Axial Length
Axial Length Growth And The Risk Of Developing Myopia In European Children
Summary
随着孩子的眼睛的成长，他们的最终眼睛形状和最终的屈光更正受遗传学，环境以及孩子在时间上所做的事情的影响，并且持续的眼睛生长会增加在以后的生活中变得高度近视的风险。能够通过评估儿童对可靠百分位图表的增长来确定其处于什么样的成长阶段，这对于试图预测儿童中近视的未来近视水平以及指导降低眼睛增长率的干预措施很有价值。
This population-based study set out to produce a percentile growth chart for axial length based on the data collected from European children and adults, and in doing so they found a stronger correlation between the refractive error and axial length in myopes compared to the same measurements in emmetropes. A significant relationship was also found in myopes between spherical equivalent refraction and both corneal curvature and axial length. The authors conclude that percentile growth charts of AL can be used as a key predictor for monitoring paediatric eye growth.
临床相关性
- The spherical equivalent (SE) was significantly related to the corneal radius (CR) and, on average, myopic children had steeper CR compared to emmetropes and hyperopes. This was confirmed by the same finding from the adult subjects.
- 与Emmetropes和Hylepes相比，近视儿童的眼睛生长速度更快，近视转移似乎大约发生。9岁。
- 轴向长度findings suggest that if a child seems to be moving up through the percentile groups, there is a good chance they will become myopic.
- 一个孩子年龄在6岁时的良好预测指标，到9岁年龄段时，孩子的百分位数可能是对近视的好预测。
- All of these finding help eye care practitioners identify those with a higher risk of fast progression when we look at the SE, CR and age of the child in practice.
- If we had growth charts to refer to in practice, it makes it easier to demonstrate to parents and patients what track a child’s likely progress could be.
Limitations and future research
Tideman et al were aware of some aspects of their study which may affect their results:
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- The Generation R study (children aged 6-9yrs old) and the Rotterdam study (adults of 57yrs old) were both carried out on the Netherlands, while the ALSPAC study involved 15yr olds in UK. The authors admitted this may have geographical differences.
- There was no data for 20-25yr olds to bridge the gap in between the ages of the cohorts. This could mean that the growth curve trends could be under-estimated for 15yr olds.
- 用于测量AL的仪器有差异。尽管这可能引入了一点差异，但作者认为这不足以改变结果
- 作者还建议，2010年以后的儿童的随访可以揭示他们与研究相比的生长曲线是否陡峭。
- 一个有趣的发现是高度可能与轴向长度生长有关。作者发现6岁老年的身高和Al生长有很强的相关性。对于9年的老年人来说，稍少一些，但仍然是一个显着的相关性。但是，他们发现男孩或女孩的折射错误没有差异，这表明没有性别差异。未来的研究可能会进一步探讨这一点，并确认轴向长度生长是否可能与身高增长率有成比例的联系。
Association Of Axial Length With Risk Of Uncorrectable Visual Impairment For Europeans With Myopia
Summary
在许多发达的近视越来越频繁countries and we now know it isn’t simply a matter of poor vision which we ‘fix’ with spectacles or contact lenses. It can lead to myopic maculopathy, glaucoma, cataract and retinal detachment and having 'high' myopia increases these risks further. These eye conditions can all potentially lead to reduced vision at best and blindness at worst. As myopia increases, the eye’s total axial length has been seen to increase too, and it is this elongation which leaves the eye at risk from ocular pathologies.
The classification of what constitutes ‘high’ myopia can vary. The World Health Organisation (WHO) decided on a threshold of -5.00D and stronger in 2015 (1). For the purposes of their study, Tideman et al classed participants as being highly myopic when they had a spherical equivalent (SE) of -6.00D and an axial length (AXL) of 26mm or more.
This study used cross-sectional data collected from population-based studies undertaken by the Rotterdam study (I, II & III) and the Erasmus Rucphen Study. These results were combined with case-control data from the Myopia Study, with participants across all studies being 25 years or older. The authors wished to explore a link between visual impairment as a result of increased AXL, refractive error and to be able to apply this to the wider population.
临床相关性
It’s all about the risk
- We can see how myopia is likely to be a leading cause of blindness in the near future after the study findings suggest that “visual impairment will increase 7- to 13-fold by 2055 in high-risk areas”.
- We can also be more aware of an individual’s risk when we can see that those with an AXL of 26mm or greater. Those with longer axial length had a higher chance of having myopic-linked vision impairment - this increased from a 3.8% chance if the AXL was less than 26mm to a 25% chance if the AXL was 26mm or longer. An AXL of 30mm or longer was associated with a 90% chance of vision impairment in their lifetime due to complications from myopia.
- Eye Care Professionals are in a prime position to communicate this robust information we have on the risks associated with increased myopia and what their options are to reduce that risk.
- 开始尽早考虑近视管理。
- The participants who were most at risk of visual impairment were in the older age group and they had therefore had longer eyes and higher myopia for a longer time.
- Don’t forget the lower myopes!
- We need to consider all myopes as potentially being at risk of axial elongation and an increasing risk of impairment later in life, as we know from this and other studies that those who ‘only’ have -1.00D refractive error will already have double the risk of myopic maculopathy and posterior sub-capsular cataract compared to an emmetrope.(2)
Limitations and future research
This is a robust analysis taking in the data of more than 15,000 individuals, across multiple studies. The key area for future research is to measure how myopia control interventions for today's generation influence their rates of pathology and vision impairment in the future. This is a very long-term question, as our current generation of children with access to myopia management will need to age another 50-60 years before their outcomes could be compared to the ages analyzed in this paper. To this point, the authors recognized that their calculated risk estimates will become overstated with adoption of (successful) myopia strategies to slow myopia progression.
种族特定研究：作者对不同国家的普遍性有所不同，但这些预测是基于最初从欧洲人收集的价值观，他们意识到这可能不适用于其他种族。他们能够通过使用每个国家 /地区的报告患病率估计来允许这样做。在出版时（2016年），Tideman等人没有意识到任何可能的种族差异，并且感到有信心他们做出了可行的预测。跨不同种族的类似研究将有助于确定这种观察是否成立。
Changes in prevalence:研究揭示,稳定的转变从远视to myopia when they looked at the birth decades of the participants, particularly from 1920 onward, with a higher myopic prevalence in the younger group (25yrs to 60yrs). This suggested that the population had been getting more myopic with time and that the chance of impairment with age was increasing alongside it. The authors predicted that by 2055 there would be a 2 to 3-fold increase risk of visual problems in Europe, a 3 to 5-fold chance in Singapore and a 3 to 6-fold in the Republic of Korea. This was based on their findings where the last study to be included in their analysis was from 2012. It is possible that the likelihood of myopic pathologies could have increased beyond their expectations since then. Further follow-on studies could verify if this has changed significantly.
近视进展
Accommodation Is Unrelated To Myopia Progression In Chinese Myopic Children
Summary
尽管住宿与近视之间的关系已得到广泛研究，但在适应性滞后（不足）是否在近视发展中起作用。提出的机制是，由此产生的触角脱焦刺激轴向长度的生长，以减少焦点的滞后。对此猜想的一个促成因素是采用方法的差异，该方法的作者要解决。
By implementing analysis across a continuous range of accommodation between 0 and 6.00D, and including distance accommodation facility, the authors found no association between both measurement conditions leading them to conclude that lag of accommodation has no influence on rate of myopia progression.
这项研究增加了这样的论点，即适应性滞后对近视的进展没有影响，但是，即使进行了复杂而彻底的分析，对现实世界的观看条件仍然存在许多差异，这意味着陪审团仍在近视进展方面。受住宿滞后的影响。
临床相关性
- An interesting observation from this study was that a faster myopia progression rate at mean study cohort age (0.61D/yr) was found than previously reported by Donovan et al (0.48D/yr).1Leading the authors to suggest thatmore attention should be given to younger myopes whose myopia progresses rapidly and thus more likely to become high myopes in later years.
- Results from this study indicate that accommodation lag has no influence on rate of myopia progression, at least in a Chinese population. However, the results should not be considered as definitive due to differences between study measurement protocols and real world conditions.
Limitations and future research
- 住宿滞后虽然使用精确的系统测量并仔细分析，但在正常条件下不一定会复制实际的住宿滞后：
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- Accommodation lag was measured under monocular conditions, meaning that blur was the only stimulus to accommodation – this does not match real world viewing where binocular fusion also acts as a stimulus to accommodation.
- Accommodation was measured dynamically – the near fixation target focus demand was being continuously moved during the measurement process. This does not replicate static focus stimulus distance, i.e. when reading a book.
- 折射was subjective maximum plus and did not include cycloplegia, which is the current gold standard in a research setting.
- This study involved Chinese children only due to the geographic setting so outcomes cannot be necessarily extrapolated to be representative of children from other ethnicities or countries.
- Most myopia progression data were retrospective, meaning that any potential additional influential factors may not necessarily be similar across all participants. The authors argue that applying a Gompertz function to the data helps alleviate against this potential for error.
- The authors were aware that different times spent concentrating at near wasn’t measured and therefore a conclusion on effect of accommodation-induced hyperopic defocus can’t be deduced.
- Measurements were conducted in a clinical environment with controlled lighting and deliberately chosen working distances doesn’t necessarily translate to how children might read at home.
Prevalence of Myopia
Prevalence Of Myopia Among Disadvantaged Australian Schoolchildren
Summary
This retrospective cross sectional analysis of disadvantaged Australian school children reveals:
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- Lower overall prevalence of myopia than emmetropia and hyperopia
- 大孩子的近视患病率较高
- No change in overall myopia prevalence between 2014 and 2018, but double the prevalence when compared to study data from 1976
临床相关性
- The children included in this study were predominantly from rural areas which in comparison to children living in urban areas conceivably means:
- 花费更多的时间在户外
- Less time spent on digital devices
- 降低教育的期望
- 这项研究仅在时间上捕获了快照的数据，但是它表明，尽管与预期的年龄较小的孩子相比，近视的患病率更高，但近视患病率仍然很低，大多数年龄较大的儿童（14岁和15岁）是emmetropic。
- Study outcomes add further weight to the suggestion that environmental factors such as outdoor lifestyle and early age educational pressures may have an impact on prevalence of myopia.
Limitations and future research
- 进行了非环体视网膜镜检查折射，这可能会偏向更多的近视折射
- The authors indicate that the measured lower prevalence of myopia, compared to that reported in studies on other Australian locations, suggests the need for including questions on socioeconomic status, education and outdoor activity in myopia prevalence studies.
