bluuebunny/crossref_metadata_2025 huggingface dataset:
SPATIAL FREQUENCY RANGE IN THE DETECTION PROCESS—1. NARROW BARS
Authors: Brogan David
Published: December 2007

Abstract— The effect upon the detectability of narrow bars of ideal low‐pass and high‐pass filters was investigated. The results indicate that for optimum detection of the stimulus, spatial frequency components up to about 10 c/deg need to be transmitted. Two models (a multi‐channel model, incorporating probability summation across spatial frequency, and a Grating Sensitivity Curve model) were used in attempting to fit the results. The multi‐channel model provided a more realistic fit, but both models ultimately failed because of non‐linearity in the summation of responses to frequency components.
DISTANCE, DURATION AND BLUR EFFECTS ON THE PERCEPTION OF PSEUDOISOCHROMATIC STIMULI
Authors: Long Gerald M. , Lyman Brian J. , Tuck J. Porter
Published: December 2007

Abstract— Two experiments are reported that examine the effects of viewing distance, viewing duration, and stimulus clarity on performance with three popular versions of the pseudoisochromatic tests of colour deficiency. With a large sample of colour‐normal observers, highly significant effects of these viewing conditions are found. In addition, large differences in sensitivity to these conditions are obtained among the three tests employed (The American Optical Corporation test, the Dvorine test, and the Ishihara test). Results are discussed in terms of practical implications for test administration and in terms of likely processes, in addition to colour discrimination, assessed by these tests.
VERGENCE EYE‐MOVEMENT RESPONSES TO WHOLE‐BODY LINEAR ACCELERATION STIMULI IN MAN*
Authors: Smith Russell
Published: December 2007

Abstract— Eight human subjects were exposed to periodic linear acceleration stimuli of ±1.0 ms‐2 at 0.2 Hz and ±2.5 ms‐2 at 0.3, 0.45 and 0.67 Hz, whilst lying in the supine position on a large‐stroke vertical vibration platform. Eye movements were recorded by an infrared corneal reflection technique. In conditions of total darkness, with no visual stimulation, all subjects exhibited eye‐movement responses composed of both conjugate and vergence components. Subsequent computer analysis of the vergence eye‐movement responses showed that they were periodic and related to subject displacement. In a second experimental condition, a platen‐fixed LED matrix fixation target was illuminated 0.91 m vertically above the subject. It was found that fixation upon this target did not abolish the vergence eye‐movement response, although it was suppressed by ˜50%.
TRANSFORMATION OF SPHERO‐CYLINDERS. I. RANKING PROCEDURE
Authors: Saunders H.
Published: December 2007

Abstract— Parametric statistical analysis requires a rule by which the variates are quantitavely ranked. In this study an isomorphic transformation of sphero‐cylinders is developed and two alternative ranking hierarchies for the sphero‐cylinder are proposed.
THE EFFECT OF VERTICAL DIFFERENTIAL PRISM ON THE BINOCULAR CONTRAST SENSITIVITY FUNCTION
Authors: Tunnacliffe Alan H. , Williams Andrew T.
Published: December 2007

Abstract— The binocular contrast sensitivity function is measured using horizontal sinusoidal gratings with base‐down prism before the right eye. In photopic conditions one prism‐dioptre causes a significant drop in sensitivity at all spatial frequencies and in mesopic conditions as little as a half prism‐dioptre has a similar effect. The implications for a physiological tolerance for unintended vertical differential prism in spectacles are discussed.
AN HISTORICAL REVIEW OF OPTOMETRIC PRINCIPLES AND TECHNIQUES
Authors: Bennett A. G.
Published: December 2007

Abstract‐Beginning with the seventeenth century, when the main scientific foundations were laid, an account is given of the development of various clinical techniques for the assessment of visual acuity and amctropia. Both subjective and objective methods of refraction, with associated instrumentation, are reviewed. Among the more recent techniques described are meridional refraction, astigmatic decomposition, and photorefraction. In various fields, some little known contributions of particular interest are brought to light.
A LONGITUDINAL STUDY OF THE AGE‐DEPENDENCE OF HUMAN OCULAR REFRACTION‐I. AGE‐DEPENDENT CHANGES IN THE EQUIVALENT SPHERE
Authors: Saunders Harold
Published: December 2007

Following on from a cross‐sectional analysis of refraction data (Saunders, 1981), the present paper attempts the evaluation of serial recordings of a new sample of refractive corrections using longitudinal methods. This study compares the results of the cross‐sectional and longitudinal methods, investigates whether or not the latter supports the conclusions of the former, examines to what accuracy this is achieved and, where the results differ, seeks a reason for this. It is demonstrated that in spite of such differences the two methods coincide in their conclusions.
CORNEAL TOPOGRAPHY: A CLINICAL MODEL
Authors: Guillon Michel , Lydon Donald P. M. , Wilson Christine
Published: December 2007

A keratometric photokeratoscopic study of 220 eyes representative of a normal population leads to the ellipsoid corneal model proposed. This model is applicable to the design of rigid corneal lenses and to the calculation of computer models of the dioptric system of the eye. The results obtained show that (1) there is a systematic difference between central keratometric and photokeratoscopic measurements that is statistically but not clinically significant, (2) a significant number of corneas steepen at the periphery, (3) the corneal shape varies greatly with a normal population and (4) peripheral and central astigmatisms are usually similar.
DISPLACEMENT THRESHOLDS FOR CONTINUOUS OSCILLATORY MOVEMENT: THE EFFECT OF OSCILLATION WAVEFORM AND TEMPORAL FREQUENCY
Authors: Buckingham Terry , Whitaker David
Published: December 2007

Abstract— Displacement thresholds for continuous oscillatory movement of a grating, subtending 2 cycle deg‐1, were measured for square‐, triangular‐and sine‐wave oscillation over the frequency range 1–20 Hz. Without reference lines, thresholds were highly dependent upon temporal frequency and oscillation waveform. With reference lines, thresholds were dependent upon oscillation waveform but not frequency. Greatest sensitivity was shown to square‐wave oscillation and least to triangular‐wave. Results are discussed in terms of velocity‐and displacement‐analysing systems. Increasing the spatial frequency of the sinusoidally oscillating grating had little effect on displacement thresholds.
THE EFFECT OF OPTICAL BLUR ON VISUAL ACUITY FOR TARGETS OF DIFFERENT LUMINANCES
Authors: Simpson Trefford L. , Barbeito Raphael , Bedell Harold E.
Published: December 2007

Abstract— We studied the effect of 1.25 D of optical blur on visual acuity at luminances ranging from photopic to low mesopic levels. Optical blur reduces acuity at all luminances tested, this reduction being fourfold at a high photopic level (170 cd m‐2) and twofold in low mesopia (0.017 cd m‐2). The reduction of visual acuity with blur at low luminances is greater than might be expected from a spatial frequency analysis of vision.
CONTRAST SENSITIVITY IN PSEUDOPHAKIA AND APHAKIA
Authors: Weatherill John , Yap Maurice
Published: December 2007

Abstract— Contrast sensitivity was measured in pseudophakic and aphakic patients. No difference could be demonstrated between the contrast sensitivities of patients with anterior chamber/iris‐supported and posterior chamber intraocular lenses (IOLs). Little difference was found between pseudophakics and aphakics. Interocular contrast ratios in five pseudophakic patients with normal fellow eyes revealed a range of contrast attennation characteristics which may be attributed to the IOL and corneal and posterior capsule transmission.
DEFINITIONS FOR HYDRATION CHANGES OF HYDROGEL LENSES
Authors: BrennanM Noel A. , Efron Nathan , Truong Van Tan , Watkins Rodney D.
Published: December 2007

Abstract— Authors of studies on the hydration characteristics of hydrogel lenses have used a variety of definitions to describe the changes observed with exposure of the lenses to different environments. This has resulted in difficulties in the interpretation of published data. In particular, the single term “percentage dehydration” has been used to denote different mathematical expressions for alterations to the lens composition. A detailed theoretical analysis of hydrogel hydration levels is presented to examine definitions for lens hydration changes, compare results obtained under different definitions and propose appropriate usage for the alternative definitions according to the aspect of lens performance under consideration. The interrelationships between the commonly used definitions of dehydration are shown to be independent of initial lens mass but dependent on initial water content. Typically, higher water content lenses undergo considerably larger mass changes than lower water content lenses, an effect that may be masked if these changes are presented as changes of water content. There are a number of clinical consequences of lens dehydration, the importance of which will vary depending on the initial lens water content. It is therefore essential when comparing different water content lenses on the basis of the extent of dehydration to do so with respect to a specific clinical consequence rather than in general terms.
HETEROPHORIA: A VERGENCE ADAPTIVE POSITION*
Authors: Dharamshi) Begumpara Sethi (née
Published: December 2007

Abstracts— Previous experiments have shown that as the adaptive change becomes more complete with prolonged wear of a prism, the adaptive decay during monocular occlusion (MO) becomes slower; at the same time, adaptation to a further prism disparity becomes faster. If phoria is an adapted position of the oculomotor system then, as with prism adaptation, it should demonstrate an adaptive decay during MO. The rate of this decay should be inversely related to the rate of adaptation to a prism. In the first part of the paper, changes in the horizontal and vertical phorias were demonstrated at distance and near during 4 hr of MO. In the second part, adaptation to various prism disparities (horizontal and vertical) was monitored. The rates of adaptation were found to be inversely related to the rates of phoria decay during MO. The phoria position is, therefore, an adapted position of the vergence system.
ASSESSMENT OF TECHNIQUES FOR MEASURING CONTRAST SENSITIVITY IN CHILDREN*
Authors: Brown V. A. , Woodhouse J. M.
Published: December 2007

Abstracts— Contrast sensitivity was measured in 10 children aged from 3 to 11 years using 4 psychophysical techniques in order to establish the best method of measurement for clinical use. Of the four methods, staircase, ascending continuous, modified Von Bekesy and two‐alternate forced‐choice, the staircase was selected as the most appropriate clinical technique and monocular contrast sensitivity functions of normal children were measured.
SEPARATION OF THE REFLECTION BY THE INNER LIMITING MEMBRANE
Authors: Gorrand J.‐M.
Published: December 2007

Abstracts— A ray incident upon the inner limiting membrane is specularly reflected, whereas the other retinal structures reflect light diffusely into large solid angles. Thus by moving a small diaphragm inside the exit pupil, it is possible to separate the component of the reflected light which originates at the inner limiting membrane. To check that this light added to the aerial image is not caused by the specular reflection from an anterior surface (cornea or lens), interference fringes were projected onto the retina, and their modulation depth was measured in the plane conjugate with the retina: since the inner limiting membrane and the anterior media were the sources of modulated and unmodulated aerial images respectively, their contributions could be separately measured.
TWO FACTORS AFFECTING SACCADIC AMPLITUDE DURING VERGENCE: THE LOCATION OF THE CYCLOPEAN EYE AND A LEFT‐RIGHT BIAS
Authors: Barbeito Raphael , Tam Wa James , Ono Hiroshi
Published: December 2007

Abstracts— Saccades occurring during vergence have been reported to differ in amplitude depending on whether the saccade drives the eyes leftward or rightward. Furthermore, this difference varies in degree and direction among individuals. We examined two explanations of the variation—that it is the result of the cyclopean eye being nearer to one eye, and that it is the result of a pervasive bias, within an individual, to make larger saccades either leftward or rightward. Examination of the saccades of 14 subjects, recorded during both divergent and convergent movements that required leftward or rightward saccades, shows that neither explanation alone provides an adequate account of the differences observed. However, statistical analysis (ANOVA) indicates that almost 60% of the total variation in the observed saccadic amplitudes is related to the two explanations taken together. We speculate that both influences act on the saccade in a given individual, and that the amplitude manifested depends on the relative magnitudes of the two influences within that individual.
THE EFFECT OF HORIZONTAL DIFFERENTIAL PRISM ON THE BINOCULAR CONTRAST SENSITIVITY FUNCTION
Authors: Tunnacliffe Alan H. , Williams Andrew T.
Published: December 2007

Abstracts— The photopic binocular contrast sensitivity function is measured using a two‐way resolution choice sinusoidal‐grating target with horizontal differential prism before the right eye of one subject (AHT). A significant drop in sensitivity occurred with 3 prism‐dioptres base‐out or 4 prism‐dioptres base‐in prism at an observation distance of 5.9 m, and with 2 prism‐dioptres base‐out or 8 prism‐dioptres base‐in at 50 cm. An equivalent effect was confirmed with three additional subjects at a test distance of 2 m. The relationship between these results, the passive position, and the fusional reserves is discussed and reference is made to the effect of vertical differential prism.
DIFFERENT RATES AND AMOUNTS OF VISION FUNCTION RECOVERY DURING ORTHOPTIC THERAPY IN AN OLDER STRABISMIC AMBLYOPE
Authors: Hokoda Steven C. , Ciuffreda Kenneth J.
Published: December 2007

Abstracts— Orthoptic therapy was instituted in an 11‐year‐old patient having deep amblyopia, constant small‐angle esotropia with anomalous retinal correspondence, and a past history of minimal success with such therapy. This combination of factors pointed toward a poor prognosis for substantial recovery of vision function. Rate of recovery of several monocular and binocular vision functions was monitored during the course of 18 months of intensive orthoptic therapy. Results showed marked improvement in several monocular vision functions, suggesting presence of considerable residual neural plasticity of multiple sites in the visual pathways of this older amblyope.
CONTRAST SENSITIVITY DURING PROVOKED VISUAL IMPAIRMENT IN MULTIPLE SCLEROSIS*
Authors: Sekuler Robert , Owsley Cynthia , Berenberg Richard
Published: December 2007

Abstracts— Many patients with multiple sclerosis have subjective visual complaints that are intensified by exercise (Uhthoff's symptom). We report a case demonstrating the utility of contrast sensitivity testing in such visual complaints. Contrast sensitivity was measured before and after exercise in a multiple sclerosis patient with Uhthoff's symptom and in two healthy control subjects. A short exercise period reduced the patient's contrast sensitivity for some target sizes, but had no effect on his visual acuity; a longer exercise period produced a greater, more uniform loss of contrast sensitivity and also reduced visual acuity. Contrast sensitivities and visual acuities of the control subjects were not affected by exercise.
CORNEAL THICKNESS AND DIAMETER IN THE DOMESTIC CAT
Authors: Carrington Stephen D. , Woodward E. Geoffrey
Published: December 2007

Abstract— Two sample groups of domestic cats were assessed for (a) central corneal thickness (17 eyes), using optical pachymetry, and (b) horizontal and vertical corneal diameter, using a photographic method (20 eyes). The average corneal thickness was 0.755 _+ 0.33 mm. The mean horizontal diameter was 16.5 ‐/+ 0.60 mm and the mean vertical diameter was 16.2 2‐/+ 0.61 mm. The horizontal corneal diameter was significantly greater than the vertical corneal diameter (p < 0.001, paired t test).
Comparison of Wesson and modified Sheedy fixation disparity tests. Do fixation disparity measures relate to normal binocular status?
Authors: van Haeringen R. , McClurg P. , Cameron K. D.
Published: December 2007

Abstract— A new fixation disparity measuring device, the Wesson Fixation Disparity Card, is compared with the modified Sheedy Disparometer. Twenty‐eight subjects were divided into normal and abnormal categories of binocular status determined by clascical clinical techniques rather than on patients' subjective symptomatology. Fixation disparity curves were generated on all subjects using both instruments. There were significant differences between the two instruments. Neither instrument was able to distinguish between normal and abnormal subjects but, over a five day period, each instrument produced repeatable results. The validity of fixation disparity measurements using either instrument on naive observers, especially children, is questioned.
THE CORTICAL REPRESENTATION OF GRADIENT‐ADAPTED MULTIPLE‐STIMULUS PERIMETRY
Authors: Wild J. M. , Wood J. M. , Barnes D. A.
Published: December 2007

Abstract— Some stimuli, if scaled in proportion to the reciprocal of inter ganglion cell receptive field separation (M‐scaled) exhibit an isosensitivity profile. Perimetric profiles which are isosensitive across the extent of the normal visual field facilitate multiple stimulus perimetry and provide a convenient method for the detection of abnormality. The purpose of the investigation was to establish whether the stimulus diameters necessary to produce an isosensitive perimetric profile were scaled in proportion to M. Sensitivity profiles for a sample of 15 age‐matched observers were obtained with the Friedmann VFA Mk II. The stimulus aperture diameters were then measured under 100 x magnification. The observed elliptical apertures, corrected for obliquity of viewing, plate thickness and distance from the eye were represented as diameters of circles possessing an equivalent area to that of the ellipse. The apparent diameters were then M‐scaled relative to stimulus pattern h using the equations of Rovamo and Virsu (1979). An overestimation of the M‐scaled diameters relative to the apparent diameters was noted which increased with eccentricity for all four cardinal meridians by a factor of up to 3.5 times. It is suggested that the over compensation indicates that the cortical representation of perimetric spot targets at low photopic adaptation levels depends not only upon retinal ganglion cell density but also upon the variation of ganglion cell characteristics with eccentricity. The implications of this finding for perimetric instrument design are discussed.
A NEW PHOTOGRAPHIC‐BASED SYSTEM FOR THE MEASUREMENT OF CONTRAST SENSITIVITY
Authors: Barbur John L. , Hoban Barbara , Thomson David
Published: December 2007

Abstract— A new photographic‐based system has been developed for the measurement of contrast sensitivity in human vision. The system has several advantages over other photographic methods and is relatively easy and inexpensive to produce. This paper describes the design of the new system and the methods used in the production of the photographic prints. Preliminary tests show that full contrast sensitivity curves can be obtained with a small number of photographic prints and that these curves are very similar to those obtained using a carefully calibrated electronic pattern generator.
THE EFFECT OF SPATIAL FREQUENCY ON STEADY‐STATE ACCOMMODATION
Authors: Ward P. A.
Published: December 2007

Abstract— Accommodation responses to sinusoidally modulated vertical gratings, at a vergence of ‐5.0 D, were measured over a 10 min period. Three spatial frequencies were employed: 1.67, 5.0 and 15 cycles degree‐1. The results show that 1.67 and 5.0 cycles degree‐1 elicit good accommodation responses which are temporally stable. All five subjects employed were unable to maintain an accurate accommodation response to a 15 cycles degree‐1 grating. Consideration of the changes occurring in the retinal modulation with accommodative error indicates that spatial frequencies around 5.0 cycles degree‐1 are the most useful for accommodation.
EFFECTS OF RELAXATION AND AVERSIVE VISUAL STIMULATION ON DARK FOCUS ACCOMMODATION
Authors: Miller R. J. , Takahama Masatoshi
Published: December 2007

Abstract— There is evidence that sympathetic innervation induces decreases in accommodation or accommodation amplitude. If so, emotional stress that produces sympathetic activation should induce similar changes in accommodation. In two experiments, dark focus accommodation was assessed following deep relaxation and after subjects looked at gruesome slides. Results showed that stress exposure led to lower dark focus values than did relaxation. Further, the degree to which dark focus was affected depended on subjects' levels of perceived arousal, and on the degree of stressfulness represented by the slides. It was concluded that psychological stress can produce predictable changes in accommodation, changes most parsimoniously understood in terms of autonomic innervation of the ciliary body.
EFFECT OF A NEAR‐VISION TASK ON THE RESPONSE AC/A OF A MYOPIC POPULATION
Authors: Rosenfield Mark , Gilmartin Bernard
Published: December 2007

Abstract— The effect of a 14 minute near‐vision task on the response accommodative convergence/accommodation (AC/A) ratio was investigated for three refractive groups (each comprising N= 17)—emmetropes, early‐onset myopes (EOM), i.e. myopia onset prior to 15 years of age, and late‐onset myopes (LOM), i.e. onset 15 years or later. AC/A ratios were derived from accommodative stimuli of 3.0, 3.9 and 4.6 D. Accommodation was measured using an objective infra‐red autorefractor which allowed unrestricted viewing through a semi‐silvered mirror and this permitted concomitant vergence changes to be assessed using a Maddox rod and tangent scale. EOMs exhibit a significantly higher response AC/A ratio than the two other refractive groups. The implications of these modifications in response AC/A are discussed with reference to current models of accommodation‐vergence interaction.
SCHEMATIC MODELLING OF PERIPHERAL ASTIGMATISM IN REAL EYES
Authors: Dunne M. C. M. , Barnes D. A.
Published: December 2007

Abstract— A method is described whereby any schematic eye possessing a two‐surfaced, monoindicial lens can be manipulated to yield the same amounts of peripheral astigmatism as found in real eyes. Its optical performance is discussed and it is demonstrated that schematic eyes of this type cannot simultaneously yield the amounts of peripheral astigmatism and spherical aberration that are observed in real eyes.
UNCORRECTED REFRACTIVE ERROR AMONG A HOSPITAL POPULATION
Authors: Evans Kevin
Published: December 2007

Abstract— Patients admitted for general medical care to a North London Hospital were screened using a pinhole disc in conjunction with their usual visual aid. One third of the group showed significant improvement in visual acuity, suggesting a change in refractive correction was necessary. These people were not more likely to have had less recent eye examinations or to complain of poor vision. They were more likely to be over 50 years old, have poor mobility, to have no idea of cost of change in refractive correction and to subjectively note improvement in vision with pinhole disc.
A “HIDDEN” DEFICIT IN CENTRAL VISION IN DIABETIC PAN‐RETINAL PHOTOCOAGULATION PATIENTS
Authors: Russell Phillip , Sekuler Robert , Fikre John
Published: December 2007

Abstract— Adaptation ability in the center of vision was tested in diabetic patients treated with pan‐retinal photocoagulation for diabetic retinopathy and in normal control subjects. This was accomplished with a specially designed contrast sensitivity testing regimen. Patients with retinopathy showed “hidden” deficits, losses in adaptation ability that could not be measured by standard clinical tests, such as visual acuity. This new test thus quantifies a previously unmeasured visual problem that affects the everyday visual function of these patients.
AN AVERAGING METHOD FOR THE INTERPRETATION OF THE FARNSWORTH‐MUNSELL 100‐HUE TEST—I. CONGENITAL COLOUR VISION DEFECTS
Authors: Dain S. J. , Birch Jennifer
Published: December 2007

Abstract— A method is described for identifying polarity in Farnsworth‐Munsell 100‐Hue test data. The method is facilitated by the use of a micro‐computer and involves the plotting of “averaged” scores for each cap of the test. Results are presented for 30 protanopes, 30 deuteranopes, 1 tritanope and 2 typical rod monochromats. Analysis of the results shows that the proposed technique is compatible with standard methods of interpreting 100‐Hue plots and is suitable to use when error scores are high and when polarity is difficult to interpret.
OBJECT‐MOTION DETECTION AFFECTED BY CONCURRENT SELF‐MOTION PERCEPTION: APPLIED ASPECTS FOR VEHICLE GUIDANCE
Authors: Probst Thomas , Krafczyk Siegbert , Brandt Thomas
Published: December 2007

Abstract— Thresholds and response times for object‐motion detection are significantly raised during concurrent real or visually induced self‐motion perception. This was demonstrated by standardized laboratory experiments in which subjects had to react to a suprathreshold visual stimulus (1°‐light spot moving with 5°/s speed) under different stimulus conditions of simultaneously perceived self‐motion. Elevated response times (mean elevation factor: 3.27) were also obtained for the detection of changes in inter‐vehicle distance (headway) under real road conditions with the simultaneous involvement of self‐and object‐motion perception compared to a corresponding (object‐motion perception) simulation in the laboratory without any self‐motion. With regard to vehicle guidance, existing concepts of safe stopping distances, which depend upon adequate detection of a collision course and the corresponding reaction times, have to be recalculated.
POWER SPECTRUM ANALYSIS IN THE STUDY OF OCULAR MECHANISMS
Authors: Pugh J. R. , Eadie A. S. , Winn B. , Heron G.
Published: December 2007

Abstract— The use of power‐spectrum analysis in the study of ocular dynamics is becoming increasingly widespread. This paper summarizes the key points of signal acquisition and power‐spectrum analysis, emphasizing aspects which we have found to be of relevance when the technique is applied to experiments in binocular accommodation. The considerations and conclusions are relevant to other areas of investigation into ocular dynamics and similar biological systems.
F‐M 100‐HUE TOTAL ERROR SCORES HAVE DISCRETE VALUES
Authors: Dain S. J. , Saunders J. E.
Published: December 2007

Abstract— A proof is presented which shows that the total error scores derived from the Farnsworth‐Munsell 100‐Hue test are an integer multiple of 4. The one proviso for this relates to the way in which the first and last caps in a box are handled.
COMPUTER PROCESSING OF OCULAR PHOTOGRAPHS—A REVIEW*
Authors: Gilchrist Jim
Published: December 2007

Abstract— The use of digital image processing for enhancement and analysis of ocular photographs is a growing field of clinical research and application. The value of ocular image analysis and the requirements for acquisition and storage of digital images are outlined. A number of techniques for image enhancement and analysis are introduced, and their applications to lens and fundus images are reviewed.
PSYCHOPHYSICAL MEASUREMENT OF THE FOVEAL AVASCULAR ZONE*
Authors: Yap Maurice , Gilchrist Jim , Weatherill John
Published: December 2007

Abstract— The size of the foveal avascular zone (FAZ) reflects the condition of the microcapillary circulation in the foveal area. A number of studies have shown a significant increase in FAZ size in conditions of vascular pathology including diabetes. A non‐invasive method of estimating FAZ size may be a valuable addition to a psychophysical test battery. We used a blue‐light field to reveal the activity of the retinal leucocytes to two groups of normal subjects with average ages 24 and 61 years. Two methods were used to estimate the FAZ size, making use of the fact that subjects could see their own FAZ as the area free of leucocyte activity. The first method required subjects to indicate when leucocyte activity stopped as the field size was decreased and when it reappeared as field size was increased. The second required subjects to match the size of the leucocyte‐free area with a white circle superimposed on the field. A search algorithm was used to change circle size according to subjects' responses. Results show a significant difference in FAZ size between the two age groups with both methods of measurement, and estimates were comparable to those reported using angiographic methods.
CLINICAL USE OF DIAGNOSTIC TESTS*
Authors: McClure Elizabeth A.
Published: December 2007

Abstract— Case histories are presented to illustrate a cross‐section of work undertaken by optometrists in the Visual Assessment Department at the Tennent Institute of Ophthalmology. The clinical value of ocular diagnostic tests is emphasized, with particular reference to the differential diagnosis in cases of optic atrophy.
THE APPLICATION OF A COMPREHENSIVE VISUAL SCREENING PROGRAMME TO CHILDREN AGED 3–5 YEARS. CAN A MODIFIED PROCEDURE BE DEVISED FOR VISUAL SCREENING BY ANCILLARY STAFF?
Authors: Dholakia S.
Published: December 2007

Abstract— Current commercially available tests to examine visual performance in children are discussed and adapted for a visual screening programme applied to 249 children aged 3–5 years at school or playgroup premises. Correlation of refractive and ocular muscle findings with the remaining tests is evaluated. A simplified screening procedure is thereby recommended which may be undertaken by ancillary staff, without any need for sophisticated equipment. This would enable identification, for further examination, of most children whose refraction and eye coordination are outside normal limits.
THE CHROMATIC ABERRATION ADJUSTMENT IN LASER OPTOMETRY
Authors: Miller R. J.
Published: December 2007

Abstract— The issues involved in designing chromatic aberration corrections in laser optometry are reviewed. There is considerable disagreement regarding both the magnitude of human eye chromatic aberration and the value that should be assumed for the reference wavelength. Also important are the observer's accommodative state, target luminance wavelength, laser wavelength, intersubject dioptric variations, and several other factors. The appropriate solution for most experiments appears to be to report no chromatic aberration adjustment at all; rather, the investigator should provide basic technical information from which interested readers can make their own corrections, depending on the assumptions of importance to them.
VARIATION OF SACCADIC SUPPRESSION WITH TARGET ECCENTRICITY
Authors: Osaka Naoyuki
Published: December 2007

Abstract— Two LEDs separated by 24° from each other were employed as saccadic fixation sources located on a circle about the centre of the saccade path. Either horizontal, vertical or oblique saccade paths were used and a brief test flash was presented at one of five retinal eccentricities during each saccade. The percentage of detected flashes was measured as a function of the location of the test stimulus and of its time delay with respect to the onset of the saccade. The results suggest that saccadic suppression is maximal at the fovea and is significantly decreased as retinal eccentricity increases.

Based on a paper presented at the 2nd European Conference on Eye Movements held at Nottingham, U.K. and supported in part by the Japanese Ministry of Education Grant #56510078 and the Yoshida Memorial Foundation Grant 17–9.
THE INFLUENCE OF TEMPORAL FREQUENCY AND WAVELENGTH ON BETA MOVEMENT
Authors: Buckingham Terry
Published: December 2007

Abstract—The maximum displacement threshold for beta (apparent) movement was determined using small near‐monochromatic stimuli subtending 2 min arc, over the frequency range 1.67–6.67 Hz. Displacement thresholds for the apparently oscillating spot were dependent upon both temporal frequency (F(9,903)= 1413) and wavelength (F(12,903)= 19.6), the stimuli having been equated for luminance. Significant interaction effects (F(108,903)= 3.32) demonstrated that the influence of colour varied with temporal frequency. It is suggested that short‐range apparent movement over this frequency range may be mediated by a mechanism which is colour dependent.
A QUANTITATIVE INVESTIGATION INTO THE EFFECTS OF PUPIL DIAMETER AND DEFOCUS ON CONTRAST SENSITIVITY FOR AN EXTENDED RANGE OF SPATIAL FREQUENCIES IN NATURAL AND HOMATROPINIZED EYES
Authors: Kay C. D. , Morrison J. D.
Published: December 2007

Abstract—Contrast sensitivity was measured in 12 subjects for different spatial frequencies of sinusoidal grating patterns, generated by oscilloscope, for pupil diameters 2–8 mm and for defocus of +1–4 D, following homatropine eyedrops. Changes in pupil diameter, without correction for the change in retinal illumination, had no significant effect on contrast sensitivity, except at 0.5 and 1 c deg‐1 when a significant reduction occurred with the 2 mm pupil. Defocus caused a large reduction in contrast sensitivity at spatial frequencies higher than the peak of the contrast sensitivity function (3 c deg‐1) and a smaller reduction below the peak. In both individual and group results, there was no significant effect of defocus in causing a disproportionately greater reduction in contrast sensitivity at higher spatial frequencies nor were the zero mimina predicted by optical theory observed. The results were confirmed in eight subjects viewing with the natural eye, though the reduction in contrast sensitivity caused by + 1 D defocus was not significant: this was attributed to the relaxation of accommodation in response to defocus. To predict the performance of the visual system, multiple regression equations were derived to incorporate terms for pupil diameter, defocus and spatial frequency. These equations reflected the lack of effect of pupil diameter, while defocus caused a 51% loss in contrast sensitivity per dioptre at higher spatial frequencies (3–38 c deg‐1) and a 19% reduction at low spatial frequencies.
STRUCTURE OF THE TEAR FILM DURING THE BLINKING PROCESS
Authors: Forst Günter
Published: December 2007

Abstract—The structure of the tear film was photographed immediately prior and subsequent to lid closure with a magnification factor of 140 ×. Deformations of the tear film were observed in the form of “creasing”, “wave motion” and also “fairly rough graininess” which point to a remarkably stable consistency of the lipid layer.
WORLD OPTOMETRY
Authors: Pickwell David
Published: December 2007

Abstract The International Optometric and Optical League (IOOL) sent out a questionnaire to contacts in countries across the world in order to formulate an “Optometry Profile” on as many countries as possible. The information from the 58 replies is summarized. The very varied distribution of optometric services that is revealed is discussed in the light of experience gained by the author in his own visits and correspondence relating to the worldwide situation of optometry.
OCULOMOTOR CONSEQUENCES OF BETA‐ADRENOCEPTOR ANTAGONISM DURING SUSTAINED NEAR VISION
Authors: Rosenfield Mark , Gilmartin Bernard
Published: December 2007

Abstract The effect of a topical non‐selective beta‐adrenergic antagonist, timolol maleate (0.5%) on the response accommodative convergence/accommodation (AC/A) ratio was monitored during a 16 min near‐vision task. A double‐blind protocol was adopted between timolol and a saline control for 17 emmetropic subjects. Timolol produced a significant reduction in AC/A during the first 4 min of the task with respect to saline. This reduction was mediated via accommodative convergence and it is proposed that this demonstrates direct involvement of sympathetic innervation to the ciliary muscle during the initial stages of a near‐vision task.
A SCHEMATIC EYE MODEL FOR THE EFFECTS OF TRANSLATION AND ROTATION OF OCULAR COMPONENTS ON PERIPHERAL ASTIGMATISM
Authors: Barnes D. A. , Dunne M. C. M. , Clement R. A.
Published: December 2007

Abstract The relative contributions of translation and rotation of the cornea and lens to peripheral astigmatic asymmetry have been investigated using a linear algebraic ray tracing method. It is believed that lenticular rotation is responsible for angle alpha, so bringing about peripheral astigmatic asymmetry, as normally occurs in human eyes over the temporal and nasal retina. Rotation of the cornea may be responsible for the small numbers of eyes which exhibit large amounts of peripheral astigmatic asymmetry. The effects of corneal rotation and translation on the dimensions of the entrance pupil are illustrated.
THE PHYSIOLOGICAL BASIS FOR THE SENSATION OF GLOOM: QUANTITATIVE AND QUALITATIVE ASPECTS
Authors: Rothwell Susan E. , Campbell Fergus W.
Published: December 2007

Abstract As our ambient lighting is gradually reduced from a high level, subjects use the following words‐bright, gloomy, dim and dark. On six subjects the light level at which these decisions are given has been measured. It has been found that the word gloomy is used when the rods begin to take over from the colour‐sensitive daylight cones.
THE ORTHOPHORIZATION OF HETEROPHORIA
Authors: Dowley D.
Published: December 2007

Abstract The distribution of heterophoria within the general population is significantly non‐normal and a high incidence of approximate orthophoria is observed. This observation has been named the orthophorization of heterophoria. It has been suggested that prism adaptation is the mechanism underlying orthophorization. A prolonged occlusion experiment has been used to investigate this possibility and further supports this theory.
Test—retest reliability of the Arden Grating Test: inter‐tester variability
Authors: Reeves B. C. , Hill A. R. , Ross J. E.
Published: December 2007

The aim of this study was to investigate the test‐retest reliability of the Arden Grating Test (AGT), and to assess the extent to which any variance in AGT score on retest can be attributed to intra‐subject and inter‐tester differences. Twelve patients with various patholgies and whose contrast sensitivity covered a wide range were each tested twice by six testers. It was shown that variance attributable to testing by different clinicians accounted for approximately 25% of the total variance, and that the 95% confidence limits about any observed score were ± 15 AGT units, which is about one quarter of the total dynamic range of the test. The large range of scores encompassed by the 95 % confidence limits represents considerable unreliability, the consequence of which is a high misclassification rate, i.e. many false positives and false negatives, especially in the context of primary vision screening for which it was designed.
Fluctuations in accommodation: a review
Authors: Charman W.N. , Heron G.
Published: December 2007

When a young observer attempts to accommodate steadily on a fixed stimulus, the norminally steady‐state response shows small instabilities or fluctuations (sometimes termed microfluctuations or oscillations). These fluctuations typically have an amplitude of a few tenths of a dioptre and a frequency spectrum extending up to a few Hertz. The properties of these fluctuations are described for various viewing conditions: pupil diameter, target vergence, target form, target contrast, and target luminance all influence the frequency spectra of the oscillations, as may anomalies of vision such as amblyopia. The possible roles that the fluctuations might play in the function of the accommodative system are discussed. It is suggested that the higher frequency components around 2 Hz may arise from the mechanical and elastic characteristics of the lens, zonule and ciliary body. Components at lower frequencies (<0.5 Hz) may be of more significance in the function of the accommodative control system.
Mean response and oscillations of accommodation for various stimulus vergences in relation to accommodation feedback control
Authors: Miege C. , Denieul P.
Published: December 2007

Mean responses and fluctuations of accommodation were recorded by means of a high‐sensitivity infra‐red optometer over a large dioptric range (+3 to ‐9 D) We found that both the effective absoulute amplitude and the 2 Hz relative activity of fluctuations of accommodation exhibit a maximum within the ‐1 to ‐4 D range of stimulus vergence for which the focus error (lag of accommodation) is minimal, whereas no activity is observed at the subject's near and far points. But the 2 Hz relative activity of accommodative fluctuations provides a better description of the control; this parameter was found to be positively correlated with the sensitivity of the accommodative system to defocus blur (input of the feedback loop), providing support for the active role of these fluctuations in the accommodative system.
Difictive colour vision can impede information acquisition form redundantly colour‐Coded video displays
Authors: Cole B. L. , Macdonald W. A.
Published: December 2007

Earlier findings showed that redundant colour coding decreased response times and reduced errors in carrying out various tasks that required information acquisition from the video desplay of an electronic flight instrument system. The results of this experiment showed that observers with defective colour vision have slower response times and higher error rates than normal observers for some of the tasks and that their performance is similar to that of colour‐normal observrers for a monochrome display. Howerver, they were not disadvantaged when blue was used to colour code thae target feature. Protanopes were shown to be especiall disadvantaged in responding to a red ‘fail’ message.
Amplitude variability of the transient visual evoked response
Authors: Douthwaite W. A. , Jenkins T. C. A.
Published: December 2007

The amplitude repeatability of pattern reversal visual evoked response using a 5.5 and 40′ arc check was investigated in twelve subjects with each subject recording ten 64 sweep runs. The variability by visual inspection or by analysis of variance suggests that a single run will provide a representative amplitude for a 40′ are check whereas the 5.5′ check will require more runs merged together before the amplitude is stable. The larger spread of error encountered with the 40′ are check may point to a visual component contributing to more amplitude variability. The possibility of making some assessment of the level of noise present during recording is discussed.
Fluctuations in intra‐ocular pressure with sleep:
Authors: Brown Brian , Burton Paul , Mann Stanley , Parisi Anthony
Published: December 2007

Intra‐ocular pressure (IOP) was measured immediately after normal subjects were woken from at least 5 hours sleep. Measurements were made at approximately 15 s intervals, for about 20 minutes. The IOP of all 14 subjects was elevated after sleep and returned to baseline levels with a time course which was approximately exponential; the longest time constant of return of IOP to baseline was 1056.9 s, and the shortest 133.5 s. Mean time constant of recovery was 404.8 s. The decrease in IOP may be related to melatonin levels which increase during sleep and decrease in the light, or be related to accommodation and eye movements which may act to ‘pump’ aqueous from the eye.
Clinical experience with preferential looking acuity tests in infants and young children
Authors: Thompson Caroline , Drasdo Neville
Published: December 2007

Early prerferential looking methods for the assessment of infant visual acuity relied upon formal psychophysical procedures that were lengthy and only easily applicable to laboratory studies. Two clinically appropriate techniques evaluted in this study both maintain a forced‐choice testing protocol and are administered by a single examiner. One method employs a specially constructed optical projection system to present gratings in a dark‐room. The second method relies upon a relies upon a commercially available acuity card test, used with good room lighting. Paediatric clinical patients and normal infants and young children were examined using both techniques. Findings demonstrate that suitably adapted preferential looking methods can provide rapid and valid estimates of visual acuity in infants and young children. The tests appear sufficiently robust to be appropriate for routine clinical use.
Visual search with non‐foveal vision
Authors: Murphy K. St. J. , Foley‐Fisher J. A.
Published: December 2007

Experiments have been carried out to determine free visual search capabilities when an observer uses only peripheral vision. Foveal vision was eliminated by simulating a full foveal scotoma by means of a stabilized retinal image. Observers were asked to search an unstructured field for a single static target. Results from these experiments established that foveal vision plays a more significant role than is generally assumed in even the most basic of search tasks where the primary mechanism for target acquisition is assumed to be detection only. Results are discussed in terms of the visual lobes for the targets of search.
A novel high‐frequency visual acuity chart
Authors: Medina A. , Howland B.
Published: December 2007

A high‐frequency eye test chart using letters or figures of alternating black and white stripes (or dots) on a grey background was developed. Any cross‐section of the letters has a Fourier transform with a zero frequency component equal to the luminance of the grey background. When the letters are out of focus, their image on the retina fades rapidly into the grey background, rendering them invisible rather than merely blurred as in a standard chart. The chart was calibrated by simulating refractive errors with defocusing lenses applied to a photographic camera and to subjects' eyes. No constant ratio was found between the size of the Snellen letters and the size of the high‐frequency letters for equal visibility. The new chart requires letters for 20/200 acuity to be only 3.6 times larger than those for 20/20 vision. Results confirm the arbitrary nature of the Snellen fraction and warn about the accuracy of visual acuity determined by using charts of different letter types, calibrated by Snellen's system.
Factors affecting the normal perimetric profile derived by automated static threshold LED perimetry
Authors: Wood J.M. , Bullimore M.A. , Wild J.M. , Gilmartin B.
Published: December 2007

The relationship between accommodative fluctuations and perimetric sensitivity was investigated in a group of 10 clinically normal emmetropic subjects using the Dicon AP3000 computer‐assisted perimeter at a bowl luminance of 10 asb. Accommodative microfluctuations were attenuated with the antimuscarinic drug cyclopentolate HCL 1% and the concomitant mydriasis was matched on a separate trial using the sympathomimetic phenylephrine HCI 10%. Saline 0.9% was used as the control. Accommodative microfluctuations were found to play a minor role in determining the magnitude of sensitivity out to an eccentricity of 50; between 50and 27.50, the effect of microfluctuations was masked by the mydriasis produced by the drugs used in the study. The range of sensitivity values at a given location were reduced when accommodative fluctuations were minimized.