bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the scattering characteristics of the eye in relation to pupil size
Authors: Barbur J L , Edgar D F , Woodward E G
Published: February 2023

When the amount of scattered light in the eye is large, either as a result of changes in the structure of the eye or the presence of intense sources of light, this results in significant impairment of vision, sometimes described as disability glare (Vos and Bouman, 1959; Vos, 1984). The effects of scattered light on image resolution and sharpness can be quite significant, with massive loss of sensitivity particularly in the high frequency range (Hess and Woo, 1978; Koch and Lie, 1990). A gradual increase in scattered light with age makes it possible for the visual system to adapt to a lower image contrast and hence to tolerate as acceptable a poor level of image quality (IJspeert et al, 1990). Scattered light does not cause an immediate decrease in Snellen Acuity (which is usually measured with high-contrast letters). This apparently normal performance explains why increased scatter in often undetected in routine eye examinations. The effects of scattered light on visual performance become more apparent in patients with opacities of the ocular media following refractive surgery, in cases of corneal oedema, keratoconus, cataracts and various forms of corneal dystrophy (Koch, 1989; Elliot et al, 1989). The ability to measure reliably small changes in the level and angular distribution of scattered light in the eye has been of interest clinically in monitoring the effects of drugs on media opacities or the recovery of corneal transparency following photorefractive keratectomy (Lohmann et al, 1991). In spite of what are potentially useful clinical applications for the measurement of the scatter function of the eye, the monitoring of small changes in light scatter parameters has not been very successful in a clinical context, the level of variability being very high (Elliot and Bullimore, 1993). One aim of the present study is to investigate the extent to which measured variability can be attributed to instrumentation and measurement error or to genuine changes in the pattern of scattered light in the same eye. In addition, the scattering of light may not always be uniform over the pupil, as a result of non-uniform distribution of ocular opacities and scattering centres. Measuring the effect of pupil size on light scatter is therefore important and may account for some of the observed variability. Unless the size of the pupil is known at the time of measurement, and its effects accounted for, small changes in light scatter parameters (i.e., the k and n values below) cannot be separated from the effects of pupil size, and hence they cannot be attributed easily to other factors under investigation. Another aim of this study was therefore to investigate the effect of pupil size on the scatter function of the eye.
Flicker Sensitivity in Patients with Retinitis Pigmentosa and Good Acuity
Authors: Swanson William H. , Fiedelman Marilyn , Fish Gary E.
Published: February 2023

Retinitis pigmentosa (RP) is a retinal degeneration which can be produced by a large number of different genetic mutations. In the early stages rod photoreceptor function is more severely impaired than cone photoreceptor function, and the rate of degeneration is faster for rods than for cones. Although the end stage can be complete loss of light perception, visual acuity often remains relatively unaffected despite severe loss of peripheral visual function.
Fourier components of the pupillary response and their relationship to temporal characteristics of luminance and chromaticity processes
Authors: Fang Lie-Yi , Young Rockefeller SL
Published: February 2023

In humans, the pupil does not only responds to changes in luminance levels, but also respond to isoluminant color changes (e.g., Kohn and Clynes, 1969; Young and Alpern, 1980). This raised new possibilities regarding the nature of the underlying visual process, such as some aspects of the process may be "color-opponent", there may be multiple processes with different preferences for luminance and chromaticity, or the underlying visual process may be mediated by phasic (M-like) and/or tonic (P-like) visual neurons.
Evidence for My-cell Involvement in the Spatial Frequency Doubled Illusion as Revealed by a Multiple Region PERG for Glaucoma
Authors: James AC , Maddess T , Rouhan K , Bedford S , Snowball M
Published: February 2023

Recent evidence suggests that glaucoma leads to early loss of large retinal ganglion cells1,2 projecting to the Magnocellular layers of the dLGN: the so called "M" retinal ganglion cells. It is necessary for the present study, to appreciate that there are two subgroups of M-cells, the Mx-cells which are quite linear, and the nonlinearly responding My-cells, where the subscripts indicate physiological similarities with cat X and Y-cells3. In particular the retinal gain control described by Shapley and Victor4 for cat X and Y cells is strongly expressed in primate M- cells5. Except at very low temporal frequencies the quadratic response of Y-cells is larger than the linear response, especially at low spatial frequencies6, and the gain control effects Y-cells more, especially their quadratic response7. At least three studies indicate that My-cells are larger than Mx- cells8,9,10. Therefore, methods for glaucoma diagnosis should perhaps appeal to My-cell physiology, e.g. the strong effects of gain control upon their nonlinear responses.
Letter Strokewidth, Spacing, and Legibility
Authors: Arditi Aries , Cagenello Ron , Jacobs Bradley
Published: February 2023

The development of computerized typography has revolutionized our ability to create type designs, in facilitating both the rapid design of new fonts and the alteration of their characteristics almost infinitely[10, 13]. Although type designs vary for a variety of reasons, their primary purpose is to serve as the elements of text-coded communication. Legibility is a general term that refers to the effectiveness of typography in communicating the text code. It can be defined and measured in several ways, including direct judgment, reading speed[11, 3, 9], and visual acuity [16].
Binocular Preferred Retinal Loci: Relationship of Visual Factors to Binocular Perception
Authors: Schuchard Ronald A. , Tekwani Navin , Hu Sidney
Published: February 2023

In an eye with a central scotoma, the development and use for foveal visual tasks of one or more preferred retinal loci naturally and reliably occurs (Cummings, Whittaker et al., 1985; Timberlake, Mainster et al., 1986; Timberlake, Peli et al., 1987; Whittaker, Budd et al., 1988; White and Bedell, 1990; Schuchard and Raasch, 1992; Fletcher, Schuchard et al., 1993; Schuchard, 1993; Schuchard, 1994). The term preferred retinal locus (PRL) is reserved for those individuals who have chosen a preferred retinal area to act as a pseudofovea for foveal visual tasks (e.g., fixation and reading) due to a macular scotoma affecting visual performance. Previous studies have shown that 40% of low vision patients have central scotomas and thus probably have developed an eccentric PRL (Schuchard, 1993). These previous investigations of preferred retinal locus have studied each monocular PRL separately but individuals typically perform activities of daily living with both eyes open. Therefore the research laboratory investigations of preferred retinal loci (PRLs), to date, have forced individuals to perform visual tasks monocularly without fully understanding the consequences for the monocular PRL data collected.
Different Fixation-Acuity-Scotoma Patterns can be Distinguished in Age Related Macular Degeneration
Authors: Van de Velde Frans J. , Jalkh Alex E.
Published: February 2023

The identification of different fixation, acuity and scotoma patterns is important because it may influence decision making in laser treatment. By the same token it can assist in the implementation of low vision rehabilitation strategies for ARMD. Although some detailed studies of fixation and scotoma patterns in ARMD have been published using the scanning laser ophthalmoscope, they basically reported the findings on some cases in detail, exposing the technology involved, and pointing out the fundamental advantage of using the scanning laser ophthalmoscope. Namely, the SLO permits an unambiguous localization of stimuli and a continuous observation under approximate natural conditions. Detailed off-line analysis of data involving the correction for fixation shifts and reaction time was performed in these studies. We adapted, essentially simplified microperimetric techniques for a clinical research setting: a maximum of about twenty minutes can be devoted to each eye exam, probably the limit of what a patient can endure. During each session, fixation, scotoma distribution and visual acuity were assessed using the scanning laser ophthalmoscope. This pilot study attempts to find out on a somewhat larger database of patients whether consistent patterns of fixation, scotoma and acuity exist in macular disease. Primary goals are the building of a preliminary classification system to be used in further analysis of functional deficits in macular disease and figuring out how the knowledge gained could possibly influence treatment strategies. Treatment modalities are essentially limited to two possibilities: low vision rehabilitation - after the anatomical and functional damage has occured - and either preventive or therapeutic application of lasers. Pre-treatment microperimetry information may help decide whether to treat and how to treat, post-treatment microperimetry information could serve as a follow-up to see whether treatment was successful or not.
A Statistical Method to Quantify Drusen in SLO Images
Authors: Elsner Ann E. , Remky Andreas , Beausencourt Eva , Burns Stephen A.
Published: February 2023

Drusen are the hallmark of age-related macular degeneration, which is the major cause of severe vision loss in older adults in industrialized countries (1). However, the accurate quantification of drusen with standard clinical photography is possible in only a small portion of patients (2), since media changes in elderly subjects degrade image quality. Thus, for both research and patient management purposes, an alternative method of imaging the fundus with infrared light (3) and a scanning laser ophthalmoscope has been developed to visualize subretinal structures (4-5). This imaging technique minimizes both media changes and masking of foveal drusen by macular pigment, since there is a reduced absorption of infrared light by most ocular pigments.
Accommodation in the Oscar, Astronotus ocellatus
Authors: Andison M. E. , Sivak J. G.
Published: February 2023

Highly visual, aggressive feeders such as the oscar, Astronotus ocellatus, need a well-developed and effective accommodative apparatus. Since the refractive power of the cornea becomes negligible when the eye is immersed in water, the spherical lens of the teleost eye is its primary refractive element and has a high refractive index (Sivak 1980). The fish eye provides a unique opportunity to study accommodation since the lens is easily visible within the eye. A smooth muscle, the retractor lentis, controls the position of the lens with respect to the retina. In its contracted state, the retractor lentis muscle pulls the lens temporally toward the posterior retina for viewing far targets. As the muscle relaxes, it allows the lens to move both laterally and nasally away from the retina and toward the cornea for viewing near targets.
Ocular Refractive Development Affects Skull (Orbital) Development
Authors: Wilson K.T. , Sivak J.G. , Callender M.G.
Published: February 2023

Experiments carried out over the last two decades have shown that it is possible to induce refractive errors in the eyes of young animals by distorting early visual experience. Because of their precocial nature and the fact that they grow and develop rapidly, domestic chicks (Gallus gallus domesticus) have been used extensively in this research. Earlier work involved depriving the developing eye of clear form vision, either by suturing the eyelids together or by mounting a translucent occluder over one eye (Lauber and Oishi, 1987; Pickett-Seltner et al., 1988). This treatment invariably leads to an axial elongation of the eye and myopia (near-sightedness). More recently, it has been shown that it is possible to induce both myopia and hyperopia (far-sightedness) in chicks by defocussing the retinal image of the developing eye with convex and concave spectacle lenses (Schaeffel et al., 1988). The range of refractive errors induced was extended through the use of lightweight contact lenses mounted over the treated eye (Irving et al., 1992). Basically, a concave lens simulates the condition of hyperopia, causing a compensatory increase in eye growth with the result that the eye is myopic when the lens is removed. The opposite occurs (ie. a slowing of eye growth) with convex lenses. Experiments have shown that newly hatched chicks will compensate accurately (within 4 to 7 days) to defocus of between -10 and +15 diopters (Irving et al., 1992). Astigmatic refractive states can also be induced with cylindrical defocussing lenses (Irving et al., 1995). The astigmatic effect displays a meridional sensitivity and is due to induced corneal astigmatism, possibly coupled with some lenticular astigmatism. While these studies have addressed changes in refractive state and dimensions of the eye, virtually no attention has been directed to the effects of these changes on the surrounding orbital tissues, notably the bones of the orbit. In the following report, we demonstrate that, in the chick, ocular growth and development is coupled to growth and development of the orbits.
Influence of decentration on the visual performances of aspherical single vision lenses
Authors: Rossier C. , Le Saux G. , Jurkiewiez F.
Published: February 2023

For esthetic reasons, thin and flat lenses are more and more requested by the wearers. Aspherization makes it possible to maintain a high optical quality for such lenses.
Progressive addition lenses with aspherical prescription surfaces
Authors: Baumbach P. , Brosig J. , Guilino G.
Published: February 2023

In contrast to the trial case lenses of a trial frame or a phoropter, eyeglass lenses in wear have to provide the patient with the prescribed diopter values for sufficiently large fields of view. Traditional spherical or toric prescription (Rx) surfaces cannot always meet this demand, particularly in the case of progressive addition lenses (PALs). The following paper will show the benefits of aspherical or atoric Rx surfaces for PALs with regard to optical and cosmetic features.
Theory for Evaluation of the Corneal Shape in Laser Keratopography
Authors: Díaz-Uribe Rufino , Granados-Agustín Fermín
Published: February 2023

The evaluation of the topography of the anterior surface of human corneas has up till now relied hevily on the use of Placido's disk. This method has certainly helped physicians to diagnose some refractive diseases and be more confident about the outcome of refractive surgery. For many years the evaluation was only qualitative, but in recent years it has become quantitative. Today, powerful commercial systems are present in all the relevant institutions. Recently, the main limitations of systems based on Placido's disk have been recognized and there are serious efforts to improve or substitute it with systems based on different principles. Several proposals for new systems have been made ranging from interferometry1,2, to the rasterstereographic imaging3. One main drawback of all of these methods, however, including that based on Placido's disk, is that they take one image of all the points at once. In most cases this is not a problem, but when the anterior corneal surface present severe deformations, it is difficult or impossible to compute its shape.
Fixation Preference and Grating Acuity in Strabismic Children
Authors: Salomão Solange R. , Berezovsky Adriana , Everett Mary E. , Birch Eileen E.
Published: February 2023

Monocular visual acuity (VA) measurement is a useful part of pediatric ophthalmologic assessment. In the last three decades, different methods have been developed to provide this important information (Dobson & Teller, 1978; Marsh-Tootle, 1991; Fulton et al., 1993). Preferential looking (PL) is a behavioral method used in several experimental and clinical studies to quantify VA (Jacobson et al., 1982; Birch et al., 1990; Dobson et al., 1990). Information about amblyopia and visual deficit can be obtained by PL, comparing the results with normative data for VA development and interocular acuity differences, but there is some controversy about its value in the diagnosis of strabismic amblyopia (Ellis et al., 1988; Moskowitz et al., 1987; Moseley et al., 1986). Fixation preference is considered the most reliable clinical method to diagnose amblyopia in infants and non-verbal strabismic patients (Jacobson et al., 1982; Wright et al., 1986). Occlusion of one eye while the other is fixating a target is used to evaluate if the fixation behavior of that eye is central, steady and mantained.
Influence of blood glucose level on chromatic VEP's in Type I diabetes
Authors: Schneck Marilyn E. , Fortune Brad , Crognale Michael , Switkes Eugene , Adams Anthony J.
Published: February 2023

In diabetes, changes in the function of the short-wavelength sensitive system (S-pathway) precede changes in more standard measures of visual function and may be observed prior to, or in the absence of, diabetic retinopathy (e.g. Adams, 1982; Zisman and Adams, 1982). Diabetes is fundamentally a metabolic disorder, characterized by elevated blood glucose. It is reasonable then, to consider the altered metabolic state of the diabetic as the underlying cause of the early loss of S-cone sensitivity. It has, however, proven difficult to separate metabolic from structural bases for the early vision loss, because l)the development of retinopathy is itself affected by metabolic control, and 2) vascular changes may be present though undetected in people with 'no retinopathy'.
The Effect of Light Adaptation on Recovery Kinetics of the Human Rod Photoresponse
Authors: Birch David G. , Pepperberg David R. , Hood Donald C.
Published: February 2023

In the human ERG, the leading edge of the rod a-wave reflects the mass response of the rod photoreceptors.1 It can be fit with a computational model of the activation phase of transduction to provide parameters analogous to those obtained from individual photoreceptors in vitro.2-4 However, the photoreceptor response extends for at least several hundred milliseconds following a flash5 and is obscured over much of its extent by post-receptoral ERG components. It is only when the test flash is extremely intense (above approx. 4.0 log sc td-s) that the a-wave reaches its maximal saturated amplitude prior to the onset of the b-wave. We have shown previously that it is possible to use a two-flash paradigm to probe the recovery phase of the photoreceptor response.6 Our previous work focused on recovery from intense flashes under dark-adapted conditions, where recovery may be limited by the lifetime of activated rhodopsin. The present study extends this analysis to dimmer test flashes and determines the effects of light adaptation on the inactivation phase of the rod photoresponse.
The trailing edge of the photoresponse from human cones derived using a two-flash ERG paradigm
Authors: Hood Donald C. , Birch David G. , Pepperberg David R.
Published: February 2023

Human receptor activity is open to analysis using the ERG. The leading edge of the a-wave provides a measure of the first 10 to 20 ms of the photocurrent response of both the rod and cone receptors. The complete wave form of the receptor response is obscured in the ERG by other potential, including the b-wave. Recently, however, a two-flash paradigm was used to trace out the recovery phase of the human rod photoresponse1. Here we adapt this paradigm to examine the trailing edge of the photoresponse of the human cones.
Instrument for MTF Measurements of Cataractous Eyes
Authors: Magnante Peter , Fadden Barry
Published: February 2023

With approximately 1.5 million cataract surgeries performed each year in the United States, there is great need for a non-invasive ophthalmic instrument that measures objectively the inability of a cataractous eye to produce clear images. We describe here the construction and operation of a new instrument which meets this need. Called the Ocular Resolution Analyzer (ORA), the instrument projects a fine line on a patient's retina, records the blurred retinal line image, and quantifies the extent of blurring by computing the Modulation Transfer Function. In clinical tests on cataract patients, increased blurring measured by the ORA has been shown to correlate with other indicators of cataract development: 1) increasing lens opacification as observed with a slit lamp,1 2) loss of visual acuity,2 3) loss of contrast sensitivity, and 4) increased glare sensitivity.3
Motion VEP in Infantile Esotropia Before and After Surgery: Preliminary Findings
Authors: Salomão Solange R. , Berezovsky Adriana , Birch Eileen E.
Published: February 2023

Infantile esotropia is a constant convergent strabismus that occurs early in life and affects a considerable number of infants (Mohney et al., 1995). This condition can be accompanied by several motor (crossed fixation, dissociated vertical deviation, etc.) and sensorial abnormalities (absence of binocular vision and stereopsis). Early surgical eye alignment is recommended to avoid permanent sensorial deficits, mainly in binocular vision. Recent studies of patients with infantile esotropia have reported nasalward/temporalward bias in OKN responses, smooth pursuit, VEP motion responses, and motion perception (Demer and von Noorden, 1988; Tychsen and Lisberger, 1986; Norcia et al., 1991).
The Temporal Characteristics of Eye Growth Control Mechanisms Differ Following Optic Nerve Section
Authors: Troilo David , Francis Ellie , Yi Glara
Published: February 2023

The visual control of eye growth and refractive development occurs on at least two levels, a peripheral mechanism local to the eye and retina, and a higher level mechanism possibly involving brain-mediated mechanisms. The loss of the higher level mechanism following optic nerve section results in (1) more rapid development of form deprivation myopia and (2) a reduction in the responsiveness of choroidal and axial growth responses to visual signals. These results suggest that the peripheral mechanism, while capable of responding to coarse visual stimuli, is normally modulated by the higher level mechanism.
Improvements to and reliability of a new computer assisted crossed-cylinder aberroscope
Authors: Cox Michael J , Walsh Glyn
Published: February 2023

In this paper we present developments and reliability tests of a method for the derivation of the wavefront aberration of the human eye using the aberroscopic technique described by Howland1 for the evaluation of photographic lenses, which was subsequently modified for use on the human eye both subjectively2,3 and objectively4,5. We use a solid-state imaging device linked directly to a desktop computer to allow immediate and automated analysis of the image.
Completely Dioptrically Equivalent Systems
Authors: Keating Michael P.
Published: February 2023

The paraxial optics of astigmatic human eyes is covered by the optics of systems with obliquely crossed toric surfaces. For these systems, the dioptric parameters in terms of the 2 X 2 dioptric matrices are: the equivalent power matrix P
e
(which may be asymmetric), the back vertex power matrix P
v
, and the neutralizing or front vertex power matrix P
n
.1,2 For statistical considerations where thickness is taken into account (as opposed to a thin lens model), one might compute a mean P
e
, P
v
, and P
n
(10 known parameters).3,4 Since the means are statistical calculations and not optical calculations, the question then arises as to whether any real system of toric surfaces has the same dioptric parameters as these means. I'll refer to such matching systems as completely dioptrically equivalent (CDE) systems. These systems might be models of astigmatic eyes or general systems consisting of toric surfaces.
Visual evoked potentials of metameric whites
Authors: Biondini A.R. , de Mattiello M.L.F. , Salinas H.
Published: February 2023

Metameric1 whites are white stimuli with the same tristimulus values but different spectral distribution.
Elevation of Vernier thresholds during image motion depends on target configuration
Authors: Bedell Harold E. , Chung Susana T.L.
Published: February 2023

Under a range of stimulus conditions, the threshold for discriminating spatial offset in a Vernier target is finer than the retinal photoreceptor mosaic, the defining characteristic of a hyperacuity (Westheimer 1975, 1979). Over the past several years, evidence has accumulated that the visual system achieves fine Vernier thresholds using different mechanisms, depending upon the characteristics of the stimulus. The most acute Vernier thresholds, obtained for highly visible, abutting line targets in the fovea, are thought to be mediated by the contrast responses of oriented cortical filters that straddle the Vernier offset (e.g., Findlay 1973; Wilson 1986; Waugh et al. 1993). Thresholds are higher, but can remain within the hyperacuity range, when the Vernier targets are separated by more than a few min of arc (e.g., Sullivan et al. 1972; Klein & Levi 1987; Levi & Klein 1990; Waugh & Levi 1993) or have opposite contrast polarities (O'Shea & Mitchell 1990; Levi & Waugh 1996). The thresholds obtained under these stimulus conditions have been attributed to a local-sign mechanism that separately computes the locations of the individual Vernier elements and then compares these position signals (Klein & Levi 1987).
Why We Need to Pay Attention to Psychometric Function Slopes
Authors: Tyler Christopher W.
Published: February 2023

One of the key tools of noninvasive visual assessment(\p)(p) is the measurement of visual thresholds in a variety of test targets, including letter acuity charts, perimetric visual fields, spatial and temporal sensitivity functions, color discrimination thresholds and so on through many variants. Implicit in the measurement of any threshold (of either the detection or discrimination type) is a psychometric function of percent correct versus stimulus strength. A neglected variable in the analysis of psychometric data is the steepness of the psychometric function, which is usually assumed to be fairly stable across conditions and observers and therefore to play little role in determining the measured sensitivity levels and their disturbances by eye disorders.
The Retinal Topography of Local and Lateral Gain Control Mechanisms
Authors: Sutter Erich E. , Bearse Marcus A.
Published: February 2023

The human retina is able to perform over a luminance range of approximately 1:1010.
Area Under the Log Contrast Sensitivity Function (Aulcsf) in Radial Keratotomy (Rk): Gains And Losses
Authors: Applegate Raymond A. , Hilmantel Gene , Howland Howard C.
Published: February 2023

Last year at this meeting we presented a paper entitled “Area under log contrast sensitivity function (AULCSF): A concise method of following changes in visual perfor­mance” (Applegate et. al., 1997).
Sustained Masking More Local than Transient Masking in a Spatio-Temporal Discrimination Model
Authors: Ahumada Albert J. , Beard Bettina L. , Eriksson Robert
Published: February 2023

To fit a spatio-temporal discrimination model to masking data the sustained channel contrast masking was made more local than that of the transient channel.
Accommodation to perceived depth in stereotests
Authors: Charman W. N. , Koh L-H
Published: February 2023

It has been known since the time of Wheatstone1 that, when a pair of two-dimensional (2D) images in which some regions possess appropriate disparity is presented so that each eye sees only one image, the viewer perceives a corresponding three-dimensional (3D) figure: numerous methods have since been devised to present appropriate stereopairs2. It is reasonable to ask if fixation by a young observer on those parts of the fused 3D figure which appear to lie in a different plane to that of the 2D stereopair will cause an appropriate change in accommodation. If this does occur, the retinal images of the 2D stimuli will blur, since the eye will no longer be focused on the plane of the 2D stimulus. This mismatch between the desirable levels of accommodation and convergence may lead perhaps to fatigue or to a weakening of the 3D percept3-5. For larger disparity stereo pairs there is already evidence that "appropriate " accommodation responses do occur to perceived depth6,7. The aim of the present study was to explore whether similar effects can be detected when clinical stereo tests in which images presenting lower levels of disparity are viewed and to evaluate the possible significance of any accommodation effects observed.
How Big Must Letters be for Patients with Central Field Loss to Read Rsvp Text at their Maximum Rate?
Authors: Aquilante Kathy , Yager Dean , Morris Robert
Published: February 2023

Dynamic text displays like Rapid Serial Visual Presentation (RSVP) and SCROLL are well suited to the study of reading by low vision patients because text can be magnified to sizes that are not practical for conventional page formats, while maintaining acceptable working distances (Fine and Peli, 1995). Even at high magnification, a video display with scrolling text may allow four to six characters to be displayed at one time. A four to six character window size has been found to be the minimum window size that allows low vision readers to obtain near maximum reading rates for drifting text (Legge, et al., 1985).
The Effect of Age and Eccentricity on Layer-by-Layer Perimetry: Modulation-Induced-Desensitization
Authors: Comerford James P. , Thorn Frank , Malloy Chris
Published: February 2023

Layer-by-Layer perimetry (Enoch et al, 1981) consists of a battery of psychophysical tests for evaluating visual function. These tests include the Westheimer effect, Modulation Induced Desensitization (MID), and the Flashing Repeat Static Test (FRST). In his original work developing Layer-by-Layer perimetry, Enoch called the Westheimer effect the Sustained-like function and called MID the Transient-like function, but these terms convey unnecessary implications about neurophysiological function.
Color Vision Plate Tests with Short Exposure Duration
Authors: Yamade Shinichi , Kono Momoyo
Published: February 2023

Critical exposure duration for the test targets in measurement of visual function is sometimes very important, because even though patients demonstrate relatively high levels of visual acuity using conventional methods, they may for example occasionally require longer stimulus duration for proper reading of the acuity targets. In our previous study1) we reported that the critical duration of Landolt 'C' visual acuity was significantly prolonged in eyes with central serous retinochoroidopathy and macular edema. But the critical duration for the increment threshold was not prolonged in these diseased eyes, although the mean relative threshold energy of the diseased groups was significantly higher than that of the control group. We then measured the critical duration of achromatic2) and chromatic) grating visual acuity in a normal eye, with the purpose of clarifying the mechanisms behind these phenomenon. The critical duration of achromatic grating visual acuity in the normal subject was 73.0 and 140 msec under two different brightness conditions (Fig. 1), and these were significantly shorter than the results of the Landolt ‘C’ visual acuity test (0.62 sec., n=17 as shown in Fig. 2). The critical duration of red-green grating acuity under the 4 different conditions in the same subject was 129, 134, 136 and 129 msec (ARVO 1997, Fig. 3). These were similar to one result in the achromatic grating study (140 ms, white background=23.2 cd/sqm, contrast=73.1%).
A Generalized Image Processing Application for the Enhancement of Images for the Visually Impaired
Authors: Kennedy Andrew J. , Leat Susan J. , Jernigan M. Ed
Published: February 2023

Research into digital image enhancement in the School of Optometry at the University of Waterloo and its effects on low vision subjects’ spatial perception has led to the creation of an image processing tool called ImageLab. This tool has been designed to provide image processing functions in a sufficiently general fashion to enable it to be used for research into the efficacy of various digital image enhancement effects in improving perception in people with low vision and with vision losses due to normal aging. This paper describes work currently in progress and a tool which provides functions of general interest to those in vision research. The tool and effects of different image processing algorithms on colour images are described.
The distinction between measures of active and passive dark focus and their relationship to optimal accommodative performance
Authors: Andre Jeffrey T. , Owens D. Alfred
Published: February 2023

Since the early 1970s, researchers have been measuring the resting state of accommodation (e.g., Leibowitz & Owens, 1975a, 1978; Epstein, Ingelstam, Jansson & Tengroth, 1981; Heron, Smith & Winn, 1981), operationally defined by Leibowitz & Owens (1975b) as the "dark focus" of accommodation. They proposed that the dark focus could explain anomalous refractive errors that occur in difficult visual conditions such as at night, looking at an empty field or working with an instrument. Based on this concept the dark focus could serve as a basis for predicting and correcting such “anomalous myopias” (Leibowitz & Owens, 1975b; Owens & Leibowitz, 1976). Later studies questioned the clinical utility of the dark focus, however, because different measurement techniques yield varying results. Laser optometers typically find more “myopic” dark focus values, while infrared optometers (e.g., Canon R1) obtain more distant dark focus values (e.g., Post, Johnson, & Tsuetaki, 1984; Post, Johnson, & Owens, 1985).
Tscherning Ellipses extended to Acuity Drop, Distorsion and Chromatism using Ray Tracing
Authors: Francois Sandrine , Bourdoncle Bernard , Le Saux Gilles , Miege Christian
Published: February 2023

Single vision ophthalmic lenses introduce optical aberrations which might perturb the wearer. The most perturbing are oblique astigmatism, power error, chromatism and distortion [1].
Manipulation of photon-atom momentum entanglement
Authors: Guo Hong , Guo Rui
Published: February 2023

We propose some schemes to coherently enhance atom-photon momentum entanglement with either resonant photon scattering or spontaneously induced quantum interference. A novel feature called “phase entanglement” is reported, for which the traditional R-ratio-based entanglement detection becomes inadequate due to the quantum interference.
Non-Markovian Reduced Dynamics and Entanglement Evolution of Central Spin Models in Quantum Spin Environments
Authors: Goan Hsi-Sheng
Published: February 2023

We discuss two central spin models coupled, respectively, to a quantum Heisenberg XY spin star environment [1] and to an antiferromagnetic environment [2]. In the first model [1], the exact quantum dynamics of the reduced density matrix of two coupled spin qubits in a quantum Heisenberg XY spin star environment in the thermodynamic limit at arbitrarily finite temperatures is obtained using a novel operator technique. In this approach, the transformed Hamiltonian becomes effectively Jaynes-Cumming like and thus the analysis is also relevant to cavity quantum electrodynamics. This special operator technique is mathematically simple and physically clear, and allows us to treat systems and environments that could all be strongly coupled mutually and internally. To study their entanglement evolution, the concurrence of the reduced density matrix of the two coupled central spins is also obtained exactly. It is shown that the dynamics of the entanglement depends on the initial state of the system and the coupling strength between the two coupled central spins, the thermal temperature of the spin environment and the interaction between the constituents of the spin environment. We also investigate the effect of detuning which in our model can be controlled by the strength of a locally applied external magnetic field. It is found that the detuning has a significant effect on the entanglement generation between the two spin qubits.
Geometry of Quantum Entanglement
Authors: Życzkowski Karol
Published: February 2023

A geometric approach to investigation of quantum entanglement is advocated. Analyzing the space of pure states of a bipartite system we show how an entanglement measure of a gives state can be related to its distance to the closest separable state. We study geometry of the (N2 - 1)-dimensional convex body of mixed quantum states acting on an N-dimensional Hilbert space and demonstrate that it belongs to the class of sets of a constant height. The same property characterizes the set of all separable states of a two-qubit system. These results contribute to our understanding of quantum entanglement and its dynamics.
Approaches to Non-Markovian Quantum Open Systems: From Quantum Trajectories to Master Equations
Authors: Yu Ting
Published: February 2023

In this tutorial, I will review some recent progresses in non-Markovian dynamics of quantum open systems. I will be focused with non-Markovian quantum trajectories and non-Markovian master equation approaches. In particular, I will show how to derive an exact non-Markovian master equation from the corresponding quantum trajectories. I will also show how to use quantum trajectories to derive the well-known Kraus operators for pure dephasing noise. The applications of quantum trajectories to quantum information and decoherence will be briefly reviewed.
Dynamical Localization and Environmental Noise: a Quantum Trajectory
Authors: Jun Jin Woo
Published: February 2023

Using the quantum trajectory approach, we study the effects of environmental noise on dynamical localization in a quantum algorithm simulating the kicked rotator. We apply two models that generalize single qubit noisy channels, like phase flip and amplitude damping, to the many-qubit situation. Our numerical results show that the quantum trajectory approach is suitable for simulating the quantum kicked rotator in realistic environments.
New Perspectives in High-Power Optical Fiber-Amplifiers and Solid-State Laser Cooling
Authors: Kashyap Raman , Nemova Galina
Published: February 2023

To overcome the limiting constraints on output powers placed by stimulated Raman scattering (SRS) and stimulated Brilluoin scattering (SBS), new fiber designs and techniques are presented [1], Fiber laser induced solid-state cooling [2-3] is another research area that is limited by many material problems, such as phonon assisted thermalisation and relaxation. In order to increase the cooling efficiency, novel structures must be implemented not only to address these issues, but to enhance cooling with designs that are practical.
Applications of Long Period Gratings in Solid Core Photonic Bandgap Fibers
Authors: Kuhlmey Boris T. , Luan Feng , Lazaro Jose M. , Fu Libin , Eggleton Benjamin J. , Yeom Dong-Il , Coen Stephane , Wang Aimin , Knight Jonathan C.
Published: February 2023

Solid core photonic bandgap fibres are photonic crystal fibres with a solid core surrounded by high index inclusions. The guidance properties of these fibers are very sensitive to the refractive index of the inclusions, making them widely tunable and making them very promising for sensing applications. Combining these fibers with long period gratings unleashes their full potential, enabling narrow band notch filters tunable over hundreds of nm, refractive index sensors with sensitivity comparable to that of surface plasmon resonance sensors, but also the extraction of the full band diagrams of these bandgap fibres.
Spectral Response of FBG Written in Specialty Single-Mode Fibers
Authors: Torres Pedro , Botero-Cadavid Juan F. , Vélez Francisco Javier
Published: February 2023

In this work, we describe the spectral properties of fiber Bragg gratings (FBGs) in Hi-Bi PANDA fibers subjected to diametrical compression and fibers with internal electrodes, as two examples of the facilities offered by specialty single-mode fibers for processing optical signals. Due to the complex structure of the fibers, the induced effects on the fiber effective birefringence are presented and discussed, based on numerical analysis with the finite element method.
Progress in the Fabrication of the Next-Generation Soft Glass Microstructured Optical Fibers
Authors: Ebendorff-Heidepriem Heike , Moore Roger C. , Monro Tanya M.
Published: February 2023

We report the fabrication of new soft glass microstructured optical fibers for sensing, high-nonlinearity and mid-infrared applications. The fibers were produced using the extrusion technique and a wide range of glass compositions. They demonstrate a wide variety of structural features and low propagation loss.
Highly Nonlinear Fibers in All-Optical Modulators
Authors: Hernández-Cordero Juan , Chen Lawrence R. , Rochette Martin
Published: February 2023

We demonstrate the advantages of using a Highly Nonlinear Fiber (HNLF) in an all-optical modulator based on a nonlinear optical loop minor (NOLM). The use of a HNLF allows for a compact design, since a low pump power and a relatively short length of fiber are required in order to obtain optimal switching conditions for the NOLM. Furthermore, the low dispersion and dispersion-flattened features of the HNLF offer increased flexibility for operating the modulator since walk-off effects between the pump and the signal are significantly reduced. The modulator was incorporated in a tunable mode-locked semiconductor fiber laser (SFL) and its performance was evaluated under different operating conditions. The output characteristics of the SFL are sustained regardless of the wavelength and duty cycle of the pump signal. The same laser configuration also allows for clock recovery of input signals, independently of the signal wavelength.
Efficient S-Band Amplification Using Depressed-Cladding Erbium-Doped Silica Fibers
Authors: Rosolem J.B. , Romero M. A.
Published: February 2023

In this paper we review our work to achieve S-band amplification using only erbium doped silica fibers. To this end, double-pass and single pass erbium doped depressed cladding fiber amplifier designed for S band operation are evaluated under changes of the input optical power, pumping power and fiber bending radius. The double pass configuration employs the usual combination of a circulator and a Faraday rotator mirror while the single pass is based on the co-propagating scheme. The amplifiers were characterized in terms of gain and noise figure. It is demonstrated that the double pass topology shows much improved gain performance compared to the single pass configuration although the noise figure is slightly degraded by counter-propagating ASE. Next, the amplifier double pass topology is properly modified to achieve signal amplification simultaneously over S, C and L bands. An embedded dispersion compensating fiber is included and the experimental characterization is carried out in terms gain and noise figure over the CWDM wavelength grid. By providing optical gain to seven CWDM channels spectrally located between 1490 and 1610 nm, the amplifier can extend the reach of a 16-channel CWDM optical bus well beyond the 100 km limit. The system results are then compared to those obtained by using a SOA (semiconductor optical amplifier), under the same experimental conditions.
Recent Advances on Optical Sensing Using Photonic Crystal Fibers
Authors: Marques M. B. , Magalhães F. , Carvalho J. P. , Frazão O. , Araújo F. M. , Santos J. L. , Ferreira L. A.
Published: February 2023

The application of hollow-core photonic crystal fibers for gas sensing is reviewed and discussed. Some problems with splicing to standard fibers and gas diffusion into the core are addressed. Current work at INESC Porto in the development of sensing heads and interrogation units is also reported.
Gaussian Filtering with Tapered Oil-Filled Photonic Bandgap Fibers
Authors: Brunetti A. C. , Scolari L. , Weirich J. , Eskildsen L. , Bellanca G. , Bassi P. , Bjarklev A.
Published: February 2023

A tunable Gaussian filter based on a tapered oil-filled photonic crystal fiber is demonstrated. The filter is centered at λ=1364nm with a bandwidth (FWHM) of 237nm. Tunability is achieved by changing the temperature of the filter. A shift of 210nm of the central wavelength has been observed by increasing the temperature from 25°C to 100°C. The measurements are compared to a simulated spectrum obtained by means of a vectorial Beam Propagation Method model.
Effect of Coupling between Fundamental and Cladding Modes on Bending Losses in Single-Polarization Single-Mode Photonic Crystal Fiber
Authors: Balvedi Gláucia C. , Franco Marcos A. R.
Published: February 2023

In this paper we study the effect of bending on the performance of a single-polarization single-mode (SPSM) photonic crystal fiber previously reported in the literature. The optical fiber consists of a photonic crystal fiber with hexagonal lattice of circular air-holes with an elliptical core formed by eight enlarged holes surrounding the central region of the fiber. Numerical analysis based on full-vector finite element method (VFEM) with a cylindrical perfectly matched layer (PML) was applied to evaluate the bending loss and the confinement loss of the fiber. For the straight fiber only the fundamental slow axis mode (x-polarization) exist because of the very high confinement loss of the fundamental fast axis mode (y-polarization). However, for the bent fiber the fast axis mode and the slow axis mode couple with the gallery of the cladding modes. These coupling prevent the fast axis mode to reach the cutoff. As a consequence, the bending loss curve as a function of the wavelength presents oscillations related with these coupled modes. Our simulations demonstrate that the analyzed fiber does not maintain its single-polarization single-mode characteristics when it is bent with a small curvature radius of 10 mm. However, for a small wavelength range (1.50 pm to 1.53 pm) the fundamental slow axis mode presents values of bending loss lower then 0.1 dB/km while the fast axis mode reach losses of about 150 dB/km, what can be useful for some application.
Simulation Study of Deposition Parameters for Elliptical-Shaped Preforms by VAD for Polarization-Maintaining Fibers
Authors: Fujiwara Eric , Ono Eduardo , Suzuki Carlos K.
Published: February 2023

A novel fabrication method of elliptical-shaped preforms for polarization-maintaining fibers, developed using the VAD technology and based on the variation of the perform rotation velocity from zero to a maximum velocity in repeated cycles of 180°, allows modifying and controlling the preform geometry by choosing the process parameters, such as the maximum rotation velocity and the delay time on zero velocity positions. The effect of each process variable was studied through a mathematical modeling and simulation of the methodology, comprising a simplified model of the soot deposition process. Results demonstrated that preforms with high elllipticity can be obtained by increasing the delay time or decreasing the maximum rotation velocity. It was also observed that the effect of the delay time is more noticeable on the preform geometry than the contribution of maximum velocity. These facts were confirmed when compared to real deposition results, using a VAD chamber with gases fluxes set to 2.33×10-6 m3/s (SiCl4) and 0.8×10-6 m3/s (GeCl4), and setting the burner-target angle to a high deposition rate condition. It is expected that the improvement of the mathematical model can be very useful in order to determine the process conditions necessary to achieve any desired preform geometry, even before the deposition stage.