Introduction: To determine time trends in myopia over a 20-year period in Taiwan, we conducted 5 nationwide surveys pertaining to the ocular refraction of schoolchildren in 1983, 1986, 1990, 1995 and 2000. Materials and Methods: The sampling technique used herein involved the assessment of stratified systematic clusters, with the unweighted myopic rate being repre- sented using data derived from different sectors of the population, such as metropolitan, city, town, and aboriginal. The mean values for the spherical equivalent of the cycloplegic refractive status and the dimension of corneal radii as determined by the autorefractometer were used for the calculation. Results: In our review of 5 nationwide myopia surveys, we found that the mean prevalence of myopia among 7 year olds increased from 5.8% in 1983 to 21% in 2000. At the age of 12, the prevalence of myopia was 36.7% in 1983 increasing to 61% in 2000, corresponding figures for 15-year-olds being 64.2% and 81%, respectively. The prevalence of myopia increased from 74% in 1983 to 84% in 2000 for children aged between 16 and 18 years, and, in addition, the prevalence of high myopia (over -6.0 D) increased from 10.9% in 1983 to 21% of 18-year-old students of Taiwan in 2000. The mean refractive status at the age of 12 deteriorated from -0.48 D in 1983 to -1.45 D in 2000, and from -1.49 D to -2.89 D for children aged 15, whilst for individuals aged 18, it deteriorated from -2.55 D in 1983 to -3.64 D in 2000. The mean ocular refraction began to progress to a myopic condition at the age of 11 in 1983, this becoming an age of 8 years in 2000. There appeared to be significant difference in both the prevalence and the degree of myopia between study participants residing in cities and villages. Conclusions: We conclude that the cause of the relative increasing severity of myopia among the schoolchildren was due to the onset of myopia at a very young, and progressively-decreasing, age over the study period. Thus, to reduce the prevalence and severity of myopia, we should pay more attention to the eye care of pre-schoolchildren. Ann Acad Med Singapore 2004;33:27-33

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Prevalence of myopia in Taiwanese schoolchildren: 1983 to 2000.

Immune surveillance of mucosal surfaces requires the delivery of intact macromolecules and microorganisms across epithelial barriers to organized mucosal lymphoid tissues. Transport, processing and presentation of foreign antigens, as well as local induction and clonal expansion of antigen-specific effector lymphocytes, involves a close collaboration between organized lymphoid tissues and the specialized follicle-associated epithelium. M cells in the follicle-associated epithelium transport foreign macromolecules and microorganisms to antigen-presenting cells within and under the epithelial barrier. Determination of the earliest cellular interactions that occur in and under the follicle-associated epithelium could greatly facilitate the design of effective mucosal vaccines in the future.

Collaboration of epithelial cells with organized mucosal lymphoid tissues

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The vagina as a route for systemic drug delivery.

Chitosan for mucosal vaccination

Although the field of immunology developed in part from the early vaccine studies of Edward Jenner, Louis Pasteur and others, vaccine development had largely become the province of virologists and other microbiologists, because the model for classic vaccines was to isolate the pathogen and prepare a killed or attenuated pathogen vaccine. Only recently has vaccinology returned to the realm of immunology, because a new understanding of immune mechanisms has allowed translation of basic discoveries into vaccine strategies.

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Strategies for designing and optimizing new generation vaccines

The mucosal immune system of mammals consists of an integrated network of lymphoid cells which work in concert with innate host factors to promote host defense. Major mucosal effector immune mechanisms include secretory antibodies, largely of immunoglobulin A (IgA) isotype, cytotoxic T cells, as well as cytokines, chemokines and their receptors. Immunologic unresponsiveness (tolerance) is a key feature of the mucosal immune system, and deliberate vaccination or natural immunization by a mucosal route can effectively induce immune suppression. The diverse compartments located in the aerodigestive and genitourinary tracts and exocrine glands communicate via preferential homing of lymphocytes and antigen-presenting cells. Mucosal administration of antigens may result in the concomitant expression of secretory immunoglobulin A (S-IgA) antibody responses in various mucosal tissues and secretions, and under certain conditions, in the suppression of immune responses. Thus, developing formulations based on efficient delivery of selected antigens/tolerogens, cytokines and adjuvants may impact on the design of future vaccines and of specific immunotherapeutic approaches against diseases associated with untoward immune responses, such as autoimmune disorders, allergic reactions, and tissue-damaging inflammatory reactions triggered by persistent microorganisms.

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Kohlaro Fujiyashi

Papers

Mucosal immunity and tolerance: relevance to vaccine development