The effect of colored lenses on the visual evoked response in children with visual stress

Purpose. Some children with visual stress and/or headaches have fewer symptoms when wearing colored lenses. Although subjective reports of improved perception exist, few objective correlates of these effects have been established. Methods. In a pilot study, 10 children who wore Intuitive Colorimeter lenses, and claimed benefit, and two asymptomatic children were tested. Steady-state potentials were measured in response to low contrast patterns modulating at a frequency of 12 Hz. Four viewing conditions were compared: 1) no lens; 2) Colorimeter lens; 3) lens of complementary color; and 4) spectrally neutral lens with similar photopic transmission. Results. The asymptomatic children showed little or no difference between the lens and no lens conditions. When all the symptomatic children were tested together, a similar result was found. However, when the symptomatic children were divided into two groups depending on their symptoms, an interaction emerged. Children with visual stress but no headaches showed the largest amplitude visual evoked potential response in the no lens condition, whereas those children whose symptoms included severe headaches or migraine showed the largest amplitude visual evoked potential response when wearing their prescribed lens. Conclusions. The results suggest that it is possible to measure objective correlates of the beneficial subjective perceptual effects of colored lenses, at least in some children who have a history of migraine or severe headaches.

DENSITY PROFILE, VELOCITY ANISOTROPY, AND LINE-OF-SIGHT EXTERNAL CONVERGENCE OF SLACS GRAVITATIONAL LENSES

Data from 58 strong-lensing events surveyed by the Sloan Lens ACS Survey are used to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of these two estimates inside models with up to three degrees of freedom with respect to the lens density profile, stellar velocity anisotropy, and line-of-sight (LOS) external convergence, which incorporates the effect of the large-scale structure on strong lensing. A Bayesian analysis is employed to estimate the model parameters, evaluate their significance, and compare models. We find that the data favor Jaffe`s light profile over Hernquist`s, but that any particular choice between these two does not change the qualitative conclusions with respect to the features of the system that we investigate. The density profile is compatible with an isothermal, being sightly steeper and having an uncertainty in the logarithmic slope of the order of 5% in models that take into account a prior ignorance on anisotropy and external convergence. We identify a considerable degeneracy between the density profile slope and the anisotropy parameter, which largely increases the uncertainties in the estimates of these parameters, but we encounter no evidence in favor of an anisotropic velocity distribution on average for the whole sample. An LOS external convergence following a prior probability distribution given by cosmology has a small effect on the estimation of the lens density profile, but can increase the dispersion of its value by nearly 40%.

Applying socio-cultural lenses to childhood obesity prevention among African migrants to high-income western countries : the role of acculturation, parenting and family functioning

Migration from third-world and low-income countries to high-income Western countries presents significant challenges for individuals and families, and for health service providers in the receiving societies. Cultural conflicts related to preferred body size/shape and parenting practices, together with differential inter generational rates and styles of acculturation, can affect nutritional and lifestyle choices and be associated with high rates of childhood obesity. Using African cultures as an example, this paper examines these issues. It concludes that, in designing and implementating obesity prevention programmes, health service providers need to understand these factors and how they play out.

Life expectancy of rigid gas permeable and high water content contact lenses

Purpose: The purpose of this study was to evaluate the life expectancy of various rigid gas permeable (RGP) lens materials used on a daily wear basis and to compare these results with the life expectancy of a matched group of soft lens wearers.

Methods: We retrospectively analyzed the records of 600 contact lens wearing patients (300 soft contact lens users and 300 RGP lens users) fit between September 1987 and September 1994. None of the subjects wore lenses on a planned replacement system. For the purposes of the study, RGP lenses were divided into three groups: <40 Dk were considered low-Dk; 41-89 Dk were considered mid-Dk; and >90 Dk were considered high-Dk. All soft lenses were high water content lenses (>60% water content). Lenses were included if they were replaced due to loss, breakage, deposition, or poor wettability but not if replaced because of changes in fit or prescription.

Results; The mean (+SD) life-spans of each lens type in months were 19.9 +/- 17 for low-Dk RGP lenses, 15.9 +/-13.3 for mid-Dk RGP lenses, 9.0+8.2 for high-Dk RGP lenses, and 6.4 +/-5.2 for high water content soft lenses. Statistical analysis using a one-way ANOVA on ranks indicated that these results were statistically significant (P< 0.0001).

Conclusions: Patients should be informed that high-Dk lenses (RGP and soft) provide substantial clinical benefits and that they should expect to replace high-Dk RGP lenses after approximately 6 months. This lends further credence to the use of high-Dk lenses on a planned replacement basis.

Use of silicone hydrogel contact lenses by Australian optometrists

Background: Prior to the launch of silcone hydrogel (Si-H) materials in Australia in 1999, only 1.6 per cent of lenses were prescribed on a continuous wear basis.

Methods: One thousand surveys were distributed randomly to practitioners in Australia during January 2000, 2001 and 2002 (total surveys 3,000). Each anonymous survey requested data about the next 10 patients fitted with contact lenses, including date, age, gender, new fitting or refitting, lens material type, lens design, frequency of replacement, modality of wear, uses per week and care regimen.

Results: Twenty per cent (599) were returned, reporting data on 5,976 fittings. A total of 710 fittings used Si-H contact lenses (11.9 per cent), which represented 18.6 per cent of all soft lens fittings. During the three years, the proportion of practitioners prescribing Si-H lenses increased from 42.2 to 52.5 per cent. In 2000, 43.8 per cent were daily wear, which decreased to 32.2 per cent by 2002. The solution system of choice for daily wear lenses was multipurpose solutions (98.4 per cent); the only alternative was hydrogen peroxide systems. Continuous wear represented 11.7 per cent of all fittings, ofwhich 85.7 per cent were Si-H, 3.0 per cent RGP lenses and 11.3 per cent conventional hydrogels. For continuous wear, 79.0 per cent of fittings were to existing wearers, whereas for daily wear, 59.4 per cent were existing wearers. More males were prescribed Si-H continuous wear contact lenses, while females were more likely to be prescribed Si-H on a daily wear basis.

Discussion: Si-H contact lenses were introduced to the Australian market as a continuous wear contact lens, yet many practitioners use this product for daily wear with multipurpose solutions. By 2002, more practitioners were prescribing Si-H contact lenses for continuous wear than in 2000, suggesting a growing confidence in that product for that mode of wear. A comparison with an earlier survey shows there is an increase in continuous wear from 1.6 per cent to 11.7 per cent over a five-year period.

Trends in Australian contact lenses prescribing 2000

Background:This study was conducted to ascertain current modes of contact lens prescribing in Australia.

Methods:One thousand questionnaires were randomly distributed to proportionate samples of optometrists in each state of Australia. The profession fits the majority of contact lenses in Australia and the sample represents 55 per cent of all optometrists. We requested details of the first 10 patients fitted with contact lenses after receipt of the questionnaire.

Results:We received 224 completed questionnaires, detailing contact lens fits to 2,230 patients. The mean age of the patient group was 32.3 ± 12.9 years and 65 per cent of these were female. Sixty per cent of patients were existing wearers, the remainder being new fits. The data indicated that 94 per cent of new fits were with soft lenses, of which six per cent were for extended wear. For refits 83 per cent were soft lenses and 24 per cent were extended wear. It was clear that the lens of first choice was mid-water-content (52 per cent of all soft lens fits). Only nine per cent of all soft fits were for lenses which were not replaced on a planned basis. The majority of rigid lenses were prescribed using mid-Dk materials (71 per cent). Analysis of solution prescribing indicates that multipurpose products were the most common regimens for planned replacement soft lenses. The percentage of hydrogen peroxide prescribed increased as lens replacement became less frequent.

Conclusions:Non-planned replacement lenses are now rarely prescribed to patients. Extended wear lenses and rigid lenses are prescribed more to existing contact lens wearers. The impact of multifocal lens designs on contact lens prescribing is very small, namely, five per cent of soft contact lenses and eight per cent of rigid lenses, despite 20 per cent of patients being over 45 years of age.