松尾 俊彦

We previously revealed the prevalence of strabismus and amblyopia in elementary school children between 6 and 12 years of age in Japan in the year 2003. Questionnaires asking the number of children with different types of strabismus and amblyopia were sent to all elementary schools in Okayama Prefecture in the year 2005, and the results in the year 2005 were compared with those obtained in the year 2003. The number of children covered by the return of questionnaires was 84,619 (74%) of 113,763 total pupils, including grades 1 to 6, in Okayama Prefecture in the year 2005. The total numbers of children with strabismus and amblyopia, including grades 1 to 6, were 844 (0.99%, 95% confidence interval: 0.94-1.06%) and 173 (0.20%, 95% confidence interval: 0.17-0.23%), respectively. The numbers of children with any type of exotropia and any type of esotropia were 524 (0.62%) and 187(0.22%), respectively. In the previous survey conducted in 2003, the number of children covered by the return of questionnaires was 86,531 (76%) of 113,254 total pupils. The total numbers of children with strabismus and amblyopia were 1,112 (1.28%, 95% confidence interval: 1.24-1.36%) and 125 (0.14%, 95% confidence interval: 0.12-0.17%), respectively. The numbers of children with any types of exotropia and esotropia were 602 (0.69) and 245 (0.28%), respectively. The prevalence of strabismus in this large population of Japanese elementary school children was significantly different between the years 2003 and 2005, while the prevalence of amblyopia was similar between the years.

The purpose of this study was to search for chromosomal susceptibility loci for comitant strabismus. Genomic DNA was isolated from 10mL blood taken from each member of 30 nuclear families in which 2 or more siblings are affected by either esotropia or exotropia. A genome-wide search was performed with amplification by polymerase chain reaction of 400 markers in microsatellite regions with approximately 10 cM resolution. For each locus, non-parametric affected sib-pair analysis and non-parametric linkage analysis for multiple pedigrees (Genehunter software, http://linkage.rockefeller.edu/soft/) were used to calculate multipoint lod scores and non-parametric linkage (NPL) scores, respectively. In sib-pair analysis, lod scores showed basically flat lines with several peaks of 0.25 on all chromosomes. In non-parametric linkage analysis for multiple pedigrees, NPL scores showed one peak as high as 1.34 on chromosomes 1, 2, 4, 7, 10, 15, and 16, while 2 such peaks were found on chromosomes 3, 9, 11, 12, 18, and 20. Non-parametric linkage analysis for multiple pedigrees of 30 families with comitant strabismus suggested a number of chromosomal susceptibility loci. Our ongoing study involving a larger number of families will refine the accuracy of statistical analysis to pinpoint susceptibility loci for comitant strabismus.</P>

Photoelectric dyes absorb light and convert photon energy to electric potentials. To test whether these dyes could be used for retinal prostheses, a simple in vitro screening system was developed. Retinal neurons were cultured from the eyes of chick embryos at the 10-day embryonic stage, at which time no retinal photoreceptor cells have yet developed. Intracellular calcium elevation was observed with Fluo-4 in cultured retinal neurons before and after photoelectric dye was applied at varying concentrations to the culture medium. Five of 7 photoelectric dyes tested in this in vitro system induced intracellular calcium elevation in cultured chick retinal neurons. The intracellular calcium elevation generated by the 5 photoelectric dyes was blocked by extracellular calcium depletion in the case of all 5 dyes, and, except for one dye, by the presence of voltage-gated calcium channel blockers. The photoelectric dyes absorbed light under an inverted microscope and stimulated retinal neurons. This simple in vitro system allows the screening of photoelectric dyes which can be used for retinal prostheses.

The purpose of this study was to elucidate the role of extracellular matrix components such as aggrecan, fibronectin, and laminin in the extraocular muscle of patients with strabismus. Resected tissues of the medial rectus muscle of 47 patients with intermittent exotropia obtained during recession-resection surgery were frozen under liquid nitrogen and pulverized by a Freezer/Mill to solubilize the tissue for enzyme immunoassay. The total amounts of aggrecan, fibronectin, and laminin in the resected tissue were correlated with clinical data of patients such as age, exodeviation, and refractive error. The amount of aggrecan decreased significantly with the advance of age (P < 0.0001, Spearman rank correlation test), while the amount of laminin or fibronectin had no correlation with age. Patients with basic type intermittent exotropia showed larger, although not significantly, amounts of aggrecan than those with convergence insufficiency type (P = 0.0538, Mann-Whitney U-test). The amount of aggrecan may be related to motor aspects of intermittent exotropia.

To identify ARIX gene and PHOX2B gene polymorphisms in patients with congenital superior oblique muscle palsy, 3 exons of the ARIX gene and PHOX2B gene were sequenced by genomic DNA amplification with polymerase chain reaction (PCR) and direct sequencing in 31 patients with congenital superior oblique muscle palsy and in 54 normal individuals. A family with a father and one daughter each having congenital superior oblique muscle palsy was also included in this study. Eleven patients with congenital superior oblique muscle palsy had heterozygous nucleotide changes in the ARIX gene, including 4 patients reported on previously. One patient with atrophy of the superior oblique muscle had a new change of T-4G in the promoter region of the ARIX gene. The other 6 patients had a heterozygous nucleotide change of G153A in the 5'-untranslated region (UTR) of the exon 1 of the ARIX gene. These nucleotide changes of the ARIX gene, taken together, had a significant association with congenital superior oblique muscle palsy(P = 0.0022). One patient and 5 patients had heterozygous nucleotide changes of A1106 C and A1121 C in exon 3 of the PHOX2B gene, respectively, while these changes were absent in the normal individuals. Two patients had both the G153A change in the 5'-UTR of exon 1 of the ARIX gene and the A1121 C change in exon 3 of the PHOX2B gene. In conclusion, the polymorphisms of the ARIX gene and PHOX2B gene may be genetic risk factors for the development of congenital superior oblique muscle palsy.

The vision-screening program for 3.5-year-old children in Japan consists of 3 steps:questionnaires and home visual acuity testing, visual acuity testing by nurses and inspection by medical officers at regional Public Health Centers, and examinations by ophthalmologists. In this study, we tested refraction with a hand-held autorefractometer in addition to visual acuity testing and inspection to reveal whether or not autorefraction leads to better detection of eye problems. Autorefraction was performed in 6 consecutive sessions by a single examiner in 265 children at 3.5 years of age who all visited the same center. The children were sent to the third step of examinations by ophthalmologists based on refractive error criteria:3 diopters myopia or 1 diopter hyperopia, and/or 2 diopters astigmatism in either eye, in addition to the current criteria:1) failure in either eye for 0.5 visual acuity at the center, 2) eye-related symptoms revealed by the questionnaires, or 3) eye problems detected by medical officers. Notices to visit ophthalmologists were issued for 64 children (24%), and 37 of those (58%) made the visits, so that documents containing final diagnoses were sent back to the Public Health Office. Of the 64 children, 12 were sent to ophthalmologists based on the current criteria only, 10 based on both the current criteria and the refractive error criteria, and 42 based on the refractive error criteria only. Twelve of the 13 children visiting ophthalmologists by the current criteria had diagnoses such as amblyopia and strabismus. In contrast, 15 of 24 children visiting ophthalmologists by only the refractive error criteria had mainly diagnoses of refractive errors, with no serious problems. In conclusion, autorefraction in addition to visual acuity testing and inspection led to detection of only one additional case of an eye disease at 3.5 years, while tripling the number of children sending to the third-step examination by an ophthalmologist. Thus, from a cost-effectiveness standpoint, autorefraction is not recommended as an additional test when the current system is conducted as designed.

To test transdifferentiation of retinal pigment epithelial (RPE) cells in suspension culture, chick embryonic RPE sheets and dissociated RPE cells were cultured for two months in a non-adherent dish for suspension culture. RPE cells, isolated as a sheet, aggregated immediately and remained the same size with their differentiated characteristics for two months. The presence of basic fibroblast growth factor (bFGF) at concentrations of 10 ng/ml or higher induced the formation of a spherical lentoid structure which was positive for crystallin and bFGF receptor. In contrast, dissociated RPE cells did reaggregate but did not develop the lentoid structure even in the presence of bFGF. The transdifferentiation of RPE cells to the lentoid structure in this study was in contrast to their transdifferentiation to the retina, as reported in a previous study.

To study the expression of the amiloride-sensitive sodium channel, a putative mechano-receptor in the rat eye, reverse transcriptase-polymerase chain reaction and in situ hybridization were done. The gene for the alpha subunit of the amiloride-sensitive sodium channel was shown by polymerase chain reaction to be expressed in mRNA isolated from the whole eye tissue. In situ hybridization demonstrated that the gene was expressed in basal layers of the corneal and conjunctival epithelium, ciliary epithelial cells, lens epithelial cells at the equator, retinal and iris pigment epithelial cells, ganglion cells and cells in the inner and outer nuclear layers of the retina. The results suggest that the amiloride-sensitive sodium channel plays a role in maintaining sodium balance as well as in possible mechanosensation in these ocular tissues.

We analyzed nucleotide changes in 3 genes, ARIX, PHOX2B, and KIF21A, in 6 patients of 3 families with congenital superior oblique muscle palsy. Three exons of ARIX, 3 exons of PHOX2B, and exons 8, 20, and 21 of KIF21A were amplified by polymerase chain reaction from genomic DNA isolated from the peripheral blood. The DNA fragments were directly sequenced in both directions. In 2 different families, a heterozygous nucleotide change, ARIX 153G>A, in the 5’-untranslated region was found in common between a father and daughter with muscle palsy and between a mother and daughter with muscle palsy (Family No. 1 and No. 3). In the other family (Family No. 2), a heterozygous 15-nucleotide deletion, PHOX2B 1124del15, resulting in loss of 5 alanine residues in the alanine repeat of the protein, was found in the daughter with muscle palsy and her father with normal traits, but was not found in the mother with muscle palsy. No KIF21A nucleotide change was found in any patients. The ARIX 153G>A polymorphism might be a genetic risk factor for the development of congenital superior oblique muscle palsy.