bluuebunny/crossref_metadata_2025 huggingface dataset:
Stages in coming to terms with reflection: student advanced nurse practitioners' perceptions of their reflective journeys
Authors: Glaze Jane E.
Published: July 2002

Stages in coming to terms with reflection: student advanced nurse practitioners' perceptions of their reflective journeys

Aim of the study. To explore student Advanced Nurse Practitioners' (ANPs) experiences of reflection.

Background. The development of student ANPs' reflective abilities as part of the implementation of a Master's Course in Advanced Nursing Practice at Wolverhampton University provided the background to the study. Developing reflective abilities was seen as an essential component of ANP development. To facilitate this process a preentry degree level reflective practice module and a reflective component for the level 4 (Master's level) practice module were devised.

Rationale. This was a new educational initiative and this study provided the opportunity to explore students' experiences of it following completion of the reflective modules.

Design/methods. A qualitative methodology was used. Fourteen ANP students were interviewed and their reflective learning contracts were analysed. Colaizzi's (1978) seven‐stage model guided data analysis.

Findings. The findings were categorized under the headings of: (i) reflection as a transforming process, (ii) reflective journeys, (iii) worldviews. This paper presents an analysis of the second category reflective journeys. It identifies a number of stages in the development of students' reflective abilities.

Conclusions. The conclusions have implications for those involved in reflective curriculum development, and for those seeking to develop reflective abilities in students.
Soil seed banks and the effects of meadow management on vegetation change in a 10‐year meadow field trial
Authors: Smith R.S. , Shiel R.S. , Millward D. , Corkhill P. , Sanderson R.A.
Published: July 2002

Enhancement of plant species diversity is often an objective in grassland management for wildlife conservation. Such management regimes may also change the species composition of soil seed banks, which may themselves affect future vegetation change. We compared soil seed banks and vegetation from a long‐term meadow management trial and from a series of traditionally managed species‐rich meadows in northern England, UK.

The management trial used three hay‐cut date treatments (14 June, 21 July and 1 September), two fertilizer treatments [no fertilizer or 25 kg nitrogen ha−1 plus 12·5 kg ha−1 phosphate (P2O5) and potash (K2O)] and two seed‐addition treatments (no seed, seed of many species sown 1990–92). Soil seed banks were assessed in 1998. Subsequent vegetation development under these treatments, and under an additional farmyard manure treatment, was assessed in 2000.

Most seed was in the 0–5‐cm soil layer and most of the frequent species germinated in the autumn. Short‐ and long‐term persistent seed banks were most abundant. The species composition of the seed banks and the vegetation in the trial, and in the traditionally managed meadows used as a control, were distinctly different, the meadow trial seed bank being the most uniform.

An ordination of simulated plant communities based on the UK National Vegetation Classification provided a wider framework for comparing vegetation and seed banks with the species composition of British meadow communities, some of which are also found in Europe. The soil seed banks throughout the meadow trial plots and the control fields were very similar in species composition to that of the vegetation in agriculturally improved meadows. However, there were many more species in the soil seed bank of the traditionally managed control meadows.

In 2000, only the seed‐addition treatment increased the species richness of the vegetation. Farmyard manure and mineral fertilizer had similar effects, increasing the cover of Poa trivialis and Rumex acetosa and decreasing the cover of Rhinanthus minor and Anthoxanthum odoratum.

It was concluded that the development of the soil seed bank probably lags behind increases in vegetation diversity initiated by seed sowing. This emphasizes the need to introduce additional species as seed when increased diversity is a target for the restoration management of previously intensively managed grasslands.
African and African Caribbean users’ perceptions of inpatient services
Authors: Secker J. , Harding C.
Published: July 2002

It has been suggested that well‐documented differences in African and African Caribbean people’s contact with mental health services may stem from the organization, processes and practices of services themselves. This article presents the findings of a qualitative study which explored the inpatient experiences of a sample of African and African Caribbean people. Although some positive experiences were described, in the main, participants’ accounts revolved around a sense of loss of control and around experiences of overt and implicit racism. Underpinning these experiences were relationships with staff that were perceived to be unhelpful. On the basis of both the positive and negative experiences described, we draw conclusions about the changes required to ensure that inpatient services more effectively meet the needs of this group.
Conservation of the Juan Fernandez firecrown and its island habitat
Authors: Roy Michael S. , Torres-Mura Juan Carlos , Hertel Fritz , Lemus Marina , Sponer Renate
Published: July 2002

The Juan Fernandez Islands constitute two distantly separated (182 km) major islands, of which Isla Robinson Crusoe is the closest (667 km) to the Chilean mainland, and a number of smaller surrounding islets. The endemic Juan Fernandez firecrownSephanoides fernandensisonce inhabited both major islands and numbered many thousands. Today it exists only on Isla Robinson Crusoe and numbers just a few hundred. Another hummingbird, the green-backed firecrownS. sephaniodes, inhabits this island but also occurs on the mainland. The islands are in ecological meltdown as a result of the removal of much of the native (largely endemic) biota. This degradation has been exacerbated by introduced herbivorous and carnivorous mammals, which are extirpating all that remains. In a previous investigation the authors assessed the evolutionary relationships and genetic variation in the Juan Fernandez firecrown population. They showed that the species: (i) is a relative of the high Andean hummingbirds; (ii) is a close sister species of the green-backed firecrown; (iii) dispersed to the islands approximately 0.5–1 million years ago, unlike the green-backed firecrown, which is probably a very recent invader; (iv) maintains some genetic variation, although significantly lower than that found in the green-backed firecrown island population. Because of their relatively recent divergence the authors aimed to find out if the two species compete for resources. In addition, they assessed the conservation options for the Juan Fernandez firecrown and provided recommendations for its management. They concluded that the survival of the Juan Fernandez firecrown is inextricably linked to the holistic restoration of ecosystem/ community function of the island. The initial step must involve the removal of introduced mammals, followed by replanting of native flora. Although the authors do not support the use of captive propagation as a general conservation tool, they believe that, because the Juan Fernandez firecrown is composed of only one small population that is under extreme threat of extinction, a captive population should be established.
Performance of a new pubertal self‐assessment questionnaire: a preliminary study
Authors: Taylor  , Whincup  , Hindmarsh  , Lampe  , Odoki  , Cook
Published: July 2002

We describe the performance of a new, self‐assessment questionnaire that aims to measure pubertal status by using gender‐specific line drawings of the Tanner puberty stages. The study was carried out on 103 children aged 12–16 years attending a paediatric endocrinology outpatient clinic and used physical examination by clinic doctors as the ‘gold standard’. Of 133 consecutive, eligible children, 108 (81%) agreed to participate in the study. Data were collected from 62 (60%) males and 41 (40%) females. Mean age was 14.78 years (SD = 1.26 years, range 12.08–16.98 years). For the pubic hair distribution Tanner stage, there was agreement to within one Tanner stage for 90 children (88%), weighted kappa statistic for inter‐rater agreement = 0.68 [95% CI 0.49,0.87]. For the female breast/male genitalia Tanner stage, there was agreement to within one Tanner stage for 75 children (76%), kappa = 0.48 [95% CI 0.31,0.64]. The children tended to underestimate their stage of pubertal development. Overall, the kappa statistics implied good agreement for the pubic hair question and moderate agreement for the breast/genitalia stage question in both girls and boys. The questionnaire may prove useful in situations such as large‐scale epidemiological studies, in which direct examination of children to determine pubertal status is not possible, and further validation in normal adolescents is warranted.
A comparison of recent trends in infant mortality among twins and singletons
Authors: Parker  , Schoendorf  , Kiely
Published: July 2002

Overall infant mortality rates have steadily declined in recent years. The goal of this study was to examine whether recent declines in infant mortality were similar for twins and singletons, and to assess the impact of differing birthweight distributions on these relationships. Linked birth and infant death records for 1985–86 and 1995–96 were used to calculate infant mortality rates for twins and singletons for the two time periods. Bootstrap simulations were used to estimate rates of decrease between the two time periods and to determine whether these rates differed between twins and singletons. Between 1985–86 and 1995–96, infant mortality among twins declined significantly faster than among singletons (36% vs. 29%, P < 0.05). This difference was true for both black and white infants (black: 28% for twins vs. 22% for singletons; white: 38% for twins vs. 31% for singletons). Within birthweight categories, infant mortality declined more rapidly among twins than among singletons, although differences were not always significant. Factors and circumstances that contributed to the infant mortality decline in the United States have benefited twins to a greater extent than singletons.
Development and survivorship of Carpophilus hemipterus (L.), Carpophilus mutilatus Erichson and Carpophilus humeralis (F.) (Coleoptera: Nitidulidae) over a range of constant temperatures
Authors: James David G , Vogele Beverley
Published: July 2002

Eggs of Carpophilus humeralis (F.) and Carpophilus mutilatus Erichson developed at constant temperatures from 20–37.5°C, while Carpophilus hemipterus (L.) completed development at temperatures from 20–42.5°C. Carpophilus hemipterus completed larval and pupal development at all temperatures up to and including 40°C. Carpophilus mutilatus reached adulthood at 37.5°C, but C. humeralis was only able to complete egg to adult development at temperatures up to 32.5°C. Rates of development changed in a linear fashion with temperature. The development of C. hemipterus eggs and larvae was faster at all temperatures than the other two species (P < 0.05). Developmental duration from egg to adult for the three species ranged from 47–65 days at 20°C to 14–18 days at 32.5°C. The fastest development was recorded for C. hemipterus at 37.5°C (13.4 days). Lower developmental zeroes (DZ) were similar for the eggs, larvae and pupae of each species, ranging between 14.0–16.0°C. Estimates of DZ for egg–adult development were 15.3°C (mutilatus), 15.4°C (humeralis) and 14.6°C (hemipterus). Egg to adult development required 260.4 (hemipterus), 297.6 (humeralis) or 320.0 (mutilatus) degree‐days. Survivorship was greatest for all species at temperatures between 25–30°C, with the larval stage suffering most mortality from higher or lower temperatures. The use of degree‐day estimates to predict timing of adult generations of Carpophilus spp. is discussed with respect to the management of these pests in stone fruit orchards in southern Australia.
A systematic review of foot ulcer in patients with Type 2 diabetes mellitus. II: treatment
Authors: Mason J. , O’Keeffe C. , Hutchinson A. , McIntosh A. , Young R. , Booth A.
Published: July 2002

Aim To assess the value of treatments for foot ulcers in patients with Type 2 diabetes mellitus.

Methods A systematic review of interventions to treat diabetic foot ulcers.

Results The evidence base for treating infections and dressing wounds is poor. A number of new and potentially promising treatments are being developed but currently available studies are often small, inadequately powered and use different methods and outcomes.

Conclusions Given the prevalence, morbidity and healthcare costs of diabetic foot disease, it is surprising that available trials provide inadequate evidence to improve upon current empirically based treatment approaches. Substantial effort and resources should be deployed in order to investigate both new and existing treatments in a co‐ordinated, systematic and consistent manner, so that a proper evidence base can be established for this important disease area.
Prevalence of gestational diabetes mellitus – do the new WHO criteria make a difference?
Authors: Schmidt M. I. , Matos M. C. , Reichelt A. J. , Forti A. Costa , De Lima L. , Duncan B. B. , Group For The Brazilian Gestational Diabetes Study
Published: July 2002

Aims To describe the prevalence of gestational diabetes mellitus (GDM) according to the 1998 WHO provisional recommendations and compare it to that found with previous 1985 WHO criteria.

Methods A total of 5564 consecutive women aged 20 years or more without diagnosis of diabetes mellitus outside of pregnancy in general prenatal care clinics of the National Health Service in 6 state capitals of Brazil, between their 20th and 28th gestational weeks were enrolled.

Results Of the 5004 women who completed a 75‐g oral glucose tolerance test, 379 (7.6%, 95% confidence interval (CI) 6.9% to 8.4%) had GDM by the 1998 criteria (fasting glucose  7.0 mmol/l or 2 h glucose  7.8 mmol/l). Of these 379 cases, only 21 (5.5%) had hyperglycaemia in the range considered diabetes mellitus outside pregnancy (fasting glucose  7.0 mmol/l or 2 h glucose  11.1 mmol/l); the remaining 358 (94.5%) had hyperglycaemia in the impaired glucose tolerance range (fasting glucose < 7.0 and 2 h glucose  7.8 mmol/l and < 11.1 mmol/l). Using the 1985 criteria (fasting or 2 h glucose  7.8 mmol/l), 378 cases of GDM were found, 15 in the diabetes range and 363 in the impaired glucose tolerance range.

Conclusions Prevalence of GDM is minimally altered by the new WHO definition. Although GDM is a common condition, the vast majority of the cases have hyperglycaemia in the range considered impaired glucose tolerance outside pregnancy.
Video‐photorefraction: the relationship between blur circle diameter and refractive error
Authors: Jennings Deborah S. , Jennings J. A. M.
Published: July 2002

When using a videorefractor (VPR‐1) the margins of the defocused blur circles are sometimes poorly defined and difficult to locate. To investigate the effect this may have on the apparent refractive error, the relationship between blur circle diameter and refractive error was found by videoing circles of known size and inputting these data as pupil and blur circle diameters. The results indicate that for accuracy of 0.50 D blur circles need to be defined to ≃ 1 mm.
The presbyopic add. II. Age‐related trend and a gender difference
Authors: Pointer Jonathan S.
Published: July 2002

New transverse clinical data are presented which confirm and extend earlier results to be found in the literature describing the time course of presbyopia–as indicated by the magnitude of the binocular spectacle add–in normally sighted male and female Caucasian subjects. An initial steep increase in add requirement beginning in the early forties becomes relatively slower but still of significance beyond the mid‐fifties. This observation is correlated with the age‐related progressive decline in the amplitude of accommodation, itself a consequence of physiological changes in the crystalline lens and capsule. The continuing need for an increase, albeit at a reduced rate, in the positive near supplement beyond the mid‐to‐late fifties–by which time little or no useful accommodation is available–is now attributed to the visually disruptive effects within the high spatial frequency domain of progressive age‐related lenticular changes. The magnification afforded by the positive add increases spatial grain and thereby enhances visibility of detail in an ageing visual system free of any gross senile visual pathology. A small but consistent gender difference is revealed in presbyopic corrections: physiological and physical bases are suggested for the observation that females require an add of greater magnitude than their age‐matched male counterparts.
Evaluation of the effects of saline versus bicarbonate‐containing mixed salts solutions on rabbit corneal epithelium in vitro
Authors: Doughty Michael J.
Published: July 2002

Rabbit corneas were incubated, over 4 h in vitro, with the corneal epithelial surface exposed to various solutions to assess their utility as incubation solutions for physiological, pharmaceutical or toxicological studies. The corneal endothelium was perfused with a 35 mm bicarbonate–mixed salts solution equilibrated at 36°C. Corneal thickness, corneal hydration or epithelial cell appearance (as assessed by scanning electron microscopy) were found to be similar to in vivo if a 35 mm bicarbonate, mixed salts solution (equilibrated with 5% CO2–air) was used for the epithelium. Some swelling (14 μmh−1), increased hydration and minor cell exfoliation were seen if this 35 mm bicarbonate solution was equilibrated with 5% CO2–95% O2 (hyperoxia). Solutions with only 5 mm bicarbonate (0.5% CO2–air) produced rapid swelling, large increases in hydration and marked cellular damage. Slightly hypertonic (310 mOsm kg−1) solutions containing 5 mm bicarbonate caused some swelling at 15 μm h−1, small increases in hydration and some cell damage but the swelling and cellular damage were further reduced by making the solution slightly more hypertonic (325 mOsm kg−1) by addition of NaCl and KCl. Saline (NaCl 0.9% or 0.97%) or phosphate‐buffered saline (PBS) (300 mOsm kg−1) produced swelling at 21–28 μm h−1, 30% increases in hydration and almost total destruction of the superficial cell layers. These studies confirm in vivo experiments that saline (and also buffered saline solutions) are rather toxic to the corneal epithelium and thus should not be used as epithelial incubation solutions. Even when using mixed salts solutions and even with bicarbonate present, small differences in composition can have marked effects on corneal thickness, hydration or cell appearance. Hyperoxic solutions appear to be mildly cytotoxic compared with normoxic solutions.
The Waterloo Vision and Mobility Study: postural control strategies in subjects with ARM
Authors: Elliot David B. , Patla Aftab E. , Flanagan John G. , Spaulding Sandi , Rietdyk Shirley , Strong Graham , Brown Steve
Published: July 2002

Binocular visual function and standing balance control was assessed in 16 subjects with age‐related maculopathy (ARM) (mean age 73.9 ± 7.4 years) and 19 controls (mean age 69.1 ± 5.5 years). Balance control was assessed using the center of pressure signal from force plate data. It was quantified using the root mean square (RMS) error of the amplitude, sampled over a 1 min period. This was evaluated during normal standing, and while the input from the kinesthetic and/or visual systems were disrupted. The two subject groups showed significantly different RMS values across conditions (P < 0.005). The differences in RMS between ARM and control groups were only significant when the input to the kinesthetic sensory system was disrupted. Our results suggest that in the normal standing condition, the kinesthetic and vestibular systems compensated for the lack of useful information from the visual system in ARM subjects. When kinesthetic system input was disrupted, balance control of the ARM group was significantly poorer than the control. There was a weak correlation between postural control and contrast sensitivity. Various strategies for preventing falls in elderly patients with low vision are suggested.
Amblyopia: a tale of two approaches
Authors: Hess Robert F.
Published: July 2002

Our understanding of the physiological basis for amblyopia in humans has undergone dramatic changes over the past two decades. The first such change occurred when we were first able to record from single neurones in different parts of the visual pathway and develop neural models of the anomaly. The second came from psychophysical investigations and evaluations of these animal models. Our understanding has progressed from one focused on the properties of single cortical cells to an appreciation of the anomalous behaviour of cellular networks.
Outcome of referrals for suspected glaucoma
Authors: Harper Robert , Reeves Barnaby , Hill Adrian
Published: July 2002

The source, content and accuracy of 178 referrals to Oxford Eye Hospital for suspected glaucoma were examined.

The majority (82.6%) of referrals for suspected glaucoma were initiated by optometrists, other referrals being initiated by general practitioners (10.1%) and ophthalmic medical practitioners (7.3%). Most referrals (86.5%) reported the intraocular pressure (IOP) level. Comments on the optic disc were recorded in 53.9% of referrals. Only 21.3% of referrals mentioned the status of the visual field. The findings of all three ‘standard’ glaucome measures (i.e. IOP and the status of the optic disc and visual field) were reported in only 15.2% of referrals.

A visual field defect consistent with glaucoma was found in 38.2% of referrals and a further 9.6% of referrals were prescribed treatment for glaucoma/ocular hypertension but had no manifest visual field defect. Approximately one‐third of referrals (34.2%) were considered ‘normal’ and were discharged. The remainder of referrals were either followed up as glaucoma suspects (9.6%) or were considered ‘abnormal’ but non‐glaucomatous (8.4%).

There was evidence to suggest that (1) optometric referrals were more accurate than referrals from GPs and OMPs; and (2) referrals combining information from all three standard screening measures were more accurate than those based on IOP alone.

These findings support previous surveys by the International Glaucoma Association. At least one‐third of referrals for suspected glaucoma are false positives. Visual field screening appears to be used very infrequently by primary vision carers suggesting that the false negative rate may also be high.
The source of disparity vergence innervation determines prism adaptation
Authors: McCormack G. , Fisher S. K.
Published: July 2002

A physiological model of prism adaptation argues that adaptation magnitude and rate are functions of the magnitude of reflex vergence innervation. It has also been shown that there is reduced prism adaptation magnitude for a given disparity stimulus where only peripheral sensory fusion is present (the ‘eccentricity effect’). This study attempted to determine whether the eccentricity effect is attributable to reduced reflex vergence innervation in peripheral fusion. Experiments were run in a Maxwellian view haploscope. Convergence and divergence adaptation to 6 Δ disparity stimuli were quantified for seven binocularly normal subjects using subjective heterophoria measurements. Vergence response during central or peripheral fusion was quantified objectively by infrared oculography. Six of seven subjects revealed an eccentricity effect. However, in three of seven subjects the eccentricity effect was not predictable from the manifest vergence response. The results suggest that the source of reflex vergence innervation affects prism adaptation. A model is proposed whereby different sources of reflex disparity vergence innervation stimulate prism adaptation by way of separate neurological pathways of differing responsiveness.
Spatial interference with vertical pistol sight alignment
Authors: Carkeet Andrew , Brown Brian , Chan Peter
Published: July 2002

When competition pistol shooters aim, they perform four basic visual alignment tasks. With optimal stimuli such tasks can be performed with exquisite sensitivity. However, pistol sights and the target may not constitute the optimal stimuli, and this may impose limits on how well shooters perform. By simulating pistol sights and targets on a computer monitor, we investigated how the vernier task of aligning the top edges of the front and rear pistol sights was affected by the proximity of the target aiming mark. Alignment random error in this task, an analogous measure to vernier acuity, was unaffected by the proximity of the aiming mark; however, alignment systematic error did change significantly as the proximity of the aiming mark changed. This effect was unlikely to significantly change pistol shooting performance as shooters can adjust their sights to compensate for systematic errors. Likewise, compared to the vertical spread of shots on the pistol target, alignment random error was extremely small (only 10s arc), which implies that other sources of variation limit pistol shooting performance.
Thickness extrema at the edge of astigmatic lenses including those with straight, circular and elliptical edges
Authors: Harris W. F.
Published: July 2002

The problem of locating the points of maximum and minimum thickness at the edge of a lens, and of calculating the thickness at those points, is examined for lens powers and for edge shapes in general. The edge extremal problem, as the problem is called, is solved explicitly for general powers along straight cut edges. The extremal problem is also analysed for lenses with circular and elliptical edges but explicit solutions are obtained only for centrally cut lenses, that is, lenses with coincident optical and geometrical centres. For edges that are neither straight nor centrally cut ellipses (including circles), it appears that explicit solutions cannot be obtained for the edge extrema: one has to resort to numerical solution of implicit equations or to the calculation of thickness at sufficiently many points around the edge. For the centrally cut ellipse the edge extremal problem turns out to be the eigenvalue problem of linear algebra. In general the thickness extrema at the edge do not lie on the principal meridians of the lens, nor do they lie on meridians that are mutually perpendicular. With minor modification the results apply equally well to the edge extrema for sagitta of a surface.
Effect of the menstrual cycle on corneal curvature
Authors: Oliver Katherine M. , Walsh Glyn , Tomlinson Alan , McFadyen Angus , Hemenger Richard P.
Published: July 2002

The purpose of this research was to determine if a clinically significant variation in corneal curvature occurs with the menstrual cycle. The EyeSys™ Corneal Analysis System™ (CAS) was used to measure corneal curvature of a test group of three normally menstruating female subjects over three cycles and compared with a control group of three males, for three pseudocycles of 28 days. Measurements were taken on days 1, 4, 8, 15 and 22 of each of three menstrual cycles, with four CAS images taken on each day. Four points (along 45, 135, 225 and 315 degrees) were selected for each of rings 1, 3, 6 and 8, and the average curvature for each of these rings was calculated. The results showed that no detectable temporal effect occurred with the menstrual cycle, thus demonstrating that either cyclic variation in corneal topography was too small to be identified by this system or it did not take place.
Spatial frequency dependent observer bias in the measurement of contrast sensitivity
Authors: Woods Russell L.
Published: July 2002

A previously reported spatial frequency dependent change in contrast sensitivity, apparently produced by the psychometric method used, was investigated in two experiments. A relative reduction in the measured contrast sensitivity function at higher spatial frequencies was found when using a simple single staircase procedure, even when all external characteristics of the presentation procedure were the same as a more sophisticated and more reliable psychometric method (adaptive probit estimation). The estimated false‐negative response rate was found to be greater for the single staircase procedure and was greater at a higher spatial frequency, while the false‐positive response rate to interleaved blank presentations did not vary between spatial frequencies and between the two psychometric methods. This supports the suggestion that some subjects, given a knowledge of the psychometric method controlling grating contrast, may adopt different decision criteria at different spatial frequencies.
Calculating relative retinal image sizes of eyes
Authors: Atchison David A.
Published: July 2002

I derive simple formulas which accurately give the relative retinal image sizes of corrected eyes. These are useful in calculations involving anisometropia and/or refractive surgery. Using the formulas, I derive simple equations for particular situations and provide two examples. I compare the formulas with the approach adopted by Applegate and Howland (1993) and Applegate and Chundra (1995) to determine relative retinal image sizes before and after refractive surgery.
The development of the chromatic visual evoked potential
Authors: Rudduck G. A.
Published: July 2002

Evidence exists to suggest that visual function of very young infants is not cortically controlled and may in fact be mediated by a more primitive subcortical system. Visual evoked potentials (VEP) are used widely as a clinical and research tool and in this study the development of the chromatic VEP was investigated. Chromatic vision is a cortical function, hence the presence of a chromatic VEP may suggest the presence of a functioning cortical pathway.

Using pattern reversal stimuli of red and green checks, the presence and morphology of the transient chromatic VEP were assessed. The checkerboards reversed in chromaticity and control of the relative brightness (luminance) of the checks allowed the production of a range of stimuli of different red/green luminance ratios. A black/white stimulus was included in all trails for comparison. VEPs to these stimuli were recorded from 36 infants aged between 1 and 14 weeks post‐term. Fourteen of these infants were then assessed on two further occasions to monitor the longitudinal development of the chromatic VEP. All infants tested demonstrated clear VEPs to achromatic stimuli and to those red/green stimuli that contained luminance information. As the luminance information within the stimuli decreased, the morphology of the wave changed with the major component (P1) becoming diminished and delayed. No VEP could be recorded from any infant less than 7 weeks post‐term at time of testing when using an isoluminant stimulus. In the longitudinal study, all of the infants, who initially demonstrated no response to isoluminant stimuli, did so on reaching their eighth post‐term week.

These results would suggest that those channels responsible for the processing of chromatic information do not function until the eighth post‐term week. During the period prior to this, visual processing takes place via a colour‐insensitive pathway, probably subcortical.
100 years of scleral lenses: where are we now?
Authors: Pullum Kenneth W.
Published: July 2002

The threat of long‐term hypoxic corneal changes together with the complex and unpredictable nature of fenestrated lens fitting have made scleral lens practice unattractive to practitioners. Gas permeability has allowed use of sealed lenses, simplifying the fitting procedures even with advanced pathology.

The case notes for 322 patients seen wearing scleral lenses or assessed for scleral lens fitting were retrospectively analysed to determine the indication for contact lenses, the reasons for scleral lens fitting and the outcome: 47% were for keratoconus or other primary corneal distortions, 19% for postoperative corneal transplant, 12% aphakia, 10% myopia and 10% ocular surface disease. 68% continued to wear RGP sclerals or were fitted or refitted with RGP sclerals, with 19% remaining with PMMA sclerals and 13% discontinuing scleral lens wear or lost to follow‐up.

Scleral lenses remain the lens of choice for a group of contact lens wearers which is relatively small in number but with a high clinical requirement for contact lens correction. The introduction of gas permeable materials has enabled their application for less advanced pathology compared to that possible with PMMA.
Ametropia in Down's syndrome
Authors: Doyle S. , Bullock J. , Gray K. , Spencer A.
Published: July 2002

A matched cohort of 50 individuals (29 male and 21 female) with Down's syndrome in the Manchester area aged 16–18 years was studied by refraction, corneal topography, A‐scan biometry, slit‐lamp examination and orthoptic examination.

1. A linear relationship was found between axial length and spherical equivalent refraction as in the normal population.

2. Forty (80%) of the group had a hypermetropic refraction (mean ±2.46 D, range +0.5 to +7.5 D). Nine (18%) were myopic (mean −2.75 D, range −0.5 to −0.8 D). One (2%) was emmetropic (within ±0.5 D of zero). This indicates a failure of emmetropisation compared to a similar group of normal teenagers of the same age range.

3. There was one (2%) overt keratoconus. Three (6%) had corneal topography with inferior steepening which may be a preclinical keratoconic process.

4. Corneal topography was generally of a regular ‘bow‐tie’ pattern, but there was a high incidence of oblique cylinders with 38% of eyes having their axis outside 10° of the orthogonal axes. 22% had cylinders ‘with the rule’ (±10° to 90°) and 39% had cylinders ‘against the rul’ (±10° of 130°).

5. 8% had amblyopia secondary to childhood squint. 14% had an A‐esophoria.

These findings are discussed.
Paediatric examination spectacles in the assessment of ptosis
Authors: Wood C. M. , Jones C. A. , Loo A.
Published: July 2002

Measuring ptosis in children can be fraught with difficulties as one tries to hold a ruler up to the eye with one hand whilst trying to get the child to look at a toy in the other hand. To overcome this problem, we have designed some decorative spectacles acceptable to the children. These spectacles are lightweight with a vertical measurement in millimetres grid on the lenses. They are colourful, attractive with different cartoon figures. They come in two sizes, which are suitable for children aged between 2 and 6 years. These sizes were chosen by our optician after studying the average sizes of frames worn by children of this age group.

The clinical measurements which can be made are: palpebral fissure height, levator function, margin‐reflex distance and upper lid crease.

By having the children wearing the customised examination spectacles, the examiner has the advantage of having both hands free and so not frightening the children by approaching them with a ruler. These are invaluable in more accurate assessment of ptosis. We have found in our clinic that the majority of children are happy to wear the glasses. We therefore recommend the use of these glasses in the assessment of congenital ptosis.
Objective assessment of spatial vision using the visual evoked potential
Authors: Hadjizenonos C. , Parry N. R. A.
Published: July 2002

Early assessment of the visual function is very important, as many congenital and acquired visual anomalies may lead to permanent visual loss, if not detected and effectively treated within the critical period of visual system development. Any tests employed to assess vision in infants should be objective and give a valid result quickly.

The visual evoked potential (VEP) does not require active responses from the patient. It is recorded in relation to a time‐locked stimulus, typically a grating that reverses in phase (pattern reversal VEPs). Reversal VEPs have been used to estimate visual acuity. A more complete psychophysical description of the visual function is obtained with the contrast sensitivity function (CSF) which determines visibility not only of the finest detail, but also of a wide range of spatial frequencies. However, the VEP amplitude versus spatial frequency function does not accurately reflect the normal CSF when reversing gratings are employed. Reduced VEP responses are obtained in the middle spatial frequency range where stimulus visibility is highest.

Here we show that 16 Hz on‐off modulation of a grating elicits a VEP versus spatial frequency plot which is similar to the CSF in a group of normal adults. When compared with reversal modulation, the test was more predictive of spatial vision defects in a group of amblyopes, thus demonstrating its clinical utility. We have shown that the same technique can be used to monitor age‐related changes in spatial vision in a group of infants whose ages ranged from 5 weeks to 14 months. The test promises to be a useful clinical tool in paediatric ophthalmology.

Supported by a grant from the North Western Regional Health Authority.
An evaluation of vision screening and eye examinations performed on display screen equipment users
Authors: McClure M. , Barnett S. , Jackson A. J.
Published: July 2002

The introduction of regulations governing ‘work with display screen equipment’ has placed a number of important obligations on employers. One of the most widely debated issues concerns an employee's entitlement to ‘an appropriate eye and eyesight test’. Opinions are divided on the relative merits of the new generation of vision screening tests and their relevance within the context of the regulations. In this study the results of 112 full optometric eye examinations performed on ‘regular’ display screen users, 98% of whom had previously failed the City University Computerised Vision Screening Program, are analysed. Comparisons are made between the results of eye examinations and the results of individual vision screening tests which contributed to overall test failure.

Results confirm that those identified by the City University's illiterate E visual acuity screening test as having substandard acuities often required an update to their current spectacle correction. Sixty‐eight percent of those failing vision screening were spectacle wearers and of these 40% were identified as requiring an updated prescription to optimise visual potential. Results also confirm that those failing vision screening on the basis of substandard binocular vision had either a long‐standing history of oculomotor problems or an imbalance of the oculomotor system which may contribute to the presence of visual symptoms. The proportion of those complaining of ocular or visual symptoms, when assessed using the on‐screen questionnaire (69%), was similar to that revealed during the recording of history and symptoms by an optometrist (65%). Interestingly, only 3% of those examined by optometrists were identified as requiring spectacles solely for display screen use. Three percent of those tested were identified as requiring medical referral, using conventional general ophthalmic services referral criteria.

The authors conclude that the City University screening system, when utilised in a coordinated manner within the context of a display screen equipment work‐station risk assessment programme, fulfils both staff and managerial expectations. The utilisation of (on‐site) vision screening identifies those most in need of a full examination and thus allows employers to concentrate financial resources on those most likely to obtain benefit from the provision of professional services.
Prevalence of significant pre‐clinical contrast sensitivity loss in diabetics
Authors: Gilchrist Jim , Pope Richard , Dhanesha Usha , Young Sally , Horsley Clare
Published: July 2002

Aim: To estimate the prevalence of impaired contrast sensitivity (CS) in diabetic patients with normal visual acuity and no clinical detectable retinopathy.

Methods: We measured CS in 75 diabetics with visual acuity of logMAR 0.0 or better, no evidence of retinopathy by direct ophthalmoscopy and fundus photography, and no evidence of cataract. The sample comprised 27 IDDM (15–44 years), and 48 NIDDM (35–71 years). The CS of each patient was measured with sinusoidal gratings at 2, 4 and 8 cdeg−1 using a two‐alternative forced‐choice staircase procedure, and the data were compared with CS values from age‐related non‐diabetic patients. A decision was made for each diabetic that CS was either normal or impaired, based on whether that individual's CS fell more than 2 standard deviations (Criterion A) or 3 standard deviations (Criterion B) below the age‐related non‐diabetic mean value.

Results and conclusions: Estimated proportions, averaged across all spatial frequencies, of diabetic patients with impaired CS were: 28% by Criterion A and 15% by Criterion B. Population estimates (95% confidence intervals) for the prevalence of significant pre‐clinical CS loss in diabetics based on these results are: 18–38% using Criterion A and 7–23% using Criterion B.
Use of visual evoked potentials (VEPs) to investigate mechanisms involved in the reading process
Authors: Greatrex J. C. , Drasdo N.
Published: July 2002

Aim: In this study we have attempted to use VEPs directly to investigate visual mechanisms in the initial stages of the reading process.

Method: The pattern onset mode of stimulation (using a 330 ms presentation time) approximately stimulates the intake of information during reading and accordingly we have adopted this technique to investigate possible responses at several cortical loci which are known to be involved in the reading process. To obtain the best results from localized areas of the cortex, a technique using a 3 cm radius triangular Laplacian derivation was adapted. Right and left hemifoveal responses were recorded with a Medelec Sapphire system, using pattern and letter stimuli. Signals arising from two putative generators, one in the striate cortex (5% up from inion, on the midline) and another possibly from the human homologue of primate area V4 (12.5% up from inion, 17% right), were studied using the 1–3° stimuli to determine contrast responses and spatial selectivity. Four averaged responses from 32 sweeps, filtered (1‐50 Hz), were recorded for contrasts of 80% and 20% and spatial frequencies between 1–22.32 cpd.

Results: The tuning function for checkerboard patterns at 80% contrast for the lateral generator peaked at 2.75 cpd and showed a rapid fall off. The midline response at 80% contrast peaked at 5 cpd and showed a much slower fall off. Responses to letter stimuli were attenuated to approximately 1 μV over V4 and 300 nanovolts from the angular/supramarginal gyri. No significant result was obtained from Wernicke's and Broca's areas.

Conclusions: VEPs may be used to directly investigate the reading process. Further refinement of techniques is necessary to record responses from more specialized areas such as Wernicke's and Broca's areas.
Dual mechanisms of curvature detection
Authors: Davies J. A. , McGraw P. V. , Whitaker D.
Published: July 2002

Purpose: The detection of object curvature is an essential feature of human spatial vision. We investigate the combined effects of contrast and blur on thresholds for curvature detection.

Methods: Horizontally‐oriented line stimuli were displayed on a Macintosh monitor. The lines were windowed in both x‐ and y‐dimensions with a Gaussian profile. We examined a range of x‐ and y‐blur levels by varying the space constant of the relevant Gaussian window, such that stimuli varied in appearance from long, thin lines, to short fat ones. The maximum contrast of the lines varied between 12.5–100%. Subjects were required to indicate whether the line (presented for a duration of 250 msec) was curved upwards or downwards. A method of constant stimuli was used to determine curvature thresholds.

Results: At each level of blur (y‐space constant), threshold remained constant up to a certain line length (x‐space constant) after which they increased. Thresholds also increased with increasing levels of blur. However, performance in all conditions became identical once thresholds were expressed in Weber terms (as a multiple of line length) and stimulus size was specified using a scale‐invariant metric (ratio of line length to blur). When line length is small relative to blur (short, fat lines), thresholds are proportional to blur and are contrast dependent. When line length is large relative to blur (long, thin lines), thresholds become proportional to line length and demonstrate reduced contrast‐dependence.

Conclusion: Combined manipulation of blur and contrast reveals two distinct processes involved in curvature in human vision.

Acknowledgements: Supported by the Visual Research Trust and a Wellcome Trust Vacation Scholarship to JAD.
Age‐related changes in central and peripheral contrast sensitivity
Authors: Latham Keziah , Ferguson Ian , Pacey Ian
Published: July 2002

Purpose: Loss of foveal contrast sensitivity at mid‐high spatial frequencies with increasing age is well documented. The effects of increasing age on peripheral vision are less clear. This study examines the relative effects of age on contrast sensitivity at the fovea and in the periphery, using scaled 2D Gabor patches.

Methods: Five young (age 23.4 ± 2.4 yrs) and five elderly (age 71.9 ± 3.4 yrs) visually normal subjects participated. Stimuli were a series of size‐scaled Gabor patches, each consisting of a constant 0.8 grating cycles per envelope standard deviation. To achieve this, Gaussian envelope size varied inversely with the spatial frequency of the carrier grating. Stimuli were presented at 0° and 10° eccentricity in nasal visual field. Contrast sensitivity was measured using a staircase procedure which converged to a performance level of 79% correct. The subject's task was to correctly identify grating orientation as vertical or horizontal.

Results: For both the young and elderly subjects, contrast sensitivity functions at the two eccentricities are displaced from one another simply by a change in size scale. E2 values, describing the rate of scale change with eccentricity, are 5.8° for young and 8.1° for elderly observers. At the fovea, the elderly show a 0.29 log unit sensitivity loss relative to the young, independent of spatial frequency. At 10° eccentricity, the age‐related loss is 0.19 log units. Inclusion of a 0.5 log unit neutral density filter reduces the sensitivity of young observers by 0.09 log units at the fovea and 0.07 log units at 10°.

Conclusion: Age‐related contrast sensitivity loss occurs predominantly at the fovea. Only part of the loss observed can be attributed to optical factors. Contrast sensitivity is qualitatively the same in the fovea and periphery of young and elderly observers. The only variables affecting the quantitative variations are a scale change dependent on both eccentricity and age, and an age‐related sensitivity loss.