bluuebunny/crossref_metadata_2025 huggingface dataset:
ANALYSIS OF REACTION TIMES TO COLOURED STIMULI
Authors: Kranda K.
Published: December 2007

Abstract Reaction times were measured for 10‐and 500‐ms coloured stimuli at three different threshold intensity levels. The stimulus intensity of a 1° foveal flash detected with a probability of 0.5 was taken as the threshold intensity level. All flashes were superimposed on a 1000‐td white background. The reaction time distributions were classified in terms of sustained‐and transient‐like responses. The distributions for the 0.5‐s blue, red and white flashes all appear sustained‐like at the subthreshold and threshold intensity levels. As the blue, red and white flashes were probably detected by different systems (colour‐opponent and luminance) it appears that the sustained‐like response is not a prerogative of any particular detection system. The responses to the blue flashes are on average about 80 ms longer than those to the white and red flashes. This difference can be attributed to a somewhat slower operation of either the blue‐sensitive cones or of the blue/yellow opponent system. The responses to the white 10‐ms flashes are about 120 ms faster than those to the 500‐ms flashes. This considerable difference may reflect the faster response of the transient system.
INFORMATION CONCERNING COLOUR DERIVED FROM A SINGLE BOUNDARY
Authors: Ditchburn R. W. , Foley‐Fisher J. A.
Published: December 2007

Abstract Two experiments are described in which visual information is derived from a single moving boundary in the retinal image, all other boundaries being stabilized so that they contribute no visual information. In this situation the subject perceives the same colours on the two sides of the boundary as would be perceived in normal vision when, owing to eye‐movements, all boundaries in the retinal image are moving relative to the retina. Thus complete information leading to perception of hue and saturation as well as brightness, and not merely differences of hue etc. on the two sides, can be derived from a single boundary.
HUMAN TEAR VOLUME, QUALITY AND EVAPORATION: A COMPARISON OF SCHIRMER, TEAR BREAK‐UP TIME AND RESISTANCE HYGROMETRY TECHNIQUES
Authors: Cedarstaff Thomas H. , Tomlinson Alan
Published: December 2007

Abstract A group of 10 subjects had their tears evaluated by the Schirmer and tear break‐up time (TBUT) tests and their rate of tear evaporation measured by resistance hygrometry. No significant relation was found between the evaporation of the tears and the results obtained by either the Schirmer or the TBUT test. No correlation was found between the Schirmer and the TBUT test results. A significant increase in tear evaporation rate was however produced by the instillation of fluorescein during the TBUT test and by the application of Schirmer strips during the Schirmer test. It is concluded that the Schirmer and TBUT tests measure different features of the tears and these features are not related to the rate of tear evaporation.
SPHERICAL ABERRATION OF THE LENS OF THE GROUND SQUIRREL (SPERMOPHILIS TRIDECEMLINEATUS)
Authors: Sivak J. G. , Gur M. , Dovrat A.
Published: December 2007

Abstract Spherical aberration of the excised ground squirrel lens was measured by photographing the variation in back vertex distance for parallel helium‐neon laser beams of various separations. The results indicate high levels of negative spherical aberration in amounts similar to that measured earlier for the rat lens. The effect of the aberration on resolution ability is likely minimized by the small size of the ground squirrel pupil in diurnal conditions and possibly by the existence of positive corneal aberration.
PHYSIOLOGICAL EXOPHORIA
Authors: Freier Bronwyn E. , Pickwell L. D.
Published: December 2007

Abstract The evidence for the existence, nature and degree of physiological exophoria was examined with respect to a sample of 663 optometric patients. It was found that the mean value for heterophoria is the same for distance and near vision up to the age of the early twenties. After this age, the mean value for distance heterophoria remains unchanged throughout life whilst there is a change in the value for near vision towards exophoria, giving 5 A physiological exophoria. No differences between males and females were found. Physiological exophoria is shown to increase regularly with age and no sudden increase was found at the age when presbyopic additions were first worn. It is concluded that presbyopic additions are not the cause of the physiological exophoria.
SOME ASPECTS OF AMBLYOPIA*
Authors: JENKINS T. C. A.
Published: December 2007

Abstract Some of the recently suggested methods for treating amblyopes are reviewed. A survey of the success rate in 50 young amblyopes, using conventional methods, is described. Whilst 26% did not improve at all in visual acuity, 50% improved by at least two Snellen lines. The suggestion is made that the success rate in the clinic described is similar to that found elsewhere.
WHAT CAN COLOUR THRESHOLDS TELL US ABOUT THE NATURE OF THE UNDERLYING DETECTION MECHANISMS?*
Authors: Kranda K. , King‐Smith P. E.
Published: December 2007

Abstract Two‐colour increment thresholds, which have traditionally been analysed in terms of it‐mechanisms, were subjected here to a different form of analysis. Detection thresholds were measured for monochromatic lest flashes and 10 bichromatic mixture combinations containing various proportions of two out of the five primaries: white, blue, green, yellow and red. The 1° 0.5‐s duration, foveal flasfw appeared on a 1000‐td blue background. All the thresholds were simultaneously filled by asiuming probability summation from a limited number of independent linear mechanisms. The assumption of two detection mechanisms provided a reasonable Tit for all the bichromaiic mixture thresholds. One mechanism received a positive contribution from both M and 1. cone types, whereas the other received an excitatory contribution from the 1. cone type, and an inhibitory contribution from the M cone type. The predictive power of the model was tested and compared to the it‐mechanism concept by fitting a spearal‐sensitivity curve measured under identical conditions. Jt was concluded that parts of II‐mechanism curves probably reflect the responses of colour‐opponent processes rather than those of single cone types.
CONVERGENCE INSUFFICIENCY IN PATIENTS TAKING MEDICINES
Authors: Pickwell L. D. , Hampshire R.
Published: December 2007

Abstract The incidence of convergence insufficiency in patients taking medicines is compared with its incidence in patients taking no therapeutic drugs, in a sample of 648 taken from a normal optometric practice. It is found that the incidence was significantly higher in those patients on medicines considering the group as a whole, h is also found to be higher in older patients, and that most of the older patients were taking medicines whilst the younger patients were not. However, the increase in the incidence of convergence insufficiency in the older patients taking medicines was disproportionately high. It is concluded I hat age is not the only factor in the increased incidence, and that the taking of medicines as a possible indicator of poor general health, is also an important factor in the cause of convergence difficulties.
COST EFFECTIVENESS IN A HOSPITAL CONTACT LENS DEPARTMENT
Authors: Woodward E. G. , Drummond M. F.
Published: December 2007

Abstract Given the shortage of resources in the NHS clinicians are increasingly being asked to search for more cost effective Treatment strategies. This requires consideration not only of the cosi consequences to the NHS but also the impact on quality of care and parents costs. This paper reports two studies of the cost effectiveness of alternative practices within a contact lens department. They show that, for the hospital concerned, both the internal production of, and more extensive stocking of, lenses are cost‐effective strategies. Moreover H is argued that cost ‐ effectiveness analysis might have wider applications within ophthalmology as a whole.
THE ASTIGMATIC MODULUS AND ITS AGE‐DEPENDENCE
Authors: Saunders Harold
Published: December 2007

Abstract The question is posed as to why the modulus of the astigmatic vector appears lo be randomly distributed with age. This paper investigates astigmatic population distributions. On the assumption of statistical independence, the expected probabilities arc determined and compared with the observed values. Measures of central location arc examined so as to determine skew distributions. A correlation is sought between the spherical and the astigmatic components of refractive corrections. It is concluded that the modulus is age‐dependent but that the variations that occur across the age groups are smaller than can be measured by clinical routines.
ACCOMMODATIVE DISFACILITY PRESENTING AS INTERMITTENT EXOTROPIA
Authors: Stark Lawrence , Ciuffreda Kenneth J. , Grisham J. David , Kenyon Robert V. , Liu John , Polse Kenneth
Published: December 2007

Abstract Accommodative disfacility and intermittent exotropia are two common clinically‐observed ocular abnormalities. However, records of individual system dynamics arc rare and mechanisms for possible interactive effects between the accommodation and the vergence system remain obscure in cases of system dysfunction. We present objective, quantitative, static and dynamic records of accommodation, vergence and related system responses in a symptomatic patient having accommodation disfacility and intermittent exotropia and propose that these two conditions worked in a pathogenic symbiotic manner.
ASTIGMATIC DECOMPOSITION: AN ALTERNATIVE SUBJECTIVE REFRACTION TEST EMPLOYING CONVENTIONAL INSTRUMENTATION
Authors: Barnes D. A.
Published: December 2007

Abstract The Humphrey Vision Analyser introduced the refractive technique of astigmatic decomposition with the aid of Alvarez continuously variable sphere‐cylinder lenses. The adaptation of astigmatic decomposition to conventional trial lens systems and a Stokes'lens is described. Refractive errors measured by this technique and by crossed cylinder are compared in 33 optometric patients (one eye each) to assess the relative validity of the method, which compares well with data published on the Humphrey Vision Analyser. Astigmatic decomposition can be considered as an alternative subjective refraction test to more conventional methods.
MEASUREMENT OF THE AXIAL WAVEFRONT ABERRATION OF THE HUMAN EYE
Authors: Walsh G. , Charman W. N.
Published: December 2007

Abstract— An objective variation of Howland and Howland's subjective crossed‐cylinder aberroscope method of estimating ocular aberration is described. An ophthalmoscopic arrangement allows the distorted retinal image of the aberroscope grid to be directly photographed for later analysis. Results for 10 subjects show that the ocular wavefront aberration near the visual axis is rarely symmetrical about the pupil centre and that, as a result, the phase transfer function is generally non‐zero. Calculated modulation transfer functions at various pupil diameters broadly agree with those of earlier authors but suggest that marked differences occur between individual eyes when the pupil diameter exceeds about 3 mm.
EFFECT OF IMPOSED STEP‐MOVEMENTS AND PULSE‐MOVEMENTS OF THE RETINAL IMAGE ON PERCEPTION OF HUE WITH COLOURED TARGETS
Authors: DITCHBURN R. W. , FOLEY‐FISHER J. A.
Published: December 2007

Abstract— There is strong experimental evidence that colour discrimination depends upon signals originating at colour boundaries. Controlled movements were imposed on a boundary between an illuminated coloured area and a dark area in a previously stabilized image. Red, yellow, green and blue fields were used. Step‐movements of amplitude M min arc and pulse‐movements of amplitude M min arc and pulse width τ s were studied. The movement M50 to produce 50% positive responses for perception of hue was measured as a function of retinal illuminance, boundary length and speed for step‐movements and pulse‐width (τ) for pulse movements. Signal/photon‐noise ratios were calculated.
A SUPRATHRESHOLD MEASURE OF PERCEIVED BRIGHTNESS
Authors: Barbur Vicki A.
Published: December 2007

Abstract— In response to an energy flux density, E(Λ), the output of a linear detector of radiation with spectral response R(Λ) can be calculated by integrating the product R(Λ) *E(Λ) over the spectral range for which R(Λ) and E(Λ) are both non‐zero. This method is also applied when the eye is used as a detector of radiation although the non‐linearity condition and the associated perception of colour as well as brightness make the validity of this approach difficult to assess. The quantity computed in this way when the CIE luminous efficiency function [i.e. the V(Λ) curvel is used as a measure of the spectral response of the eye is referred to as luminance and is often regarded as the objective correlate of perceived brightness. Judd (1951) showed that the use of the CIE luminous efficiency function in this way underestimates the brightness of short wavelength lights. More recently the inappropriate use of the V(Λ) function has resulted in predictions of luminance levels for light‐sources which were not consistent with direct estimates of visual effectiveness (see Kinney, 1983). In this paper, the perceived brightness of coloured lights is investigated using a modified, delayed, brightness‐matching technique. Psychometric response functions were obtained for some twenty coloured test targets which subtended a visual angle of 2° at the observer's eye, whilst adaptation was maintained to a constant white (3900 K) field. The spectral sensitivity functions derived from these data show little variation for a number of different viewing conditions, but they are significantly different from the CIE luminous efficiency function. Brightness discrimination data for a set of selected broad‐band stimuli are related to the prediction of luminance computed by means of both the CIE V(Λ) function and on the basis of the brightness matching function derived from these experiments.
THE ALGEBRA OF SPHERO‐CYLINDERS
Authors: Saunders Harold
Published: December 2007

Abstract— Sphero‐cylinders are shown to be representable by formal vectors. An algebra applicable to sphero‐cylinders is stated and mathematically consistent operations are defined. Examples of practical applications of some operations are given.
THE EFFECT OF ILLUMINATION AND FOVEAL FUSION LOCK ON CLINICAL FIXATION DISPARITY MEASUREMENTS WITH THE SHEEDY DISPAROMETER
Authors: Wildsoet C. F. , Cameron K. D.
Published: December 2007

Abstract— The Sheedy Disparometer is a clinical instrument designed to measure fixation disparity and hence determine forced vergence — fixation disparity curves. The target design includes a central 1.5° fusion‐free area. The effect of introducing a central fixation target to the instrument is investigated along with the influence of ambient illumination level on fixation disparity. All curve parameters, i.e. curve type, slope, X‐ and y‐intercepts were found to significantly alter with the introduction of a foveal lock. Illumination changes did not cause significant differences in any parameter.
THE ARDEN GRATINGS IN OPTOMETRIC PRACTICE
Authors: Yap M. , Grey C. , Collinge A. , Hurst M.
Published: December 2007

Abstract— The use of the Arden gratings (AO contrast sensitivity system) in optometric practice is evaluated. A total of 320 patients presenting for eye examination were screened with the gratings. Sixty‐four eyes (10%) gave abnormal grating scores although results from conventional examination techniques revealed no abnormality. Of the 110 abnormal eyes detected by routine examination techniques, 8 presented with normal grating scores, 6 with “borderline suspect” scores and 96 with abnormal scores. Used in isolation, the failure rate of the Arden gratings to detect ocular abnormality in the patient population was 1.3% and the “false positive” referral rate was 10%.
PLANNING A BACTERIOLOGY PROJECT: A TUTORIAL
Authors: TUXFORD A. F.
Published: December 2007

Abstract— This tutorial paper reviews the action that should be taken at the planning stage of a bacteriological research project to ensure that the final results will have maximal value. Particular consideration is given to the problems of environmental sampling, patient involvement and testing for disinfection and chemotherapy.
TRANSFORMATION OF SPHERO‐CYLINDERS. II. MEAN, VARIANCE AND STANDARD DEVIATION
Authors: Saunders H.
Published: December 2007

Abstract— Following on the ranking hierarchies of transformed sphero‐cylinders established in Part I, expressions for mean, variance and standard deviation are defined.
SOME NOTES ON THE CONSTRUCTION OF “ZONAL ASPHERIC” APHAKIC SPECTACLE LENSES
Authors: Fowler C. W.
Published: December 2007

Abstract— Smith and Atchison (1983) give an optical model of a “zonal aspheric” aphakic lens, but note that lenses mass‐produced to this design philosophy do not show similar optical properties to the model. This paper offers an explanation for this discrepancy, supported by lens measurements.
LATERAL SHORT‐TERM PRISM ADAPTATION IN CLINICAL EVALUATION
Authors: Pickwell L. D. , Kurtz B. H.
Published: December 2007

Data were obtained from a normal clinical population regarding heterophoria, associated phoria and short‐term prism adaptation in an attempt to differentiate between those subjects with symptoms and those without. Correlation between heterophoria, associated phoria, prism adaptation and symptoms was low. A short prism‐adaptation test was found to be of little value in diagnosing decompensated heterophoria in the general population. Subjects diagnosed as having decompensated heterophoria did not have an abnormal short‐term prism‐adaptation system. The clinical implications of these findings are discussed in relation to the diagnosis of decompensated heterophoria and the prescribing of prismatic corrections.
AMPLITUDE OF ACCOMMODATION: POPULATION AND METHODOLOGICAL DIFFERENCES
Authors: Kragha I. K. O. K.
Published: December 2007

A literature survey of amplitudes of accommodation in various countries is presented. Results of push‐up and minus‐lens determination of 447 patients in Nigeria are compared with previous results. A smaller decrement in amplitude due to temperature than previously accepted is suggested.
IMAGE TRACKING OBSERVED WITH A PUPIL‐CENTRING DEVICE
Authors: Burton G. J. , Sharp R.
Published: December 2007

A brief report is given of some observations made during an extended investigation into the subjective image quality of telescopes. For part of the work, a device was required that would indicate directly to an observer the accuracy of eye position, both laterally and longitudinally, with respect to an artificial pupil. This device is described. During use it was observed that the point image produced by the device approximately tracked the eye rotation. This unanticipated property is explained and a different optical arrangement is suggested in order to exploit and enhance this tracking property. The reason for drawing attention to the technique is not only that there may be similar situations in which such devices may be used but also that the tracking property may have other applications, perhaps in a teaching or clinical context.
THE RISE AND FALL OF INTRA‐OCULAR PRESSURE: THE INFLUENCE OF PHYSIOLOGICAL FACTORS
Authors: Buckingham Terry , Young Rhona
Published: December 2007

A number of physiological factors can influence the intra‐ocular pressure of patients with normal, healthy eyes leading to the misinterpretation of tonometric findings. The influence and duration of four commonly encountered factors‐drinking water, coffee, alcohol, and exercise‐were investigated employing a non‐contact tonometer. Drinking 1 litre of water increased the IOP for up to 140 min with a mean maximum increase of 4.4 mmHg. A similar change was induced by coffee, the increase lasting up to 95 min and displaying a mean maximum increase of 4.0 mmHg. The intra‐ocular pressure fell with alcohol consumption by a maximum of 3.7 mmHg, regaining pre‐test values in all subjects after 65 min. Vigorous exercise produced an immediate fall in mean intra‐ocular pressure of 4.3 mmHg, initial pressure being restored in all subjects after 65 min. The impact of such factors upon normal physiology are discussed together with the implications for routine tonometry.
THE SPECTACLE MAGNIFICATION OF FOCAL TELESCOPES
Authors: Long William F. , Woo George C.
Published: December 2007

A generalized expression for spectacle magnification is derived and used to determine the magnification of focal telescopes used to correct ametropia and/or to view objects at finite distances. When applied to low‐powered hand‐held telescopes, the expression predicts a clinically negligible difference between spectacle and nominal magnification.
A QUASI‐STATIC STUDY OF ACCOMMODATION IN AMBLYOPIA*
Authors: Ukai Kazuhiko , Ishhii Makiko , Ishikawa Satoshi
Published: December 2007

Abstract— A method named quasi‐static recording of accommodation is introduced. While accommodative stimulus (AS) is slowly changed over a wide range with a constant velocity (0.2 D s‐1), accommodative response (AR) is continuously measured. AS and AR, respectively, are recorded on the abscissa and the ordinate of an x ‐ y recorder to produce a “quasi‐static” response/stimulus curve.

This method was applied to 28 monocular amblyopic and formerly amblyopic subjects, and the findings were compared with those from their sound eyes. The recordings and subsequent analysis show reduced accommodative amplitude and reduced accommodative accuracy in amblyopic eyes, similar to those reported in previous static measurements of accommodation. In about a half of the amblyopic eyes, the recordings reveal that the fluctuations of accommodation are greater as the target becomes closer. Increased microfluctuation associated with a loss of sensitivity to change of contrast is discussed. This phenomenon suggests that increased microfluctuation is directly associated with reduced performance. In three recovered amblyopes, the accommodative functions were considerably reduced, while the other 10 subjects showed improved functions. It is suggested that, in some cases, the abnormal accommodation is the cause of the amblyopia.
TWO SIMPLE CALCULATING SCHEMES FOR USE IN OPHTHALMIC OPTICS‐I. TRACING OBLIQUE RAYS THROUGH SYSTEMS INCLUDING ASTIGMATIC SURFACES
Authors: Bennett A. G.
Published: December 2007

Abstract— A ray tracing scheme using paraxial approximations is described to allow oblique rays to be traced through lenses or optical systems in which some or all of the surfaces may be astigmatic, even at different axes. It is based on consideration of the prismatic effects introduced at each surface. A numerical example reveals some lesser known properties of the circle of least confusion of astigmatic pencils.
CHANGES IN THE ORIENTATION OF THE AXIS OF ASTIGMATISM ASSOCIATED WITH AGE
Authors: Saunders H.
Published: December 2007

Abstract— A new regression equation for the change in the axis of astigmatism with age, as deduced from cross‐sectional studies, is presented. Possible artefacts arising from the methods used to obtain mean prescriptions are discussed; it is shown that these may result in over‐estimation of the occurrence of oblique cylinders in middle‐age and that a previously demonstrated gradual change of orientation of the axis of astigmatism may have no basis in reality. The need for further longitudinal studies is emphasized.
A TEST BED FOR OCULAR DRUGS*
Authors: Wigham Chris , Hodson Stuart
Published: December 2007

Abstract— Corneal endothelium plays a vital role in maintaining corneal transparency. We describe here a new in vitro technique for detecting acute effects of ocular drugs on corneal endothelium from animal species and post‐mortem human tissue. The technique is based upon trans‐endothelial electrical activity and leads as a consequence, to rapid, unambiguous, quantitative assessments of pharmacological effects upon endothelial barrier function and fluid pump activity.
CITY TESTS AND INFORMATION THEORY*
Authors: Chauhan Balwantray C. , Blocks M. T.
Published: December 2007

Abstracts— The responses of 455 male subjects on both editions of the City University Colour Vision Tests (City 1 and City 2) were recorded after the establishment of each subject's criterial status using the Nagel anomaloscope. Based on the Information Theory, each plate was assigned a contributory weighted score to the total test score. Using informational analysis, a cut‐off point in test score separating normals and defectives was also determined for each test. This scoring system is an improvement on the existing (or manufacturer's) system. The analysis has also shown that the second edition (City 2) is a considerable improvement on the first (City 1). Despite this, even the improved City 2, like its origin, the D‐15, is shown to be poorer than most of the commonly used PIC tests.
SPECTRAL SENSITIVITY FOR OBSERVERS WITH PROTANOMALOUS, EXTREME PROTANOMALOUS AND PROTANOPIC COLOUR VISION
Authors: Kinnear Paul R.
Published: December 2007

Abstracts— Contemporary models of colour vision include a channel for luminosity arising from a combination of some or all of the cone outputs. Accordingly any alteration, reduction or loss at the cone level ought to affect the shape of the spectral sensitivity curve, yet there have been few reports of any significant differences being found between the curves of protanomalous and protanopic subjects. A modified minimum flicker technique was used to determine the spectral sensitivity curves of observers with protanomalous, extreme protanomalous and protanopic vision. Significant differences were found among the mean curves of these categories of vision from 550 nm upwards.
OPTIMIZED FORMS OF NEGATIVE POWER HYDROPHILIC CONTACT LENSES HAVING MINIMUM VOLUME
Authors: El‐Nashar Nabil F. , Hassan Amin F.
Published: December 2007

Abstracts— A design is introduced for soft contact lenses of negative power, having a lenticular anterior surface and a conicoidal posterior surface. Mathematical formulae are derived to calculate the lens volume. The design results in a reduction in lens volume, especially for high powers, while potentially allowing a good fit to the individual cornea to be achieved.
EFFECTS OF PROLONGED FORCED VERGENCE UPON THE ADAPTATION SYSTEM
Authors: North Rachel V. , Dharamshi) Begumpara Sethl (Nee , Henson David B.
Published: December 2007

Abstract— In previous studies the ability of the oculomotor system to adapt to prism‐induced heterophoria has been shown. The phoria that occurs immediately after a prism has been placed before one eye gradually reduces and returns to its original baseline value as the subject is allowed binocular experience while wearing the prism. Little work has been carried out to determine when the adaptation is complete. In this study we report on the results of two experiments designed to determine when adaptation is complete. In the first, the rate of decay of adaptation, i.e. loss of slow fusional vergence, is measured after varying periods of forced vergence. In the second experiment the rate of adaptation to an additional disparity is measured: this should be the same as that before the induced effect if adaptation is complete. The results of this study indicate that although adaptation may appear complete by the criterion that the phoria has returned to its baseline value, the adaptation is unlikely to be truly complete for a much longer period of time has passed.
BETA‐ADRENERGIC RECEPTOR ANTAGONISM IN MYOPIA*
Authors: Rosenfield Mark , Gilmartin Bernard
Published: December 2007

Abstract— A previous study has demonstrated that timolol maleate (0.5%), a non‐selective beta‐adrenergic antagonist, produces in emmetropes a significant reduction in accommodative convergence (AC) during the initial four minutes of a near‐vision task. The present study has examined the effect of timolol on AC for three refractive groups (each comprising N= 20): emmetropes, early‐onset myopes (EOMs), i.e. myopia onset prior to 15 years of age and late‐onset myopes (LOMs), i.e. myopia onset after 15 years. A double‐blind protocol was adopted between timolol and a saline control. AC was derived from accommodation stimuli of 3.3, 4.1 and 4.8 D with changes in heterophoria being assessed using a Maddox rod and tangent scale. The relationship between the ocular hypotensive effect of timolol and anterior corneal curvature was also investigated using a Goldmann applanation tonometer and a two‐position keratometer (Haag‐Streit). Timolol produced a significant reduction in AC in emmetropes but did not induce significant changes in AC in LOMs or EOMs. The timolol‐induced reduction in IOP did not result in any changes in anterior corneal curvature.
DARK‐ROOM METHODS OF ENHANCING DETAILS IN DIABETIC FUNDUS PHOTOGRAPHS: A PRELIMINARY STUDY*
Authors: Shakespeare A. R.
Published: December 2007

Abstract— A technique for the photographic pre‐processing of fundus pictures prior to computer image storage and analysis is described. Contrast enhancement of small details proved to be possible using normal photographic equipment. It is suggested that this method of enhancement may be particularly suitable for the analysis of diabetic changes.
ANALYSIS OF EARLY DIABETIC RETINOPATHY BY COMPUTER PROCESSING OF FUNDUS IMAGES—A PRELIMINARY STUDY*
Authors: Gilchrist Jim
Published: December 2007

Abstract— A number of classification schemes have developed for assessment of fundus changes in the early stages of diabetic retinopathy. Generally, these rely on visual inspection of fundus photographs by trained observers who estimate the degree of retinopathy compared with a set of standard photographs. Computer image processing techniques offer increased accuracy for monitoring subtle changes in retinopathy level and the possibility of more precise classification. The application of image enhancement and analysis to some discrete fundus lesions is demonstrated. Fundus photographs from the ETDRS Classification Scheme are digitized and processed to improve detectability of discrete lesions. Selected areas of an image containing haemorrhages or hard exudates are then magnified, and techniques of spatial filtering and thresholding are used to extract the features of interest from their background. The area occupied by the lesions may then be easily quantified. Results indicate that image processing methods show promise for the improved analysis of retinopathic changes.
FOVEAL AND NON‐FOVEAL MEASURES OF SHORT WAVELENGTH SENSITIVE PATHWAYS IN GLAUCOMA AND OCULAR HYPERTENSION*
Authors: Heron Gordon , Adams Anthony J. , Husted Roger
Published: December 2007

Abstract— Blue‐sensitive cone thresholds (the ability to detect blue test lights presented on a bright yellow background) were measured to examine foveal and central vision field sensitivity in groups of 33 glaucoma, 31 ocular hypertension (OHT) and 24 age matched normal subjects. Results showed these thresholds were substantially reduced (in all areas tested) for the glaucoma group (˜ 0.8 log units) and less reduced for the OHT group (˜0.2 log units), when compared to the normal group threshold. Measures of red‐sensitive and green‐sensitive cone thresholds showed no difference for all three groups. Furthermore, 16% of the OHT group showed visual field abnormalities for the blue‐sensitive cone threshold measure. We conclude that efforts to detect early function loss in glaucoma and OHT could be improved using these measures in clinical practice.
CONTRAST SENSITIVITY DECLINE WITH AGEING: A NEURAL OR OPTICAL PHENOMENON?*
Authors: Elliott David B.
Published: December 2007

Abstract—Previous studies of contrast sensitivity changes with age have produced conflicting results. Most recent reports indicate that, with increasing age, contrast sensitivity at medium and high spatial frequencies decreases. Whether this is caused by reduced retinal illumination due to senile pupillary miosis and increased lens absorption, by the greater light scatter of the aged eye or by retinal and neural celt loss and degeneration is also in doubt. We measured the contrast sensitivity functions of 16 young (mean age 21.5 ± 2.7 years) and 16 older (mean age 72 ± 4.3 years) subjects with normal healthy eyes, using a modified Rodenstock retinometer and a monitor‐based computer system. The former method bypasses the effects of the optical media to measure the contrast sensitivity function of the retinal and neural system alone, while the latter measures the contrast sensitivity function of the whole visual system, including media. The results show the older group to have significantly lower contrast sensitivity at medium (4 c deg‐1,p< 0.1) and high (10.6 c deg‐1p< 0.001; 16.5 c deg‐1,p< 0.001) spatial frequencies. They also suggest that this is due primarily to retinal and neural changes with age, with optical factors having a slight effect at the highest spatial frequency only.
VISUAL ACUITY PREDICTION USING THE VISUAL EVOKED RESPONSE*
Authors: Douthwaite W. A. , Jenkins T. C. A.
Published: December 2007

Abstract— A technique is described for predicting visual acuity in adult humans by using the visually evoked response (VER). This involves using a pattern‐reversal checkerboard with a small check size (5.5. min arc) as the stimulus, and measuring the peak‐to‐trough amplitude of the VER wave arising from it. The technique is therefore both rapid and convenient. The pattern‐reversal rate was varied in order to assess the influence of the temporal modulation on the VER waves. The results suggest that a rapid pattern reversal rate produces a VER which displays a reduced association with spatial processing.
THE CLINICAL SIGNIFICANCE OF CHANGE*
Authors: Reeves B. C. , Hill A. R. , Aspinall P. A.
Published: December 2007

Abstract— Clinicians frequently make judgements about the clinical importance of a change in “score” on visual function tests obtained from patients on successive visits. Almost no normative data for assessing the significance of change in performance on routinely used clinical tests exists, and the importance of collecting such data is emphasized. A description of how normative data for the significance of change can be collected is given, using the Farnsworth‐Munsell 100 hue test as an example. Although there are always limitations to estimates of error variance, the importance of determining the precision of clinical tests, for guiding rational decision making, is stressed.
EXCURSION TESTS OF OCULAR MOTILITY
Authors: Boylan Christine , Clement Richard A.
Published: December 2007

Abstract—Three alternative excursion tests of ocular motility have been compared. A computer model of the mechanics of the extraocular muscles has been used to estimate the tensions developed by the muscles in these tests. On the basis of these calculations we recommend the transverse test in which the positions of the eyes are observed as they track a target moving from the right to the left with a fixed elevation and a fixed depression.
THE USE OF COMPUTERIZED CONTRAST SENSITIVITY, ARDEN GRATINGS AND LOW CONTRAST LETTER CHARTS IN THE ASSESSMENT OF AMBLYOPIA
Authors: Brown V. A. , Doran R. M. L. , Woodhouse J. M.
Published: December 2007

Abstract—Contrast sensitivity measured with an electronic display was compared with Arden gratings and low contrast letter charts in normal and amblyopic children and adults. The low contrast letter charts and the Arden gratings used in the conventional manner revealed no additional information over that obtained by conventional Snellen acuity. However, the interocular differences found with each plate of the Arden gratings compared favourably with the computerized CSF. With the addition of an extra plate to test at a higher spatial frequency, the Arden gratings would be a useful technique for monitoring amblyopia therapy.
GENERALIZATION OF THE TSCHERNING THEORY: OPTIMIZATION OF ASPHERIC OPHTHALMIC LENSES
Authors: Texier Francoise Le , Lenne William , MERCIER Jean‐Louis
Published: December 2007

Abstract—The perfect single vision ophthalmic lens should be free from oblique astigmatism, mean oblique error, distortion and chromatism. At the same time, it should be aesthetic and comfortable. By means of third‐order theory, we show that Tscherning ellipses can be considered to correspond merely to the particular case in which the lens surface is spherical in the three‐dimensional space defined by the conic constant e, the power of the first surface D., and the back vertéx power D. Consideration is given to the best way of building a merit function for final optimization with a classical ray tracing optimization program on a computer.
A REVIEW OF THE USES AND ADVERSE EFFECTS OF TOPICAL ADMINISTRATION OF ATROPINE
Authors: North R. V. , Kelly M. E.
Published: December 2007

Abstract Atropine is used widely in the treatment of a variety of ocular conditions. This article reviews the uses of atropine in children and any adverse ocular or systemic side effects that have been reported after topical instillation.
BAD LIGHT STOPS PLAY
Authors: Campbell Fergus W. , Rothwell Susan E. , Perry Michael J.
Published: December 2007

Abstract The visual performance of cricket batsmen is simulated over a wide range of ambient illumination. When illumination falls to the level at which they usually stop batting (the gloom level) a rapid increase in reaction time commences. It is also the level at which office and car sidelights are turned on and the sensation of “gloom” occurs.
A LONGITUDINAL STUDY OF THE AGE DEPENDENCE OF HUMAN OCULAR REFRACTION—III. THE MEDIATION OF CHANGES FROM DIRECT TO INVERSE ASTIGMATISM EXAMINED BY MEANS OF MATRICES OF TRANSITION PROBABILITIES
Authors: Saunders Harold
Published: December 2007

Abstract This study enquires into the manner in which the axis of astigmatism changes in the course of individual refractive histories. Specifically, two related problems are addressed: (1) how is the change from direct to inverse astigmatism mediated, and (2) what is the range of relative proportions of each of four variables (spherical ametropia, direct, inverse and oblique astigmatism) that occur in a sample population so that it can be considered randomly sampled and well distributed? Solutions to both problems are obtained by calculation of the probabilities with which transitions between such variables occur. A moderately sized longitudinal sample is used to demonstrate the new method. One of the conclusions is that the biological strategy for the mutation of the astigmatic axis is multi‐faceted and that there is unlikely to be a single cause which can explain the process by which inverse astigmatism is achieved.
Screening for glaucomatous visual field defects: the relationship between sensitivity, specificity and the number of test locations
Authors: Henson D. B. , Chauhan B. C. , Hobley A.
Published: December 2007

The visual field results from 104 eyes with early glaucomatous loss and 1860 normal eyes have been used to derive the relationship between sensitivity, specificity and the number of test locations in a visual field screening test. A logarithmic relationship was found between sensitivity and the number of test locations and a linear relationship between specificity and the number of test locations. The results indicate that large numbers of test locations are not required to reach high levels of sensitivity and that clinically it might be better to screen all patients with a few stimuli quickly than to examine carefully those patients who meet a precondition such as raised intraocular pressure or abnormal disc appearance.
The effect of vergence adaptation on convergent accommodation
Authors: Rosenfield M. , Gilmartin B.
Published: December 2007

This study investigates whether, during a sustained near‐vision task, the convergent accommodaton (CA) derived initially form the fast (reflex) vergence response is subsequently maintained by tonic (adaptive vergence. CA was examined during the course of a 3 min near‐vision taks (viewing distance 33cm) in 10 emmetropic subject. Vergence was stumulated by the introduction of a 6δ base‐out prism before the right eye while the open‐loop accommodative response of the left eye was measured at approximately 1 s intervals using an objective infra‐red optometer. In a control condition the subject viewed the target through a plano lens (Oδ) The accommodation loop was opened by the subject viewing near‐type through 0.5 mm diameter pinholes. Pre‐ and post‐task measurement of heterophoria was made using a Maddox rod and prism bar. Regression of post‐task heterophoria to the pre‐task value indicated that adaptation to the vergence stimulus had occurred. However, there was no significant reduction in induced CA during the task. As the onset of adaptation does not produce any fall in CA, it is concluded that both reflex and adaptive vergence act as a stimulus to CA. This finding is discussed with regard to models of accommodation‐vergence interaction.
Observation of two structures of the tear film lipid layer
Authors: Forst G.
Published: December 2007

The behaviour of the tear film exposed to the atmosphre for a relatively long time was observed by means of a Nomarski kmicroscope and the Zeiss slit‐lamp microscope SL 75. It was observed that the lipid layer of the tear film on the naked eye as well as over the contact lens consists of two structures: the homogeneous structure and a structure exhibiting a micell‐like one. The phenomenon is explained in terms of the specific properties of the different lipids in the gland secretions.
The effect of a foveal scotoma on the visual lobe
Authors: Foley‐Fisher J. A. , Murphy K. st. J.
Published: December 2007

One‐dimensional visual lobes representing the detectability of a small bright target on an unstructured background were measured at several contrast levels, both with and without an artificial foveal scotoma. The effect of the scotoma on the lobe is shown to be restricted to the area of the retina covered by the scotoma, and detection ability is unaffected outside this area.
Schematic eyes for domestic animals*
Authors: Coile D. C. , O'Keefe L. P.
Published: December 2007

Schematic and reduced eyes for the horse, cow, sheep, pig, cat, and dog were calculated from optical parameter values obtained from the literature. Calculations were performed with the aid of a computer program using standard Gaussian equations and a homogeneous lens model. Calculated schematic eyes had refractive states within 1.5D of emmetropia; retinal image sizes ranged from 0.22 (cat and dog) to 0.44 (horse) mm/deg. The cat eye presented here is more nearly emmetropic than a previously published cat schematic eye. The effects of altering refractive indices, radii of curvature, and thickness of refractive components upon refractive state and retinal image size are examined. The largest differences resulted from changes made to refractive indices of the lens and vitreous and to the vitreous depth
Light transmission through the human eyelid: in vivo measurement
Authors: Moseley M. J. , Bayliss S. C. , Fielder A. R.
Published: December 2007

We describe an in vivo measurement technique for determining the transmission of light through the human eyelid and present data from three human subjects. The relevance of the transmission measurements are discussed in relation to (1) clinical electrophysiology and (2) the effects of light on the developing visual system.
Fluctuations in intra‐ocular pressure with sleep:I. Time course of IOP increase after the onset of sleep
Authors: Brown Brian , Morris Phillip , Muller Craig , Brady Andrew , Swann Peter G.
Published: December 2007

Ten normal subjects slept over a series of four nights for time periods of 30 minutes, 1, 2 and 4 hours. Intra‐ocular pressure (IOP) measurements were made using a non‐contact tonometer before and after sleep. The subjects showed a significant increase in IOP of 3.45 mm Hg after 30 minutes of sleep and a further IOP increase thereafter to 6.41 mm Hg above baseline. Such increases in IOP after sleep in normal subjects suggest that glaucoma patients and those suspected of having glaucoma should be monitored overnight to assess their IOP control mechanisms.
Correlations between ocular optical components, height and head circumference
Authors: Rasooly R. , Zauberman H.
Published: December 2007

Correlations between the ocular optical components, height and head circumference were investigated in 144 subjects. Refraction had a higher correlation with axial length than with corneal curvature. On the other hand, height and head circumference had a higher correlation with corneal curvature than with axial length. These results express the dependence of refraction on the axial length and suggest a similarity between corneal and skeletal growth, compared with the relatively independent elogation of the eye. Refraction correlated significantly with head circumferences but not with height, relations which may be explained by considering some of the optical components that determine refraction, rather than treating refraction as a single factor.
Disparity‐induced accommodation in late‐onset myopia
Authors: Rosenfield M. , Gilmartin B.
Published: December 2007

The effect of disparity‐vergence on the accommodation response (AR) was measured in 10 late‐onset myopes (LOMs) and 10 emmetropic subjects during the course of a 10 minute near‐vision task (working distance 33cm). Disparity was induced by the introduction of 3 and 6Δ base‐out prisms placed before the right eye, and the resulting AR for the left eye was measured at 1 min intervals using an objective infr‐red optometer. LOMs showed a significant increase in AR with increasing disparity whereas emmetropes showed no significant differnce in AR for all disparity conditions. The implications of these findings are discussed with reference to the aetiology of late‐onset myopia.
Accommodation and convergence: effects of lenses and prisms in ‘closed‐loop’ conditions
Authors: Ramsdale C. , Charman W. N.
Published: December 2007

Experiments are described in which the steady‐state accommodation response to binocularly viewed targets at various distances in the range 0.2–5 m was measured by laser optometry in normal, near‐emmetropic subjects. Responses were determined with naked‐eye viewing and when equal pairs of either spherical lenses or base‐in or base‐out prisms were placed before the eyes. Snellen acuity was also measured under the same range of conditions. The results show that, although the most accurate accommodation responses were found under natural viewing, the response accuracy was remarkably robust against both lenses and prisms. There was, however, always some change in response level to any increment in lens or prism power. The results are discussed in terms of earlier theories and data on the general relationship between accommodation and convergence.
Accommodative performance for chromatic displays
Authors: Lovasik John V. , Kergoat Hélène
Published: December 2007

Over the past few years. video display units (VDUs0 have been incorporated into many varieties of workplaces and ocupational demands. The success of electro‐optical displays in facilitating and improving job performance has spawned interest in extracting further advantage from VDUs by incorporating colour coding into such communication systems. However. concerns have been raised about the effect of chromatic stimuli on the visual comfort and task eficiency‐because of the chromatic aberration inherent in the opties of the human eys. In this study. We used a computer aided laser speckle optometer system to measure the accommodative responses to brightness‐matched chromatic letters displayed on a high‐resolution RGB monitor. Twenty‐responses to brightness‐matched chromatic letters displayed on a high‐resolution RGB monitor. Twenty‐visually normal. paid volunteers in a 22 35 year age category served as subjects. Stimuli were 14–21‐28 minutes of are letters presented in a monochromatic (white.red.green or blue. on a black background) or multichromatic blue red, blue green. red‐green, foreground background combinations) mode at 40 and 80 cm viewing distances. The results demonstrated that while the accommodative responses were strongly nfluenced by the foreground ‐back ground colour combination the group‐averaged dioptric difference across colours was relatively small. Further. accommodative responses were not guided in any systematic fashion by the size of latters presented for fixation. Imlications of these findings for display designs are discussed.