-pulse resolution is rarely used
in clinical vision research. This may be a consequence of the apparent
contradictions between a number of studies on the foveal
discrimination of double-pulses (Mahneke, 1958; Venables, 1963;
Kietzman and Sutton, 1968; Boynton, 1972), as well as methodological
problems. I tried to resolve the difficulties by measuring
double-pulse resolution by means of an extended version of the
paradigm of Stelmach et al. (1986). It allows the quasi-simultaneous
measurement of double-pulse resolution at 9 locations in the visual
field. I also employed an adaptive psychophysical procedure which
provides a maximum likelihood estimate of the threshold parameter
(Treutwein, 1989).
Infrared Imaging in Age-Related Macular Degeneration: Retinal Pigment Epithelial Detachments
Authors: Elsner Ann E. , Staurenghi Giovanni , Weiter John J. , Buzney Sheldon M. , Wolf Sebastian , Wald Kenneth J.
Published: February 2023

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the elderly (1). The loss of vision is due, in 90 % of cases, to "exudative" sequelae: retinal pigment epithelial detachments (PED) and subretinal choroidal neovascular membranes (SRN) (2).
Disability Glare Testing of Patients with Hereditary Retinal Disorders
Authors: Bane Mark C.
Published: February 2023

Low vision clinicians realize that environmental factors have a significant influence on visual performance. Visually impaired patients frequently report that glare increases the difficulty of visual tasks, and it has been shown that glare compounds problems with orientation and mobility.1,2 It is difficult for low vision clinicians to evaluate patient glare problems, because the lighting conditions that are available in clinical settings seldom represent the range of those in a patient's everyday life.
The Waterloo Vision and Mobility Study: Vision Impairment in the Control of Posture
Authors: Elliott David B. , Flanagan John G. , Patla Aftab , Spaulding Sandy , Rietdyck Shirley , Strong Graham
Published: February 2023

The control of stable upright posture is a prerequisite for many tasks of daily living. The transition from quadrupedal to bipedal stance has made this seemingly simple task far more challenging. The base of support has been reduced and the large mass of upper body is balanced high above the ground. The upright stance is regulated by three major sensory modalities, vision, vestibular and the kinesthetic system. Vision provides expropioceptive information about body movements and their relation to the environment. The vestibular system provides a gravio-inertial reference frame, detecting angular and linear accelerations of the head. The kinesthetic system is the source of information about body movements and is referred to the support surface. It is evident that there is overlapping information amongst these three modalities. When one is comprised, the other systems can compensate.
The ERG A-Wave and the cGMP Phototransduction Cascade in the Developing Infant Eye
Authors: Breton Michael E. , Schueller Albert W. , Quinn Graham E.
Published: February 2023

The leading edge of the electroretinogram (ERG) a-wave undergoes change during early development that may be interpreted in terms of photoreceptor growth and maturity of the phototransduction mechanism. The a-wave of the ERG recorded in response to a brief flash of light under dark adapted conditions has long been known to reflect the collective responses of rod photoreceptors (Granit, 1933; Hagins, Penn and Yoshikami, 1970). A variety of features of the a-wave have pointed to its photoreceptor origin. Despite understanding of the photoreceptor origin of the a-wave, application to clinical populations, including differentiating normal development from disease states in infants, has been hampered by a number of factors, including the intrusion of the b-wave, which effectively truncates the a-wave in a time- and light- dependent manner.
COLOUR DISCRIMINATION MEASUREMENTS IN PATIENTS WITH CEREBRAL ACHROMATOPSIA
Authors: Barbur J L , Harlow J A , Plant G , Williams C
Published: February 2023

Cerebral achromatopsia describes the loss of perceived colour following damage to certain areas of the visual cortex. The brain lesions causing such a syndrome are bilateral when both visual hemifields are affected and localised outside V1 in the lingual and fusiform gyri (Meadows, 1974; Zeki, 1990(a,b); Plant, 1991).
Effects of visual training on parafoveal Vernier and resolution acuity
Authors: Beard Bettina L.
Published: February 2023

Repetitively discriminating between visual patterns can substantially improve visual abilities including standard visual acuity (Saugstadt and Lie, 1964) and Vernier acuity (McKee and Westheimer, 1978; Poggio, Fahle and Edelman, 1992). Since vision training research may increase our understanding of the processing and plasticity of underlying neural mechanisms, it is important to determine if training is generalized to other stimulus conditions.
Spectra of second harmonic generation and sum frequency generation for multimode fields
Authors: Krasinski J. S. , Heller D. F. , Ackerhalt J. R. , Band Y. B.
Published: February 2023

The theory of three wave mixing was formulated in a classic paper by Armstrong, Bloembergen, Ducuing, and Pershan over 25 years ago.1 A theoretical description of three wave mixing for multimode time-dependent input fields (as opposed to cw single frequency time independent input fields) has recently been presented.2 Analytic solutions were developed for die time-dependent intensities of the output fields. These solutions differ dramatically from those for single-mode fields. New frequencies in the sum-frequency output spectrum and in the input-field output spectrum are created and grow in magnitude as the input intensities are increased. The output spectrum broadens under conditions of strong nonlinear coupling, ultimately reaching the phasematched bandwidth limit. Here, we review the results presented in Ref. 2 for sum frequency generation (SFG) and explicidy compare these results with those for second harmonic generation (SHG). We show that SHG cannot be described as a limit of the SFG formalism for multimode fields. The SFG formulation for the interaction of photons close to frequency ω1 with photons close to frequency ω2 producing photons close to frequency ω 3= ω 1+ ω 2 does not allow ω1(ω2) photons to interact with each other to produce photons close to frequency 2ω1(2ω2). This self interaction is crucial for SHG and must be incorporated. Therefore, a separate formulation is used to describe SHG with multimode input fields.
Passage Time Statistics and Scaling Laws in LSA Bistable Regimes
Authors: Papoff F. , Dangoisse D. , Fioretti A. , Arimondo E. , Colet P. , San Miguel M.
Published: February 2023

The relaxation from a marginal state has been investigated in presence of pump external noise. The experimental results have been fitted through a one­dimensional theory for a pitchfork bifurcation with additive noise.