bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prenatal diagnosis of unilateral tibial hemimelia
Authors: Dreyfus M. , Baldauf J.‐J. , Rigaut E. , Clavert J.‐M. , Gasser B. , Ritter J. 
Published: July 2002

AbstractWe describe a case of unilateral tibial agenesis which was initially observed at 21 weeks' gestation. Unlike bilateral tibial hemimelia syndrome, a rare autosomal dominant condition, unilateral tibial agenesis, which accounts for about three‐quarters of all newborns with this condition, has not previously been described. This case could have been a sporadic abnormality but, in view of the association with other observations (distal bifurcation of the femur, club foot), could be considered as an autosomal recessive inherited condition with variable penetrance. Ultrasonographic features and the genetic prognosis are discussed. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Intracardiac fibrin adhesive for selective fetocide in twin pregnancy: report of three cases
Authors: Dumler E. A. , Kolben M. , Schneider K. T. M. 
Published: July 2002

AbstractIntracardiac fibrin adhesive was used for selective fetocide in three diamniotic twin pregnancies at 18–24 weeks' gestation (trisomy 21: n = 1; ultrasound evidence of major malformation: n = 2). Two of the three pregnancies were complicated by an intra‐amniotic infection leading to pregnancy loss but one patient (with a monochorionic twin gestation) delivered a normal baby prematurely in the 31st week of pregnancy. The technique, complications and pregnancy outcomes are discussed. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Luminance and chromatic contrast effects on reading and object recognition in low vision: a review of the literature
Authors: Eperjesi Frank , Fowler Colin W. , Kempster A. Jayne 
Published: July 2002

SummaryThis paper reviews the literature on the effects of luminance and chromatic contrast on reading and object recognition in low vision. The general consensus is that whereas luminance contrast can enhance reading and object recognition for some low vision subjects, chromatic contrast does not aid low vision reading but may be useful in low vision object recognition. Although providing useful theoretical results, the experimental designs have so far been remote from the conditions that low vision patients may experience in the home and work environment. Suggestions are made for an ‘ideal’ experimental design and details of current research, using conditions more likely to be experienced by low vision subjects in everyday life, are given. This research makes use of a recently developed instrument, the Intuitive Colorimeter®.
The effect of field of view size on steady‐state pupil diameter
Authors: Stanley Philip A. , Davies A. Kelvin 
Published: July 2002

SummaryStudies of the relationship between luminance and pupil diameter have produced widely differing results. This research note explores the possibility that this is due, in part, to differences in the size of the adapting fields used by various workers. We present measurements of pupil diameter as a function of luminance for a variety of field subtenses. The results indicate a consistent trend for smaller subtenses to produce less pupil constriction. For field diameters of up to 25°, replotting the data in terms of corneal flux density (i.e. the product of luminance and subtended area) causes an approximate convergence onto a single function described by D = 7.75 − 5.75 [(F/846)0.41/((F/8460.41 + 2)] where D is the pupil diameter (mm) and F is the corneal flux density (cd m−2 deg2). This equation should be of some practical use in estimation of natural pupil diameter.
A new computerised video‐aberroscope for the determination of the aberration of the human eye
Authors: Walsh Glyn , Cox Michael J. 
Published: July 2002

SummaryWe have developed a video‐based system for the acquisition and analysis of images produced by an aberroscope. The aberroscope uses a helium–neon laser to project a shadow image of a grid onto the retina. The retinal image is, in its turn, imaged onto a CCD video camera. As the grid forms a shadow image, the position of each grid intersection at the retina is affected by the aberrations of the eye. The emergent beam is imaged by the whole pupil, hence the grid shape is little affected by the eye's optics. We compute the aberrations of the eye by measuring the distortions of the grid. A video‐digitiser converts the video camera image into data that can be processed by an Apple Power Macintosh computer using an image processing program (NIH Image V1.57). The program locates the grid intersection positions and computes the coefficients of a Taylor polynomial that describes the wavefront aberration. This technique has significant advantages over photographic methods that use manual image assessment. It gives immediate image storage and analysis, the ability to screen out poor quality images, requires significantly less or no operator interaction and is less labour intensive.
Detecting progressive visual field loss
Authors: Henson David B. , Darling Mark N. 
Published: July 2002

SummaryInvolvement in shared care projects requires the optometrist to make a series of decisions one of which is an assessment of the visual field data to see if there has been any progression. To aid the optometrist in making this decision, the relationship between inter‐test variability in the visual field and extent of loss has been established for the Henson CFS2000 perimeter. In this study, visual field data were collected, with a supra‐threshold strategy, from 174 eyes (89 patients) over a period of 2 years, there being a total of 595 visual field records. The sample included patients with both normal and glaucomatous visual fields. The results show that analysis based upon the number of stimuli missed at 5 or more dB above the threshold estimate reveals an increasing variability with extent of loss. These data can be used by optometrists to establish the significance of any change in the number of missed stimuli from one visit to the next.
Effect of age on the interaction between the AC/A and CA/C ratios
Authors: Rosenfield Mark , Ciuffreda Kenneth J. , Chen Hai‐Wen 
Published: July 2002

SummaryA number of previous studies have examined the effects of age and the development of presbyopia on either the accommodative convergence to accommodation (AC/A) or convergent accommodation to convergence (CA/C) ratios. However, changes in the interaction of these oculomotor crosslinks with increasing age have received relatively little attention, especially over a wide age distribution. Accordingly, the present study examined both crosslink ratios in 42 subjects ranging from 22 to 65 years of age. A dual haploscope‐optometer was used to measure accommodation and vergence. The response AC/A ratio showed a small but significant positive correlation with age in those subjects under 45 years of age, while no significant correlation was observed between the stimulus AC/A ratio and age for all subjects. The CA/C ratio exhibited a significant negative correlation with age for all subjects. Furthermore, a trend was observed for lower CA/C findings to be associated with higher response AC/A ratios. However, the two ratios were inversely but not reciprocally related, with the mean difference between the CA/C ratio and the reciprocal of the response AC/A ratio being significantly different from zero. These age‐related changes in the output of the oculomotor crosslinks provide further evidence of the continual oculomotor adaptation that occurs concurrent with the loss of accommodative responsivity.
Tear lipid layer structure and stability following expression of the meibomian glands
Authors: Craig J. P. , Blades K. , Patel S. 
Published: July 2002

SummaryIn a masked investigation, tear lipid layer structure and non‐invasive break‐up time (NIBUT) of both eyes of 40 normal subjects were assessed with the Keeler Tearscope® after unilateral manual expression of meibomian fluid from the lower lid. The HIRCAL grid (modified keratometer mire) provided the additional measure of tear thinning time (TTT). Twenty untreated normal subjects formed the control group. No difference in lipid layer structure or stability was observed between the right and left eyes of the controls. The NIBUT of the treated eyes was significantly higher than that of the untreated contralateral eyes which was, in turn, greater than that of the control eyes. Lipid layer thickness in the treated eyes was significantly higher than that in the untreated contralateral eyes and the controls but did not differ between the latter two groups. The TTT of the treated eyes was not significantly different from that of the untreated contralateral eyes but both were significantly higher than that of the controls. Unilateral meibomian gland expression results in increased lipid layer thickness and tear stability. A possible reason for the slight increase in tear stability in the untreated contralateral eyes is a complimentary reflex lacrimation induced by mechanical stimulation of the treated eye. Differences between the results of the Tearscope® and HIRCAL grid are attributed to differences in the techniques of tear stability measurement.
Professional misconduct
Authors: Webster Simon H. 
Published: July 2002

SummaryThe Opticians Act 1989 is the main regulating Act of Parliament for UK optometrists and dispensing opticians. The Opticians Act permits only those who are registered with the General Optical Council to practise. Provision is also made to discipline opticians who fail to meet the required professional standards of the profession. This article looks at the meaning of professional misconduct and the disciplinary procedure.
The magnocellular deficit hypothesis in dyslexia: a review of reported evidence
Authors: Greatrex J. C. , Drasdo N. 
Published: July 2002

SummaryMany reports suggest that the majority of dyslexic children have a measurable disorder of the fast processing pathway of the visual system. This pathway is believed to extend from the retina to the occipital and parietal areas of the brain and is referred to as the magnocellular (M) or transient pathway. Evidence in support of the magnocellular deficit theory comes from several sources, but is not totally consistent. Histological studies have revealed shrinkage and disorganisation of M cells in the lateral geniculate nucleus of dyslexic subjects. Psychophysical investigations of visual persistence, contrast sensitivity to moving sine wave gratings and flicker sensitivity, report atypical results in dyslexic children, reflecting an apparent deficiency in the transient system, although not all psychophysical studies have demonstrated such a deficiency. Visual evoked potential responses to a wide range of stimuli have been reported to be deficient in dyslexic subjects, but again there are dissenting papers. These reports have been subject to critical review and analysis, new techniques specifically to stimulate the magnocellular pathway are described, and the relevance of this research to tinted lens therapies and clinical reading problems is discussed.
Intraocular motility, electrophysiological tests and visual fields in drug addicts
Authors: Pérez J. González , Mato M. Parafita , García A. Segade , Rey A. Díaz 
Published: July 2002

SummaryThe effects of drugs on intraocular motility, retina function and central pathways in a drug addicts population have been studied. The study group were made up of 15 drug addicts. Fifteen healthy subjects who had never used drugs acted as a control group. Refractive state, accommodation, tonometry, assessment of pupillary reflexes, campimetry, visual evoked cortical potential (VECP) and ERG were performed in all cases. All the subjects studied used heroine, 12 used cannabis and 12 used cocaine. Refraction was normal in all cases. Accommodation amplitude in normal subjects ranged from 8.5 to 11.5 D, and from 3.5 to 9.5 D in the drug addicts group. Tonometry indicated a tendency to lower intraocular pressure values. Direct and consensual pupillary reflexes were normal in eight subjects, but were sluggish in the rest. Campimetry showed relative and absolute scotoma in five subjects. VECP were found to be normal in two of the cases, moderately pathological in six and pathological in the remaining seven cases. As for the ERG, it showed non‐specific altered traces in 11 cases. Accommodation amplitude was lower than normal in 20 eyes. The decrease of VECP with altered traces but with an increase of latency, seem to indicate the presence of an alteration in the optical pathway or in the cortical centres. The findings in ERG point out a decrease of amplitudes and an increase of latency in more than half the population studied.
Clinical assessment of ocular response to a multipurpose contact lens care solution
Authors: Bergmanson Jan P. G. , Barbeito Raphael 
Published: July 2002

SummaryThe issue of possible adverse effects of contact lens care solutions on ocular health has been raised in the literature. Possible effects of a multipurpose contact lens care solution (Bausch & Lomb ReNu®) on eight measures of ocular function were evaluated relative to the effects of physiological saline (Bausch & Lomb Sensitive Eyes®). In a randomized, two‐treatment, crossover design, all subjects were treated with each of the two solutions on successive weeks. In 73 subjects, comprised of contact lens and non‐lens wearers, tear break‐up time was measured using the keratometer mire and fluorescein techniques. Measures of autonomic function were vertical palpebral aperture size, amplitude of accommodation, intraocular pressure, pupil size, conjunctival injection, and pupil reactivity. The results indicated that this multipurpose solution provoked no adverse ocular response as determined by the tear break‐up time and autonomic functions, and the multipurpose solution was clinically equivalent to physiological saline. These results apply to both contact lens wearers and non‐lens wearers. Additional findings speak of the unreliability of the fluorescein method for measuring tear break‐up time.
The misting characteristics of spectacle lenses
Authors: Margrain Tom H. , Owen Chris 
Published: July 2002

SummaryWhen a spectacle wearer enters a warm environment after having been in a cooler one, his/her spectacles may ‘mist up’ due to the formation of condensation on the lens surface. Both the physical properties of the spectacle lens and a number of environmental factors determine how long spectacles take to demist. The relative misting performance of crown glass, CR39 and polycarbonate spectacle lenses were assessed using a novel technique. A box in which the environmental conditions could be controlled was used first to cool the lens and then to warm it. This change in temperature caused condensation to form on the lens surface. By projecting the image of a grating through the lens onto a linear array of photodiodes it was possible to measure the contrast transmission of the spectacle lens as it demister. Each lens type misted and demisted in a characteristic way. The polycarbonate lens demisted more rapidly than the CR39 lens which, in turn, demisted more rapidly than the glass lens. This indicates that polycarbonate spectacle lenses should be used in conditions where the adverse effects of spectacle misting need to be minimised.
Accommodative response in children and young adults using dynamic retinoscopy
Authors: Leat Susan J. , Gargon Jennifer L. 
Published: July 2002

SummaryAccommodation in children and non‐verbal adults can be difficult to assess using standard subjective techniques and hence is often not evaluated. By using a modification of Nott dynamic retinoscopy, rapid objective evaluation of accommodative function is possible. In this study, accommodative response to a range of accommodative demands was measured in 55 normally sighted children and young adults using dynamic retinoscopy. The data were found to fall into four age groupings: 3–10‐year‐olds' mean accommodation was accurate to within 0.5 D, although 3–5‐year‐olds over‐accommodated slightly, while 6–10‐year‐olds under‐accommodated. Subjects over 10 years of age showed under‐accommodation which increased with accommodative demand. These norms are presented for clinical use against which measurements on an individual paediatric or non‐verbal patient can be compared. Future studies will determine whether specific patient populations, e.g. patients with cerebral palsy or low vision, demonstrate normal or reduced accommodation.
Accommodation responses to flickering stimuli
Authors: Chauhan K. , Charman W. N. 
Published: July 2002

SummaryIt has been suggested that accommodation to visual display unit (VDU) symbols or to stimuli lit by fluorescent tubes or similar temporally modulated light sources may be less accurate due to flicker. Furthermore, if the microfluctuations of accommodation play a part in the control of steady‐state accommodation, the effects of stimulus flicker might affect the quality of this control. Experiments are described in which monocular accommodation stimulus‐response curves for sinusoidal grating stimuli (1.0, 5.3 and 8.9 c/deg) were measured under the following conditions of temporal modulation: (1) square‐wave on‐off modulation to give spatial modulation varying between 0 and 37%; (2) sinusoidal modulation to give spatial modulation varying between 0 and 37%; (3) sinusoidal modulation to give spatial modulation varying between 16 and 32%; and (4) on‐off modulation with varying mark/space ratio. Temporal modulation frequencies were between 0.5 and 7.8 Hz and above the critical fusion frequency (CFF) i.e. 40 Hz. In general, the results suggest that while lower‐frequency flicker may adversely affect the accuracy and stability of the accommodation response, the latter are very little affected by flicker at frequencies ≥ 40 Hz. Thus flicker from fluorescent lamps or VDUs is unlikely to cause systematic accommodation difficulties. The possible relevance of the results to theories which ascribe a role for the higher‐frequency (> 0.5 Hz) accommodative microfluctuations in the control of the response is considered.
A comparison of tests to determine acuity deficits in children with amblyopia
Authors: Geer Indira , Westall Carol A. 
Published: July 2002

SummaryThe usefulness of the Cardiff Acuity Test in the detection of amblyopia was evaluated. Visual function was measured using pattern visual evoked potentials (VEPs), the Cardiff test, and the Bailey‐Lovie Chart in 21 visually normal children and 12 children with amblyopia. The Cardiff test gave higher scores than the Bailey‐Lovie test. The Cardiff test identified five of the 12 children who were classified as amblyopic by the Bailey‐Lovie test. Interocular VEP latency differences identified eight of the 12 children with amblyopia; interocular VEP amplitudes correctly identified nine. We suggest that the challenging Bailey‐Lovie test be used for older children who know their letters well. If the Bailey‐Lovie test cannot be used, VEPs give the most accurate assessment of interocular differences. The Cardiff test holds a bored child's attention and allows the examiner to obtain a useful measure of visual acuity, but it cannot detect mild amounts of amblyopia.
Interocular differences in visual function in normal subjects
Authors: Wood Joanne M. , Bullimore Mark A. 
Published: July 2002

SummaryA commonly used clinical technique for determining whether visual function is abnormal, particularly when a patient is suspected of having unilateral or asymmetric disease, is to compare the visual function of the ‘suspect’ eye to that of the normal eye. This assumes that in normal patients visual function in each eye is equal and that this symmetry is maintained with age. To determine the extent of normal symmetry for clinical measures of visual function, we assessed high and low contrast visual acuity, letter contrast sensitivity and motion sensitivity (Dmin) in both eyes of a group of 91 subjects spanning an age range of 21 to 82 years. For the whole group the interocular differences in sensitivity for each of the tests approximated a Gaussian distribution. The results demonstrate that interocular differences should exceed more than 0.16 and 0.17 logMAR ( 2 lines) for high and low contrast visual acuity respectively, before patients can be considered to be outside the range of normality. For the Pelli‐Robson Chart, interocular differences must exceed 0.23 log CS (1.5 triplets, 4.5 letters) and for Dmin, more than 0.35 log minarc for the differences to be considered abnormal. For low contrast letter visual acuity, there was a trend for the absolute interocular differences to increase significantly with age, but asymmetry remained relatively constant for the other visual measures.
The Heidelberg retina tomograph in glaucoma
Authors: Hosking S. I. 
Published: July 2002

Purpose: To establish the ability of the Heidelberg retina tomograph (HRT) to detect morphological change of the optic nerve head in glaucomatous optic neuropathy and to evaluate glaucomatous nerve fibre layer defects.Introduction: The HRT is a confocal laser scanning microscope designed for three‐dimensional imaging and measurement of the in vivo fundus. The light source is a diode laser operating at a wavelength of 670 mm. Thirty‐two single, two‐dimensional sectional images are recorded within 0.032 s with a repetition rate of 20 Hz, digitised in a frame of 25 × 256 pixels. Sequential viewing of the plates permits three‐dimensional resolution of the image. Use of the HRT enables comparison of change in optic nerve head morphology with change in visual function.Methods: The sample consists of 30 early primary open angle glaucoma subjects showing repeatable glaucomatous field defects on Humphrey 30‐2 analysis and 65 glaucoma suspects with normal Humphrey 30‐2 fields but with multiple risk factors for the development of glaucoma. All subjects are evaluated using white‐on‐white and blue‐on‐yellow visual fields as well as HRT analysis of the optic nerve head and retina at three‐month intervals over a 15‐month period.Discussion: We have demonstrated the need for consistent image scaling in prospective follow‐up (Hosking et al., 1995), a facility to be incorporated in the next software revision; the importance of selecting an optimum scan; and that the correction of astigmatism required for quality image acquisition results in image distortion. The application of nerve head analysis software to demonstrate localised wedge‐shaped nerve fibre bundle defects is illustrated and further modification of the software to demonstrate more subtle subclinical nerve fibre layer defects will be discussed.