Inverse Analysis of the Relationship between Ocular Refraction and Birth Month Using Matrix Equations.

Purpose: To find which kind of light exposure and what sensitivity patterns in infancy influence the relationship between ocular refraction and birth month. Methods: We studied 13,757 children whose cycloplegic refraction could be tested during their initial visit to a children's hospital. After dividing subjects into four groups based on refractive degree, the risk ratio for each birth month was calculated from the cases for that month and the results were adjusted using the national birth/month. We then inversely assessed the risk ratio according to the birth month in each group using simply modeling matrix equations. Results: When results were calculated based on the possible effect of the day length, there was a wide variation in the degree of sensitivity depending on the number of months passed since birth at time of investigation, the statistical results falling into insignificant bimodal peaks. In contrast, when based on the assumption the effect was associated with deviations from the yearly average of the day length, far less variation was observed and there was a single natural sensitivity peak at around five months of age in all four refractive groups. Conclusion: Assuming that the peak stage of influence deviation from the yearly average of the day length has on the infant's refraction is at five month, there is a relationship between the refractive degree and the month of birth.

[Long-term changes in the ratio of exotropia to esotropia patients].

PURPOSE: To detect the long-term changes in the ratio of exotropia to esotropia in Japanese patients. METHODS: The published annual reports of 3 children's hospitals in Japan were reviewed with respect to the number of new patients diagnosed with either exotropia or esotropia. The yearly ratios of exotropia to esotropia were calculated from the past 30-year data. The ratios were analyzed by using regression analysis to determine the long-term variability. RESULTS: The ratio of exotropia to esotropia has increased in a parallel manner from less than 1.0 to nearly 2.0 in each of the 3 hospitals. CONCLUSIONS: This gradual increase in the ratio might be attributed to the increasing number of exotropic children who consult a doctor according to the level of development in health care, or might be the result of declining occurrence of accommodative esotropia along with the decreasing number of hyperopic children. Further studies are required to determine the reason for this tendency.

Preparation and certification of the new reference materials; plastics (disk form, JSAC 0621-0625) for determination of mercury using x-ray fluorescent analysis.

The Japan Society for Analytical Chemistry has developed some new plastic certified reference materials (CRMs) for the analysis of mercury in polyester disks using XRF analysis. These CRMs (named as JSAC 0621-0625) were prepared by casting polyesters including a toluene solution of organometallic compounds as a standard. Concentrations of the five levels of mercury ranged from 0 to 250 mg/kg. Homogeneity tests of prepared disks had shown excellent results. Interlaboratory comparison study for the certification was performed by 15 laboratory participants. The z-scores in robust statistical method was applied for the evaluation of outliers. The certified values were assigned after discarding outliers. The uncertainties of certified values were determined as the confidence levels of 95%.