Rural-urban differences in myopia prevalence among myopes presenting to Bhutanese retinal clinical services: a 3-year national study.

Purpose: To determine the prevalence and demographic characteristics of myopia among patients presenting to the national vitreo-retinal (VR) services in Bhutan.

Methods: The records of the VR clinic at the apex national referral centre, providing the only VR services in the country, were reviewed to identify all new myopia patients over three years. Thus, we surveyed all referrals nationally.

The epidemics of myopia: Aetiology and prevention.

There is an epidemic of myopia in East and Southeast Asia, with the prevalence of myopia in young adults around 80-90%, and an accompanying high prevalence of high myopia in young adults (10-20%). This may foreshadow an increase in low vision and blindness due to pathological myopia. These two epidemics are linked, since the increasingly early onset of myopia, combined with high progression rates, naturally generates an epidemic of high myopia, with high prevalences of "acquired" high myopia appearing around the age of 11-13.

Correlation between light levels and the development of deprivation myopia.

Purpose: In chicks, daily exposure to bright light (15,000 lux) retards the development of form-deprivation myopia (FDM) by roughly 60%. This study investigated whether higher light intensities increase the amount of protection against FDM, and whether protection and light intensity are correlated. Furthermore, we examined if exposure to bright light can prevent the progression of FDM or whether it affects only the onset of experimental myopia.

Egr-1 mRNA expression is a marker for the direction of mammalian ocular growth.

Purpose: The immediate early gene Egr-1 is thought to form part of the pathway that mediates abnormal ocular growth. This study investigated whether the mRNA expression levels of Egr-1 in a mammalian retina are modulated differentially, depending on the direction of ocular growth.

Methods: To induce accelerated growth and myopia, guinea pigs wore a -5 diopter (D) lens over one eye from 4 to 11 days of age.

Form deprivation and lens-induced myopia: are they different?

In the following point-counterpoint article, internationally-acclaimed myopia researchers were challenged to defend the two opposing sides of the topic defined by the title; their contributions, which appear in the order Point followed by Counterpoint, were peer-reviewed by both the editorial team and an external reviewer. Independently of the invited authors, the named member of the editorial team provided an Introduction and Summary, both of which were reviewed by the other members of the editorial team. By their nature, views expressed in each section of the Point-Counterpoint article are those of the author concerned and may not reflect the views of all of the authors.

Time outdoors and the prevention of myopia.

Recent epidemiological evidence suggests that children who spend more time outdoors are less likely to be, or to become myopic, irrespective of how much near work they do, or whether their parents are myopic. It is currently uncertain if time outdoors also blocks progression of myopia. It has been suggested that the mechanism of the protective effect of time outdoors involves light-stimulated release of dopamine from the retina, since increased dopamine release appears to inhibit increased axial elongation, which is the structural basis of myopia.

The effect of bright light on lens compensation in chicks.

Purpose: It has been shown that sunlight or bright indoor light can inhibit the development of deprivation myopia in chicks. It remains unclear whether light merely acts on deprivation myopia or, more generally, modulates the rate of emmetropization and its set point. This study was conducted to test how bright light interacts with compensation for imposed optical defocus.

Gene expression within the amacrine cell layer of chicks after myopic and hyperopic defocus.

PURPOSE. Ocular growth is regulated locally by signals produced in the retina. The highly heterogeneous nature of the retina may mask important changes in gene expression during global analysis.

Changes in retinal alphaB-crystallin (cryab) RNA transcript levels during periods of altered ocular growth in chickens.

Changes in retinal crystallin gene expression have been implicated in the development of myopia in animal models. We therefore investigated the expression of alphaB-crystallin (cryab) in the chicken retina during periods of increased ocular growth induced by form-deprivation and negative lens-wear, and during periods of decreased ocular growth induced by diffuser removal from previously form-deprived eyes, and plus lens-wear. Cryab RNA transcript levels in the chicken retina were measured using semi-quantitative real-time RT-PCR, at times between 1 h and 10 days after the fitting of diffusers or negative lenses, and at times between 1 h and 3 days following the removal of diffusers from previously form-deprived eyes, or the addition of plus lenses.

Changes in the expression of Pax6 RNA transcripts in the retina during periods of altered ocular growth in chickens.

Genome-wide mapping studies have suggested a possible role for Pax6 in the development of myopia. We therefore investigated the expression of Pax6 RNA transcripts in the chicken retina during periods of increased ocular growth, induced by form-deprivation and negative lens-wear, and during periods of decreased ocular growth, induced by diffuser removal from previously form-deprived eyes, and plus lens-wear. Levels of Pax6 RNA transcripts in the chicken retina were measured using semi-quantitative real-time RT-PCR, at times between 1 h and 10 days after the fitting of diffusers or negative lenses, and at times between 1h and 3 days following the removal of diffusers from previously form-deprived eyes, or the addition of plus lenses.