bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of viewing modality and positioning of a car head‐up display (HUD) on response times
Authors: Wolffsohn James S. , Edgar Graham K. , McBrien Neville A. 
Published: March 2003

Purpose: Car HUDs which, unlike those in aircraft, do not usually overlay the outside world, have been positioned in a variety of locations. With the likely increase of HUDs in cars, it is important to establish the optimum location to place the virtual HUD image. The effects of presenting the virtual HUD image to just one eye, or both eyes, while the outside world (traffic lights) is viewed binocularly, were also assessed.Methods: Six subjects responded to changes in simulated traffic lights and a HUD image. Response times and the number of occasions a change was missed were recorded. The HUD was presented at a range of eccentricities of up to 10° horizontally and vertically, relative to the traffic lights. The outside world was always seen in both eyes, with the HUD image being viewed monocularly and binocularly for each of the eccentricities tested.Results: Response times to changes in the outside world view (traffic lights) are significantly faster (P < 0.01) than to changes in the HUD image. Response times to changes in the HUD virtual image and the amount of information missed increased with increasing eccentricity. More information was missed and response times were slower with a monocular HUD than a binocular HUD.Conclusion: The optimum location based on response times and information gathering was found to be approximately 5° diagonally down from the driver's line of sight. A virtual HUD image seen in both eyes is preferable. It is of concern that gross outside world changes are missed when drivers attend to the virtual HUD image and the outside world.
Bias and precision of letter chart threshold estimates: a simulation study
Authors: Gilchrist Jim 
Published: March 2003

Purpose: An ideal letter chart should give accurate (precise and unbiased) estimates of true threshold over the whole range of the chart. Precision and bias may be affected by chart design, scoring procedure and patient response characteristics.Methods: Accuracy of acuity estimates on Bailey‐Lovie (BL) and Snellen (SN) charts were evaluated by computer simulation. Subjects' psychometric acuity functions were modelled using a Weibull function with constant slope and variable threshold level. The model subject gave 500 simulated ‘readings’ of each chart with true thresholds covering the full range of each chart. For each reading a number of scoring procedures were employed based on combinations of: (a) stopping criterion; and (b) estimation rule.Results: Results show that: (1) the BL chart is not necessarily more accurate than SN, but its precision and bias are much more consistent across the threshold range. (2) Accuracy of both charts depends critically on scoring procedure and is affected more by choice of stopping criterion than by choice of estimation rule.Conclusion: A recommended scoring procedure for the Bailey‐Lovie chart based on simulations is: stop reading when 3 errors occur in one line, and estimate threshold as the last letter read correctly.
The influence of hyperglycaemia upon the colour vision of patients with diabetes mellitus
Authors: North R. V. , Cooney O. , Chambers D. , Dolben J. , Owens D. R. 
Published: March 2003

Purpose: To investigate whether an increase in plasma glucose level had an influence upon the colour vision of patients with non‐insulin dependent diabetes mellitus (NIDDM).Methods: A total of 16 patients with NIDDM were investigated, mean age and duration of NIDDM 59.8 and 4.7 years, respectively. The colour vision was assessed every 30 minutes for 4 hours using a Desaturated D15 under three conditions: (1) meal tolerance test (n = 8); (2) stable plasma glucose conditions, i.e. fasting (n = 8); and (3) intravenous glucose tolerance test (n = 8).Results: The total error score does not vary significantly under the three test conditions. The influence of the plasma glucose upon the TES is not significant, even though levels of up to 22.7 mmol/l were recorded.Conclusion: Colour vision does not appear to be influenced by acute increases in plasma glucose concentrations, unlike the deterioration of colour vision found during hypoglycaemia.
Differential effects of luminance and contrast on acuity thresholds across the visual field
Authors: de Lizarduy Jorge Martinez , Whitaker David 
Published: March 2003

Purpose: To investigate the effects of contrast and luminance on acuity thresholds across the visual field. This may shed some light on the important question of why some visual thresholds change only slowly as a function of eccentricity, whereas others fall off extremely quickly.Methods: Resolution thresholds for Gabor patches were measured in the nasal visual field using a modified yes/no staircase procedure. The effect of contrast was examined by changing the physical contrast of the Gabor stimuli between the values of 3.125 and 100%. The effect of luminance was investigated using high contrast Gabor stimuli but varying luminance over 2.7 log units with the use of neutral density filters. Natural pupils were used throughout.Results: The variation in resolution thresholds as a function of eccentricity was well described by the equation T = T0/[+(E/E2)], where T represents threshold, T0 threshold at the fovea, E is eccentricity and E2 is a parameter which describes the rate of decline in performance, representing the eccentricity at which the foveal resolution threshold halves. Changes in contrast resulted in the same logarithmic change in resolution threshold at all eccentricities, leaving the E2 value unchanged. Thresholds were proportional to the logarithm of contrast, and transforming the data in this way accounted for 98% of the variance in the eccentricity and contrast dependent data. Variations in luminance produced quite different effects, with E2 becoming significantly greater as luminance was reduced. At all eccentricities, resolution thresholds were proportional to the logarithm of retinal illuminance, but the gradient of this relationship changed markedly as a function of eccentricity, becoming close to zero at the higher eccentricities studied.Conclusions: The differential effects of contrast and luminance on acuity thresholds can be understood in terms of a pyramidal model of early vision in which reductions in suprathreshold contrast affect the signal by the same amount in all early visual filters, whereas reductions in luminance have a selective effect on smaller visual filters which are more susceptible to quantal noise.
The effect of glare upon visual performance in keratoconus
Authors: Barrett Brendan T. , Gray Lyle S. 
Published: March 2003

Purpose: The irregular optics of keratoconus produce visual deficits not revealed by standard visual acuity measurements. Non‐standard tests, such as low contrast visual acuity, contrast sensitivity measurement and glare sensitivity may provide a fuller description of the visual deficit in keratoconus. The present study investigates the effect of glare upon visual performance in keratoconus using a variety of clinical tests.Methods: One keratoconic subject (aged 28 years), and one visually normal subject (aged 27 years) participated in the study. Monocular log MAR acuities (high and low contrast) and contrast sensitivities (Pelli‐Robson) were measured in the presence and absence of a glare source (Mentor BAT).Results: (1) High contrast acuity was unaffected by glare in the normal subject, but was reduced by 0.20 log units in the keratoconic subject. (2) Glare reduced low contrast acuity by 0.15 log units in the normal subject, and by 0.70 log units in the keratoconic subject. (3) Contrast sensitivity was reduced by 0.30 log units due to glare in the normal subject, and by 0.50 log units in the keratoconic subject.Conclusions: Glare is a significant factor in reducing visual performance in keratoconus. The effects of glare are most pronounced for low contrast visual acuity.
Investigation of retinitis pigmentosa using the multifocal electroretinogram
Authors: Chan H. L. , Brown B. 
Published: March 2003

SummaryRetinitis pigmentosa (RP) patients have pathological changes in both the macula and the periphery, and are known to have abnormal electroretinograms (ERGs). The response densities measured by the multifocal electroretinogram (MERG) in the macula and pericentral retina were greatly reduced in RP. In photopic conditions, some patients had relatively better ERG responses in the macula than in the pericentral retina, and this agreed with the finding that there is usually relatively well‐preserved macular function in RP. In scotopic conditions, both macula and pericentral retina gave poor responses. There was very little increase in response as stimulus luminance increased in RP. The topographical mapping of the MERG results can provide objective, localized assessment of retinal function.
The value of a phenol red impregnated thread for differentiating between the aqueous and non‐aqueous deficient dry eye
Authors: Patel S. , Farrell J. , Blades K. J. , Grierson D. J. 
Published: March 2003

To determine the clinical viability of a phenol red impregnated cotton thread in differentiating between normal, aqueous deficient and non‐aqueous deficient dry eyes.Subjects were recruited on the basis of subjective symptoms, tear stability, rose bengal staining, Schirmer test, conjunctival hyperaemia, patency and number of meibomian glands, presence of mucin strands, appearance of lower tear meniscus. Based on the outcome of the tests, subjects were categorised as either aqueous deficient dry eyes, non‐aqueous dry eyes or normals. Subjects were randomised and a thread was applied by inserting into the lower fornix of the right eye and leaving the thread in place for 120 sec. All data was collected under similar ambient conditions. After gathering all the data, the codes were broken.Mean (±S.D.) thread wetting values were, all dry eyes (n=59) 18.4 mm (5.9). Aqueous deficient dry eyes (n=35), 15.5 mm (4.6). Non‐aqueous deficient dry eyes [n=24], 22.7 mm (5.0). For the normals (n=38), 19.4 mm (5.0). Differences between (i) normals and aqueous deficient dry eyes and (ii) aqueous deficient and non‐aqueous deficient dry eyes were significant (p=0.01). Difference between all dry eyes and normals was not significant. For the aqueous deficient and non‐aqueous deficient dry eyes only, using a cut‐off value of 20 mm the calculated sensitivity and specificity values were 86% and 83% respectively.This cotton thread test can effectively differentiate between aqueous deficient and non‐aqueous deficient dry eye.
Effect of parental myopia on the development of myopia in Hong Kong Chinese
Authors: Edwards M. H. 
Published: March 2003

SummaryA representative sample of Hong Kong Chinese children was followed from 7 to 12 years of age. Refractive error was measured every year (n=123 at age 7 years andn=83 at age 12 years), the axial length of the eye was measured at age 12 years (n=81) and the refractive status of the parents was also determined. Thirty‐one percent of the parents in the sample were myopic and at the age of 12 years 53% of the children were myopic. There was no association between the refractive status of the parents and whether or not a child had myopia. The probability of a 12‐year‐old child with early‐onset myopia having at least one myopic parent was 0.55 and the probability of myopic parents having a myopic child was 0.6. There was no difference in the refractive error or the axial length of 12‐year‐old children according to whether neither, one or both parents were myopic. The genetic influence on myopia may be different in Caucasian and Chinese children, although it is also possible that non‐expression of the genotype in the parents may have confounded the determination of the inheritance pattern of myopia in Hong Kong Chinese children.
A study of the accuracy of corneal reflection pupillometers
Authors: Obstfeld Henri , Chou B. Ralph 
Published: March 2003

SummaryWe studied the accuracy of nine corneal reflection pupillometers made by three manufacturers, because, at the time of investigation, we could not find any information about their accuracy. For this purpose two steel balls separated by spacer bars, were positioned to simulate nominal inter‐pupillary distance (PD) measurements of 55, 60, 65 and 70 mm. Ten measurements of each ‘PD’ for distance vision, were made by two experienced observers, with each instrument. We found that interobserver differences in measurement were clinically insignificant most of the time, although some data sets were significantly different statistically. The most consistent and accurate measurements of PD were achieved with PD 65 mm. The average error in mean value of the measurements for all PD’s, was 2.3 mm, and the average of the standard deviation in our measurements, was 0.26 mm. Significant sources of error were poor eye relief in all instruments evaluated, as well as friction in the scale adjustment mechanism in some instruments. Our findings show that while a given pupillometer may be relied upon to give consistent readings (within the limits of clinically acceptable error), its accuracy should be checked periodically, especially for very small and very large PD measurements.
The influence of contour line size and location on the reproducibility of topographic measurement with the Heidelberg Retina Tomograph
Authors: Roff Emma J. , Hosking Sarah L. , Barnes Derek A. 
Published: March 2003

Summary Background: the recommended contour line (CL) location with the Heidelberg Retina Tomograph (HRT) is on the inner edge of Elschnig's scleral ring. This study investigated HRT parameter reproducibility when: (i) the CL size is altered relative to Elschnig's ring; (ii) the CL is either redrawn or imported between images. Methods: using the HRT, seven 10° images were acquired for 10 normal volunteers and 10 primary open angle glaucoma (POAG) subjects. A CL was drawn on one image for each subject using Elschnig's scleral ring for reference and imported into subsequent images. The CL diameter was then (a) increased by 50 μm; (b) increased by 100 μm; and (c) decreased by 50 μm. To investigate the effect of the method of contour line transfer between images a CL was: (1) defined for one image and imported to 6 subsequent images; (2) drawn separately for each image. Results: parameter variability improved as the size of the CL increased for the normal group relative to Elschnig's ring but was unchanged in the POAG group. The export/import function (method 1) resulted in better parameter reproducibility than the redrawing method for both groups. Conclusions: the exporting and importing function resulted in better parameter variability for both subject groups and should be used for transferring CLs across images for the same subject. Increasing the overall CL size relative to Elschnig's scleral ring improved the reproducibility of the measured parameters in the normal group. No significant difference in parameter variability was observed for the POAG group. This suggests that the reproducibility of HRT images are affected more by the variation in topography between images than change in CL definition.
The effect of conventional CR39 and Fresnel prisms on high and low contrast acuity
Authors: Cheng Desmond , Woo George C. 
Published: March 2003

SummaryThe effect of conventional CR39 and Fresnel prisms on high and low contrast letter acuity was studied. Visual acuity of the fully corrected better eyes of 15 subjects was measured with the high (90%) and low (10%) contrast logMAR letter charts, while they wore prisms of varying power. The results showed that when the power of the conventional CR39 prism and the Fresnel prism reached 10 prism dioptres and 5 prism dioptres, respectively, significant reduction (1 tail t‐test, p<0.05) of the high and low contrast acuity occurred. The Fresnel prism caused a significantly greater acuity reduction than the conventional CR39 prism for powers ranging from 5 to 30 prism dioptres for both contrasts. The rate of acuity reduction with increasing prism power was greater with the low contrast targets than with the high contrast targets for both prisms. In addition, the rate of acuity reduction with increasing prism power was greater with the Fresnel prism than with the conventional CR39 prism for both contrasts. The conventional CR39 prism reduced acuity by a ratio of about 0.8–0.9 of that of the Fresnel prism for powers ranging from 5 to 20 prism dioptres and by about 0.7 for 30 prism dioptres. These ratios applied for both high and low contrast acuity, and therefore were independent of the level of contrast used.
Residual visual functions of guide dog owners in the UK
Authors: Refson K. , Jackson A. J. , Dusoir A. E. , Archer D. B. 
Published: March 2003

SummaryNumbers of guide dog owners (GDOs) in the United Kingdom reached 4700 by the end of 1998. Despite this growing trend, little is known about the nature of their visual loss. This paper reports the results of a national three‐centre investigation into the residual visual functions and ophthalmic conditions of guide dog owners. Random samples of GDOs (Scotland n=82, England n=77, and Northern Ireland n=87) underwent a detailed visual analysis and interview. GDOs had an overall median age of 53 years. Nationally, they make up just 2.4% of the registered blind population. All GDOs were found to have profound loss of visual acuity, contrast sensitivity or visual fields, but only 43% were totally blind. GDOs in Scotland retained higher levels of residual visual function than those in the other two regions. The main causes of visual loss were congenital and early onset degenerative eye disease (retinitis pigmentosa 18%, optic atrophy 10%). Results taken in conjunction with epidemiological registration trends suggest that the past growth in numbers of GDOs is unlikely to be sustainable. Implications for mobility service providers are discussed. It is suggested that increased optometric input and a multidisciplinary approach could assist present and potential guide dog owners.
Corneal surface area: an index of anterior segment growth
Authors: Stone Richard A. , Lin Ton , Sugimoto Reiko , Capehart Cheryl , Maguire Maureen G. , Schmid Gregor F. 
Published: March 2003

SummaryCorneal surface area and perimeter were assessed as novel indices to monitor anterior segment growth, using chicks reared under different photoperiods. We obtained central and mid‐peripheral corneal curvatures using photokeratometry. Anatomical tracings of the anterior corneal surface also were made from freeze‐dried non‐fixed preparations of the anterior segments of the same eyes. Using either photokeratometry or anatomical data, the profile of the anterior corneal surface was fit to a general equation for conical sections; corneal surface area was estimated from surfaces of revolution. Optical techniques modeled the chick cornea as a circle or as an ellipse closely resembling a circle. The anatomical technique, in contrast, modeled the chick corneal profile as a hyperbola. Potential explanations of this discrepancy are discussed. Regardless of which model is evaluated, the corneal surface area and perimeter of two‐week‐old chicks are affected by the photoperiod of rearing. Corneal surface area in particular proved more sensitive than conventional measurements in identifying anterior segment effects of rearing under different photoperiods. Analysis of corneal area may prove useful in evaluating the mechanisms governing anterior segment growth.
Intraocular lens calculation for cataract after previous radial keratotomy
Authors: Stakheev Anton A. 
Published: March 2003

Purpose: The purpose of this study is to discuss the major reasons for the hyperopic shift after cataract surgery following radial keratotomy (RK) and to find potential methods to improve the prediction of intraocular lens power (IOLP). Methods: The results for 18 cataract surgery eyes that had undergone RK were analysed retrospectively. The IOLP was calculated using Haigis, Hoffer Q, and SRK/II formulae with different keratometric measurements. Theoretical IOLP miscalculation (ΔIOLPK) was assessed in order to define the optimal combination of different keratometric parameters and intraocular lens prediction formula. Results: The research revealed a significant temporary hyperopic shift after cataract surgery, the maximum value of which was noted in the first week post‐operatively. Standard keratometers and placido‐topography systems overestimate corneal power after RK. Corneal power overestimation correlates significantly with the spherical equivalent change after RK. Theoretical formulae (Haigis, Hoffer Q) produced the lowest ΔIOLPK using calculated corneal powers derived from spherical equivalent change. Conclusions: Standard autokeratometry significantly overestimates corneal power after RK performed for moderate and high myopia. The use of calculated corneal power and third‐generation theoretical formulae seems to be the most appropriate for IOLP prediction.
HIV‐Associated Disorders in Fat Distribution and Lipid Metabolism
Authors: Abourjaily Paul , Small Franklin 
Published: March 2003

AbstractHIV‐associated lipodystrophy is most commonly characterized by fat redistribution and/or metabolic changes, such as reduced lipid metabolism or impaired glucose tolerance. Despite the growing recognition of this disorder, its causes, characteristics, consequences, and optimal treatment are not fully understood. This review examines the current understanding of the etiology of this syndrome, its acute and long‐term implications for affected HIV‐infected patients, and treatment strategies currently under investigation, including changes in antiretroviral regimens, and the use of insulin‐sensitizing agents, growth hormones, and exercise regimens.
Flavonoids: Diet and Health Relationships
Authors: Prior Ronald L. , Cao Guohua 
Published: March 2003

SummaryFlavonoids and/or phenolic acids are the major components responsible for antioxidant capacity in fruits and vegetables. Recent research has shown that flavonoids are absorbed in humans, although the bioavailablity of these dietary components is not completely clear. Some epidemiological evidence demonstrates a reduced risk of cardio‐ and cerebrovascular diseases in subjects with a high fruit and vegetable (flavonoid) intake. Investigations performed in vitro or in vivo in experimental animals suggest that some of the flavonoids have chemopreventive effects against certain forms of cancers. Flavonoids are potentially beneficial to cardio‐ and cerebrovascular systems due to their antioxidant activity against low density lipoprotein (LDL) oxidation, inhibition of platelet aggregation, and protection against capillary fragility. Flavonoids showed anti‐inflammatory, antiarthritic, and antiallergic activities in vitro, and, thus, may have potential applications in preventing and treating other diseases.