松尾 俊彦

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.

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 purposes of this study were to examine whether body sway is altered immediately after strabismus surgery in children and to find preoperative clinical factors associated with body sway. In a prospective study, body sway was measured on 1-3 days before surgery and on the third day after surgery; for the measurements, computerized static stabilometry was carried out on 28 consecutive patients with strabismus (age range: 3 to 12 years old; mean: 7.4) who underwent strabismus surgery under general anesthesia. The linear length of the sway path (cm), the linear length of the sway path in a particular unit of time (cm/second), and the area of the sway path (cm2), indicative of the extent of body sway, all increased significantly among a total of 28 patients in both conditions of the patient's eyes open and closed, as well as among those in a subgroup of 16 patients with exotropia, after they had undergone strabismus surgery (p < 0.05, Wilcoxon signed ranks test). The center of pressure along the Y axis of orientation from the toe to the heel was found to deviate significantly toward the heel postoperatively, as compared with the preoperative center in the subgroup of 16 patients with exotropia (p < 0.05). Before surgery, 15 patients with no stereoacuity exhibited a greater amount of body sway when their eyes were open than did 13 patients with measurable stereoacuity (p < 0.05, Mann-Whitney U-test). In the subgroup of 16 patients with exotropia when their eyes open, 3 patients with abnormal head posture exhibited more extensive body sway than did 13 patients without abnormal head posture (p < 0.05). Body sway was found to significantly increase immediately after strabismus surgery in children with strabismus. Stereoacuity and abnormal head posture are 2 clinical factors associated with preoperative postural instability.

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.

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.

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.