A narrative review of psychological and educational strategies applied to young children's eating behaviours aimed at reducing obesity risk.

Strategies to reduce risk of obesity by influencing preschool children's eating behaviour are reviewed. The studies are placed in the context of relevant psychological processes, including inherited and acquired preferences, and behavioural traits, such as food neophobia, 'enjoyment of food' and 'satiety responsiveness'. These are important influences on how children respond to feeding practices, as well as predictors of obesity risk. Nevertheless, in young children, food environment and experience are especially important for establishing eating habits and food preferences. Providing information to parents, or to children, on healthy feeding is insufficient. Acceptance of healthy foods can be encouraged by five to ten repeated tastes. Recent evidence suggests rewarding healthy eating can be successful, even for verbal praise alone, but that palatable foods should not be used as rewards for eating. Intake of healthier foods can be promoted by increasing portion size, especially in the beginning of the meal. Parental strategies of pressuring to eat and restriction do not appear to be causally linked to obesity, but are instead primarily responses to children's eating tendencies and weight. Moderate rather than frequent restriction may improve healthy eating in children. Actively positive social modelling by adults and peers can be effective in encouraging healthier eating.

Critical narrative review to identify educational strategies promoting physical activity in preschool.

The aim of this narrative review is critically to evaluate educational strategies promoting physical activity that are used in the preschool setting in the context of obesity prevention programmes. Literature search was conducted between April and August 2010 in English and German databases (PubMED, PsychINFO, PSYNDEX, ERIC, FIS Bildung). Outcomes considered were time and intensity of physical activity, motor skills or measures of body composition. A total of 19 studies were included. Ten studies added physical activity lessons into their curriculum, one study provided more time for free play, eight studies focused on the social and play environment. Studies reporting positive outcomes implemented physical activity sessions that lasted at least 30 min d(-1). Several studies showed that children are most active in the first 10-15 min. The existence or installation of playground markings or fixed play equipment had no effect, whereas the presence or addition of portable play equipment was positively correlated with moderate-to-vigorous physical activity. Teacher training may be a key element for successful interventions. To overcome time constraints, a suggested solution is to integrate physical activity into daily routines and other areas of the preschool curriculum.

Identifying effective behavioural models and behaviour change strategies underpinning preschool- and school-based obesity prevention interventions aimed at 4-6-year-olds: a systematic review.

The aim of this comprehensive systematic review was to identify the most effective behavioural models and behaviour change strategies, underpinning preschool- and school-based interventions aimed at preventing obesity in 4-6-year-olds. Searching was conducted from April 1995 to April 2010 using MEDLINE, EMBASE, CINAHL, PsycINFO and The Cochrane Library. Epidemiological studies relevant to the research question with controlled assignment of participants were included in the review, if they had follow-up periods of 6 months or longer. Outcomes included markers of weight gain; markers of body composition; physical activity behaviour changes and dietary behaviour changes. Twelve studies were included in the review. The most commonly used model was social cognitive theory (SCT)/social learning theory (SLT) either as a single model or in combination with other behavioural models. Studies that used SCT/SLT in the development of the intervention had significant favourable changes in one, or more, outcome measures. In addition, interventions that (i) combined high levels of parental involvement and interactive school-based learning; (ii) targeted physical activity and dietary change; and (iii) included long-term follow-up, appeared most effective. It is suggested that interventions should also be focused on developing children's (and parents') perceived competence at making dietary and physical changes.

Evidence-based recommendations for the development of obesity prevention programs targeted at preschool children.

The ToyBox intervention was developed using an evidence-based approach, using the findings of four reviews. These reviews included three critical and narrative reviews of educational strategies and psychological approaches explaining young children's acquisition and formation of energy-balance related behaviours, and the management of these behaviours, and also a systematic review of behavioural models underpinning school-based interventions in preschool and school settings for the prevention of obesity in children aged 4-6 years. This paper summarises and translates the findings from these reviews into practical evidence based recommendations for researchers and policy-makers to consider when developing and implementing interventions for the prevention of overweight and obesity in young (aged 4-6 years) children. The recommendations focus on two behaviours, physical activity and sedentary behaviour, and healthy eating, and include general recommendations, intervention approaches, interventions content, and simple messages. The review also briefly examines the role that the commercial sector plays in hindering or facilitating attempts to create healthy food environments for children. This paper also recognises that childhood obesity is not an issue for the education sector alone; it needs to be tackled at a multi sectoral level, recognizing the particularly important role of local governments, nongovernment organizations and the media.

Clinical performance of polynomial lenses versus tri-curve lenses. I: initial comfort.

Twenty-two subjects were asked to wear custom-made polynomial back surface design rigid gas permeable (RGP) lenses and conventional tri-curve RGP lenses to compare the initial comfort provided by the two lens designs monocularly and binocularly. Polynomial lenses, based on tri-curve lens fittings, did not provide better initial comfort than tri-curve lenses. The results seem to indicate that an aspheric back surface alone may not play a very important role in the initial comfort of RGP lens wear. The method used to derive the specifications of the polynomial surface may, however, need further modifications to improve its accuracy.

Clinical performance of polynomial lenses versus tri-curve lenses. II: ocular responses.

This study, which was a continuation of the previous one, aimed to determine the subjective and objective responses after wearing polynomial and tri-curve rigid gas permeable (RGP) lenses over a period of 6 months. Subjects were divided into two groups, each of which wore either one of these lens designs and 17 of 22 subjects completed the 6-month study. Subjective responses were assessed by a questionnaire while the objective responses including vision, contrast sensitivity, lens fitting and the corneal integrity, corneal thickness and endothelial cell morphology were assessed by the examiner. There were no significant differences in the subjective ratings, vision, contrast sensitivity and the lens fitting between the two groups. Except for the p-value (p) and the apical radius (r(o)) along the steepest meridian and the coefficient of variation in cell size in the inferior corneal endothelium, there were no significant changes in the palpebral aperture size, the p-value and r(o) along the flattest meridian, corneal thickness and the other endothelial cell variables after the 6-month study period. The poor success and high dropout rates of RGP lens wear in this study stress the importance and need for further investigations of such lenses.

Corneal topography by keratometry.

AIMS: To investigate the ability of a telecentric keratometer to describe the asphericity and curvature of convex ellipsoidal surfaces and human corneas. METHODS: 22 conicoidal convex surfaces and 30 human corneas were examined by conventional keratometry. Additional keratometric measurements were made when the surface was tilted in the horizontal plane relative to the instrument optical axis. This resulted in a series of radius measurements derived from different regions of the surface. These measurements were used to determine the apical radius and the p value of the horizontal meridian of each surface. The results were compared with those derived from measurements using the EyeSys videokeratoscope and form Talysurf analysis. The method was repeated on 30 human corneas and the results compared with those of a videokeratoscope. RESULTS: For the aspheric buttons, the keratometric and the EyeSys results tended to give higher values for both apical radius and the p values than those of the Talysurf analysis. The best agreement was between the Talysurf and the keratometer where the results were not significantly different. For the human corneas, the apical radii were significantly different comparing the keratometer with the videokeratoscope but the p values were not significantly different. CONCLUSION: The keratometric method for assessing curvature and asphericity appears to hold promise as a method for quantifying the corneal topography.

Corneal shape of Hong Kong-Chinese.

Corneal asphericity (the p-value, p) and apical corneal radius (r0) were calculated for 63 Hong Kong-Chinese (39 male and 24 female), using the Topographic Modeling System (TMS-1). The values of p and r0 in, and between, the two principal meridians were compared, and the effects of refractive error and gender were also investigated. The mean +/- SD r0 and p along the flattest meridian of the right eye were 7.82 +/- 0.26 mm and 0.78 +/- 0.12 respectively. The mean +/- SD r0 and p along the steepest meridian of the right eye were 7.64 +/- 0.26 mm and 0.83 +/- 0.15 respectively. Meridional variations were found in r0 and in p. There was no correlation between p and r0 along the two principal meridians. p was not significantly correlated to the refractive error but r0 was. Our results agree with previous findings that while males have longer r0 than females, their p are not significantly different.

The EyeSys videokeratoscopic assessment of apical radius and p-value in the normal human cornea.

The EyeSys videokeratoscope was used to assess the corneal topography in 98 subjects. Scatterplots of distance squared versus radius squared were plotted for the near horizontal and near vertical principal meridians of the two eyes. The regression lines allowed calculation of the surface apical radius and the p-value. The group average apical radius was 7.93 mm (horizontal) and 7.78 mm (vertical). The group average p-value was 0.76 (horizontal) and 0.82 (vertical). Both apical radius and p-value were similar when comparing the two eyes for both the horizontal and the vertical meridians. The two meridians in a single eye, however, had different values for both apical radius and p-value. Male apical radii were longer than those of females but the p-values were the same. There is no apparent association between age and either apical radius or p-value for the subjects used in this study. The asphericity of the cornea does not show any apparent association with corneal curvature in this group of subjects.

Contact lens back surface specification derived from the EyeSys videokeratoscope.

Rigid corneal lenses were designed for 36 subjects using the software available with the EyeSys Corneal Analysis System 2000 (software version 2.00W) and a program from the textbook 'Contact lens Optics and Lens Design' Both alignment and apical clearance designs were investigated. It was found that the EyeSys lenses produced tear layer thickness and axial edge clearance values that were excessive in some cases, especially for flatter corneas. In the case of an alignment mode of fitting, the designs were relatively steep in the back optic zone and flat in the periphery when compared with designs derived from the textbook.

Acuity predictions from visually evoked potential to checkerboard pattern reversal stimuli: the effect of reversal rate.

INTRODUCTION: A pattern reversal stimulus (check size 5.5 minutes of arc) was used to elicit the visually evoked potential (VEP). METHODS: The peak to trough amplitude of the VEP wave was measured and compared to subjective visual acuity (Landolt C). The recordings were made at three, six and 12 pattern reversals per second. RESULTS: The correlation between VEP amplitude and visual acuity was found to decrease at higher temporal frequencies. The decrease is not confined to the use of a television system reversing checkerboard pattern stimulus as suggested by previous workers. DISCUSSION: It may well be concerned with a change in processing of the visual information as could be expected at these higher frequencies.

Comparison of videokeratoscope and autokeratometer measurements on ellipsoid surfaces and human corneas.

BACKGROUND: Various studies have compared the accuracy and repeatability of autokeratometers and videokeratoscopes using calibrated convex surfaces. We investigate the agreement between the Topcon KR-3500 autokeratometer and the EyeSys videokeratoscope on human corneas and calibrated convex surfaces. METHODS: Measurements were obtained from 30 convex ellipsoidal buttons and 20 right eyes of 20 young normal human subjects. Vertex radius and p-values were compared for the two instruments. RESULTS: The two instruments showed excellent agreement on convex buttons. The human data showed no such relationship. For vertex radius, a good level of agreement was obtained only for surfaces whose p-values were near unity. Repeatability was also calculated and was shown to be better with the Topcon autokeratometer than with the EyeSys videokeratoscope. Editing the EyeSys data to encompass the same corneal area as that of the Topcon improved its repeatability, although it did not reach the level of the Topcon autokeratometer. CONCLUSIONS: The Topcon autokeratometer and the EyeSys videokeratoscope showed reasonable agreement for surface topography on convex conicoidal plastic test buttons but not for human corneas. Alterations in the data-capture mechanisms of videokeratoscopes could improve their ability to accurately image paraboloidal surfaces.

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.

The corneal-thickness profile in Hong Kong Chinese.

PURPOSE: This study investigated the topographic corneal thickness in four groups of Hong Kong Chinese. METHODS: The corneal thickness was determined with an ultrasound pachometer mounted on a X-Y plate. A head rest was used to reduce further any movement from the subject during the measurement. After the central cornea was measured, the peripheral cornea was determined on nasal, temporal, superior, and inferior regions, 2 and 5 mm from the corneal center. RESULTS: The corneal thickness was not significantly different between the right and left eyes. For the right eye, there was no significant thickness difference for the four quadrants at a midperipheral and peripheral region, respectively. There was a general thinning of the corneal thickness at all regions from aging but no difference between the genders. CONCLUSION: The corneal thickness in our subjects was similar to that in other studies. The mean central corneal thickness varied from 541.7 (m to 560.8 microm, dependent on age. This study provides some information for the future studies of Chinese corneal thickness.

Validating a "pillar and collar" technique for measuring the edge lift of rigid contact lenses.

PURPOSE: The clinical importance of the edge lift of rigid contact lenses is often neglected, possibly due to previous difficulties in its measurement. A new method of measuring axial edge lift (AEL) and radial edge lift (REL) using standard contact lens verification equipment, such as an optical spherometer, a thickness gauge, and contact lens V gauge, is described. METHODS: The technique was validated for trueness (accuracy) and precision (repeatability) by measuring the edge lift of a number of monocurve lenses, manufactured both with and without a normal edge finish. RESULTS: Edge lift was measured to an accuracy of 0.01 mm. CONCLUSIONS: As long as a mean of eight independent measurements of back optic zone radius (BOZR), sagitta, and one measurement of center thickness are taken, the pillar and collar technique is capable of producing accurate and repeatable measurements of the edge lift of a rigid contact lens.

"Pillar and collar" technique for measuring the axial edge lift of multicurve rigid lenses.

BACKGROUND: The method of using an optical spherometer and a lens thickness gauge, in combination with a pillar and collar, has previously been shown to be repeatable and accurate (to 0.01 mm) in measuring the edge lift of rigid monocurve lenses. PURPOSE: This paper goes on to validate the technique for measurements taken on edge-finished multicurve rigid lenses. METHODS: The axial edge lift (AEL) of a series of multicurve rigid lenses having known values of AEL was measured using an optical spherometer, a thickness gauge, and contact lens V gauge in a similar way as was described in the companion paper. RESULTS: The results show that as long as a correction factor of 0.01 mm is applied, as found in the previous paper, the technique will allow satisfactory verification of the edge lift. CONCLUSIONS: The technique is accurate and reproducible, even in multicurve lens designs, provided that a calibrating correction factor of 0.01 mm is applied to account for methodological error. It will also indirectly allow the accuracy of manufacture of the peripheral curves and diameters of any rigid contact lens to be verified.

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.

The effect of an artificially-elevated intraocular pressure on corneal thickness in Chinese eye.

We measured the central corneal thickness and the applanation intraocular pressure (IOP) on 45 Hong Kong Chinese. There was no obvious relationship between these two parameters, as different from other literatures. It could be due to either a limited number of subjects with a high IOP level (only six subjects with IOP > or = 22 mmHg), or Chinese has a thicker central cornea in general. The mean central cornea of our subjects was thicker (566 +/- 36 microns) than some previous findings. Thirty subjects had their intraocular pressure further increased by adopting a 40 degrees head-down posture. Their IOP and topographic corneal thickness were measured again. There was no significant change in the central corneal thickness even though the IOP was elevated by 11.7 mmHg. However the nasal cornea demonstrated a thinning effect (by some 18 microns) during the IOP elevation but it returned to the pre-inverted level after returning to a sitting posture for 5 min. Further investigation with more corneal regions being measured would be valuable to evaluate the in vivo effect of IOP elevation from glaucoma attack on corneal thickness.

Does the change of anterior chamber depth or/and episcleral venous pressure cause intraocular pressure change in postural variation?

PURPOSE: Previous studies have found that the intraocular pressure (IOP) variation from postural change is due to the obstruction of aqueous outflow by an increase in episcleral venous pressure. This study investigated if any shift of anterior lens position from postural variation would be another contributing factor. METHODS: Thirty-three Chinese subjects were recruited with their IOP and anterior chamber depth (ACD) measured in the sitting, supine, and prone postures. The IOP was measured using a Pulsair 2000 noncontact tonometer and ACD with a Nidek US-2000 EchoScan unit. RESULTS: The highest IOP was obtained in the prone position and this value was significantly different from the IOP obtained in other postures, whereas there was no significant difference in ACD. CONCLUSIONS: Because no significant variation in ACD was demonstrated, the prone and supine IOP variation could be due to something other than the change in lens position. However, a higher IOP in the prone position rather than in the supine position also suggests that it is not merely the episcleral venous pressure causing the IOP change. Investigation of the entire iris profile at different postures would be more informative in future studies.