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Biomedical subjects

S Pardhan

Publications and source records attributed to S Pardhan.

At least 19 recordsLinked to original sources
PubMed2004

Impact of age and duration on sight-threatening retinopathy in South Asians and Caucasians attending a diabetic clinic.

AIMS: To examine diabetic retinopathy in Asians and Caucasians attending a hospital diabetic clinic and to evaluate the impact of the significant risk factors on the probability of sight-threatening retinopathy. METHODS: A total of 500 diabetic patients (268 Asians, 232 Caucasians) who attended a diabetic clinic within a defined time period were examined for severity of diabetic retinopathy. The existence of sight-threatening retinopathy (STR) was compared in the two groups. Significant risk factors such as age, duration and hypertension were analysed against the probability of STR in each of the two races. RESULTS: Asians demonstrated significantly higher rates of STR. Univariate analysis showed age, duration, race, gender, and insulin-requiring status to be significantly associated with STR. Multivariate logistic regression showed a significant association of STR with race, age and duration of diabetes, with no significant interaction effects between variables. The logistic regression model predicted STR in Asians to be matched to that in Caucasians by a 12.5-year difference factor; that is, Caucasians were older by 12.5 years or had a 12.5-year longer duration than Asians for the same level of STR. CONCLUSIONS: After adjusting for age and duration of diabetes, the probability of STR in Asian diabetic patients attending the diabetic clinics in Bradford is significantly higher than that in Caucasians (odds ratio=3.184, P<0.05). The impact of age and duration was significantly higher in patients of South Asian origin compared to Caucasians.

Adult↗
PubMed2004

Knowledge, self-help and socioeconomic factors in South Asian and Caucasian diabetic patients.

AIMS: We carried out a survey of important nonclinical issues including awareness and self-management of diabetes on a group of South Asian and Caucasian patients attending diabetic clinics within a set period. METHODS: A structured questionnaire examined various issues including demographics, perceived knowledge and awareness of diabetes, perceived self-help/support, and psycho-social factors. A total of 500 patients (268 South Asians and 232 Caucasian) took part. RESULTS: Univariate analysis showed significant differences (P<0.05) with various issues including a lower perceived awareness of diabetes and its complications in South Asians, and of the nutritional content of their diet. Asians also appeared to be less worried in the event of missed clinical appointments and if treatment was not strictly adhered to. CONCLUSIONS: The study provides evidence of the inability of health information systems to convey the importance of diabetic control to the Asian population. In order that this important information reaches the required recipients, more assertive and perhaps more culturally acceptable methods need to be explored.

Adult↗
PubMed2003

Binocular recognition summation in the peripheral visual field: contrast and orientation dependence.

Spatial frequency thresholds for recognition were measured for binocular and monocular viewing conditions at two contrast levels (95% and 7%). Measurements were obtained at the fovea and at four different eccentric retinal locations. Each eccentric retinal location was 8 degrees from the fovea, one on the horizontal axis (180 degrees ), and the other three in the superior field on retinal axes of 90 degrees, 45 degrees and 135 degrees. For the superior and horizontal retinal locations, the orientations of the gratings tested were horizontal (180 degrees ) and vertical (90 degrees ). For the retinal points on the oblique axes, the orientations of the gratings were 45 degrees and 135 degrees. Measurements were also obtained at the fovea for all four different grating orientations at both levels of contrast. Recognition threshold was defined as the highest spatial frequency at which luminance gratings were perceived vertically. At the fovea, binocular summation ratios (binocular spatial frequency/monocular spatial frequency) showed no significant differences for gratings of either contrast levels or for any orientation (p>0.05). In the superior periphery, significantly higher summation ratios were shown by low contrast vertical gratings (p<0.05), and in the horizontal periphery by low contrast horizontal gratings (p<0.05). On the oblique axis, low contrast gratings that were parallel to the oblique meridian showed higher summation ratios compared to those at right angles to it. High contrast gratings, at least at 8 degrees eccentricity, did not show this effect. Data suggest that meridional organisation of the retina (e.g. vertical gratings seen maximally in the superior field) occurs for resolution and that it is evidenced closer to the fovea than previously shown.

Adolescent↗
PubMed2002

The clinical characteristics of Asian and Caucasian patients on Bradford's Low Vision Register.

AIM: To analyse the clinical characteristics of patients on the Bradford Low Vision Register with regards to the type (partially sighted or blind), sex, race, causes and age at registration. METHODS: All the data were obtained from the Morley Street Resource Centre, which keeps records of all registrations in the Bradford Metropolitan District. Information including postcode, date of birth, age, gender, ethnic group, degree, date of registration, cause of registration and age at registration were entered into a database. RESULTS: Of all registrations, 64% were blind and 36% were partially sighted. Asians were younger at registration and there were a significantly lower number of females compared to Caucasians. When data were analysed for the different age groups, in the older group of over 65 years, Asians showed significantly more diabetic retinopathy (26.1%) compared to Asians (7.8%), while Caucasians demonstrated significantly more glaucoma (C: 29.3%; A: 17.4%). In the younger age group (<30 years), the leading causes for Asians were retinitis pigmentosa and nystagmus while for Caucasians it was congenital cataracts and optic atrophy. The proportion of Asians registered was significantly lower than expected from the projected population estimates in Bradford. CONCLUSIONS: The study indicates significant differences in the clinical profiles of the two racial groups. The data do not follow the predictions from published population estimates, with Asians, especially females, being under-represented in the register.

Adult↗
PubMed2000

Self-reported eye disease in elderly South Asian subjects from an inner city cluster in Bradford: a small-scale study to investigate knowledge and awareness of ocular disease.

PURPOSE: To investigate various issues relating to eye diseases in a sample of 200 South Asian residents living in an inner city regional cluster in Bradford. METHODS: Door to door interviews were carried out by one investigator who spoke English, Punjabi and Urdu. Visual acuity and pinhole acuity were measured using a portable LogMAR acuity chart. A structured questionnaire investigated various issues including self-reported eye disease, knowledge of eye disease, the effectiveness of various sources for eye-related information, the importance of early detection of eye diseases and the need for adequate control of systemic diseases linked to eye diseases such as diabetes. RESULTS: Data revealed poor knowledge of self-reported eye diseases and of the importance of early detection and inadequate knowledge of the link between the control of systemic disease such as diabetes and ocular complications. Language barrier problems and poor utilisation of available ocular health care services were also evident. CONCLUSIONS: These data, although not exhaustive, give an insight into various factors that affect the ocular health of the South Asian community in Bradford.

Aged↗
PubMed2000

Binocular summation in the fovea and peripheral field of anisometropic amblyopes.

PURPOSE: Binocular performance in the central and peripheral visual fields was compared for normal and anisometropic amblyopes. METHODS: Binocular and monocular thresholds to a light detection task were measured along the four principal meridia in 10 young normal subjects and 10 anisometropic amblyopes using the Humphrey's Visual Field Analyser. Thresholds were obtained at the fovea and at retinal eccentricities of 5 masculine, 10 masculine, 15 masculine, 25 masculine, 40 masculine and 55 masculine on the horizontal, vertical and oblique meridia of 45 masculine and 135 masculine. RESULTS: Binocular summation ratios (binocular sensitivity/ 'best' monocular sensitivity) were calculated for all the eccentricities. In the normal group, the mean binocular summation ratio for the fovea and the peripheral field was not significantly different. In the amblyopic group, subjects showed no or minimal binocular summation in the foveal region but reached normal ratios in the periphery. DISCUSSION: Results are discussed in terms of tolerance to interocular sensitivity differences in the periphery and selective losses in cortical cells.

Adolescent↗
PubMed1999

Binocular and monocular detection of Gabor patches in binocular two-dimensional noise.

Contrast thresholds for detecting sine-wave Gabor patches in two-dimensional externally added random-pixel noise were measured. Thresholds were obtained for monocular and binocular signals in the presence of spatial correlated (identical) and uncorrelated (independent) noise in the two eyes. Measurements were obtained at four different spectral densities of noise (including zero). Thresholds were higher for monocular stimuli than for binocular, and higher in the presence of correlated noise compared to uncorrelated noise. The magnitude of binocular summation, similar in correlated and uncorrelated noise, decreased with increasing noise strength. The independent contributions of internal noise and sampling efficiency to detection were analysed. Sampling efficiencies were higher for binocular than for monocular viewing for both types of noise, with values being higher with uncorrelated noise. Binocular stimuli showed a lower equivalent noise level compared to the mean monocular case for both types of noise.

Contrast Sensitivity↗
PubMed1998

Surface tilt measured with the EyeSys videokeratoscope: influence on corneal asymmetry.

PURPOSE: To investigate whether the apparent corneal asymmetry in the EyeSys videokeratoscope (VK EyeSys Laboratories, Houston, TX) image is a result of the cornea being tilted in relation to the instrument and to examine the possibility of deducing this tilt from a single captured image. METHODS: Videokeratoscopic images were captured with and without a front surface conicoidal contact lens (experiment 1). An image was captured with central fixation followed by image capture with fixation 10 degrees off center. These two images were used to calculate the angle of tilt with central fixation. The approximate tilt of the cornea derived from a single captured image was determined by the use of a mathematical model applied to some of the ring images (experiment 2). Twenty-four subjects were used in each of the above experiments. RESULTS: The mean tilt for the first group of subjects with the contact lens on the cornea was 2.8 degrees, whereas the tilt for the cornea alone was 3.2 degrees (experiment 1). The corneal tilt for the second group of subjects was 3.3 degrees, and the approximate tilt derived from a single captured VK image, using the equation, was 3.2 degrees (experiment 2). CONCLUSIONS: The similarity of the tilt angle with and without the contact lens in place suggests that the apparent asymmetry seen in the VK images of human corneas may be largely an artifact arising from corneal tilt and not nasal/temporal asymmetry. The agreement of the corneal tilt derived from two VK images and the approximate tilt derived from a single image indicates that the latter may offer a quick and convenient way to determine the fixation adjustment required to eliminate corneal tilt.

Artifacts↗
PubMed1997

A comparison of binocular summation in the peripheral visual field in young and older patients.

PURPOSE: To measure binocular and monocular thresholds to a light detection task in order to investigate binocular summation in the central and peripheral visual fields. The study also aims to investigate any differences in the magnitude of binocular summation in young and older subjects with healthy eyes. METHODS: Binocular and monocular thresholds were measured at eccentricities of 0, 5, 15, 25 and 40 degrees nasally and temporally, using the Humphrey Field Analyser. Binocular summation ratios were computed as the binocular sensitivity divided by the "best" monocular sensitivity. RESULTS: Binocular and monocular sensitivities declined with increasing eccentricity. Binocular summation ratios were shown to be significantly higher for the younger group compared to the older group at all eccentricities. CONCLUSIONS: Using this test, the binocular performance is shown to be lower for the older group at all eccentricities. Results are discussed in terms of age-related cortical cell loss and increased monocular sensitivity difference.

Adult↗
PubMed1997

Comparison of a videokeratoscope and an autokeratometer as predictors of the optimum back surface curves of rigid corneal contact lenses.

PURPOSE: To determine the differences in the corneal topography derived using a 16 mire videokerascope and a 2 mire autokeratometer and to examine whether the differences are clinically significant in the contact lens fitting context. METHODS: The right corneas of 20 subjects were measured by an Eyesys videokeratoscope (windows workstation: version 2000 W) and a Topcon Autokeratometer (KR 3500). The corneal vertex radius and p-value were deduced and used to calculate the back surface specifications of a rigid corneal tricurve contact lens design required for an optimal fit on the corneal model. The study was aimed to evaluate the differences in contact lens specifications related to the current British Standards on contact lens tolerances. RESULTS: In general there was good agreement in the lens specification derived from the two instruments. The differences that were present were small and, with the exception of the second back peripheral radius, were within tolerance limits. CONCLUSIONS: The corneal topography was adequately described by the two mire keratometer for the purpose of fitting this particular lens design on the corneas of the 20 subjects examined.

Adolescent↗
PubMed1996

A comparison of sampling efficiency and internal noise level in young and old subjects.

Contrast detection in different levels of external visual noise allows a given loss in contrast sensitivity to be attributed to either an increase in the internal noise of the visual system, a decrease in sampling efficiency, or both. Sampling efficiency indicates how effectively the available stimulus information is utilized by the visual system. The aim of this study is to investigate the effect of normal ageing on sampling efficiency and internal noise. Contrast thresholds for sine-wave gratings of 6 c/deg were measured in the presence of four (including zero) levels of externally added visual noise in young and older healthy observers. Results showed that sampling efficiencies were significantly lower for the older group compared to the younger, while the internal noise showed no significant change. The implications of the data for the relative contribution of the optical and neural systems on visual function loss with ageing are discussed. Our results suggest that the neural system plays a major role in the loss of contrast sensitivity with ageing in normal, healthy eyes.

Adolescent↗
PubMed1996

Extent and effect of surface tilt on the data display of the EyeSys videokeratoscope.

AIMS: This study examined the occurrence, magnitude, and the consequences of a possible tilt between the corneal surface and optical axis of the EyeSys videokeratoscope. METHODS: Initially, a theoretical model was developed to calculate the angle of tilt. The predictions of the model were verified empirically using a convex conicoid surface and were found to predict the tilt to within 0.5 degree of the actual tilt. The likely effects of the tilt on the corneal power were also examined. The angle of tilt was then measured on the human cornea and the effect of neutralising the tilt on the videokeratoscopic data display was observed. RESULTS: The angle of tilt was found to lie between 1 degree and 6 degrees in a temporal direction. CONCLUSION: When the corneal tilt on the human subjects was neutralised, then a reduction in the nasal/temporal asymmetry was observed.

Cornea↗
PubMed1996

A comparison of binocular summation in young and older patients.

Binocular and monocular contrast sensitivities were measured at two spatial frequencies of 1 and 6 c/deg in 8 young (mean age 22.6 +/- 3.8 years) and 18 older subjects with normal healthy eyes (mean age 58.4 +/- 7.3 years). Data were analysed as binocular summation ratios defined as binocular CS/"best eye' CS. Binocular summation ratios were higher for the younger group (1.46 and 1.48 for 1 and 6 c/deg respectively) compared to the older group who demonstrated a spatial frequency dependence (1.31 and 1.13 at 1 c/deg and 6 c/deg respectively). The results are discussed in terms of age-related cortical cell loss and increased monocular sensitivity differences between the two eyes.

Adult↗
PubMed1995

Accuracy and repeatability of the Topcon K-3500 autokeratometer on calibrated convex surfaces.

The vertex (apical) radius and the p value of 30 conicoidal convex surface plastic buttons were measured using the Topcon KR-3500 autokeratometer. The vertex radius was found using the equations derived in the introduction. The results were compared to those derived by the Form Talysurf technique, which was considered to give a precise indication of both the vertex radius and p value. The results revealed a good agreement between the two methods of measurement. The autokeratometer displayed a tendency to underread the vertex radius, compared to the Talysurf result, but the maximum difference was 0.02 mm (95% confidence interval). For the p value, the autokeratometer could over- or underread with a maximum difference of 0.035. The largest coefficient of repeatability for the two observers using the Topcon autokeratometer was found to be 0.033 mm for vertex radius and 0.068 for the p value.

Calibration↗
PubMed1995

Fixation disparity and near visual acuity.

Twenty patients having associated heterophoria values of 2 delta and greater, as recorded with a Mallett unit, had their near monocular and binocular visual acuities measured. In the latter case, measurements were taken both with the associated heterophoria corrected by prisms and without prism correction. Bradford Near Vision charts, specially designed to measure visual acuity at near in seconds of arc, were used in the acuity measurement. The improvement of binocular acuity compared with monocular acuity was less than would occur in normal subjects without associated heterophorias. When the associated heterophorias were corrected with prisms the improvement in binocular over monocular acuity was similar to that found in normal subjects, with zero associated heterophoria readings.

Adolescent↗
PubMed1995

Sport-related eye trauma: a survey of the presentation of eye injuries to a casualty clinic and the use of protective eye-wear.

The study investigated the workload offered by sport-related trauma to a busy casualty clinic and was carried out in two parts. The first part concerned compiling information about sport-related injuries presenting in 1 year to the outpatient eye clinic at Bradford Royal Infirmary. The second part attempted to investigate the awareness and the use of eye-protectors for squash by the student community of Bradford University, using a questionnaire. The sport-related injuries presenting to the casualty department were classified according to the sport involved. Analysis of the data shows that racquet sports, namely tennis, badminton and squash, jointly formed the highest percentage of presentations. In the case of squash and tennis injuries, follow-up treatment and/or admission to hospital was required in 100% of cases. These injuries could be reduced by wearing adequate eye-protectors. The questionnaire survey showed that only 9% of the squash players wore eye protection whilst playing, of whom 3.37% of the total had suffered lacerating injuries previously. Comparison with previous studies indicates that the pattern of eye injuries presenting to casualty departments, and the awareness of the general public concerning the use of eye-protectors, has not altered in recent years. Unless steps are taken, in terms either of mandatory use of eye-protectors and/or of educating the general public on the possible devastating effects of injury, these preventable injuries will continue to burden already overworked hospital casualty departments, draining both resources and expertise.

Athletic Injuries↗
PubMed1994

Effect of fixation disparity on distance binocular visual acuity.

Subjects with appreciable values (2 delta and greater) of associated 'phoria, as measured by a Mallett unit, had their distance monocular and binocular visual acuities measured. In the latter case measurements were taken both with the associated 'phoria corrected by prisms and without such a correction. The improvement in binocular acuity compared to monocular acuity was less than would occur in normal subjects with minimal associated 'phorias although the improvement differed accordingly as to whether the readings were eso- or exo-in mature. When the associated 'phorias were corrected with prisms the improvement in binocular over monocular visual acuity was similar to that found in normal subjects.

Adult↗