Children's University Hospital, Temple Street, Dublin, Ireland.
Prog Retin Eye Res. 2012 Nov;31(6):622-60. doi: 10.1016/j.preteyeres.2012.06.004. Epub 2012 Jul 4.
Myopia is the commonest ocular abnormality but as a research topic remains at the margins of mainstream ophthalmology. The concept that most myopes fall into the category of 'physiological myopia' undoubtedly contributes to this position. Yet detailed analysis of epidemiological data linking myopia with a range of ocular pathologies from glaucoma to retinal detachment demonstrates statistically significant disease association in the 0 to -6 D range of 'physiological myopia'. The calculated risks from myopia are comparable to those between hypertension, smoking and cardiovascular disease. In the case of myopic maculopathy and retinal detachment the risks are an order of magnitude greater. This finding highlights the potential benefits of interventions that can limit or prevent myopia progression. Our understanding of the regulatory processes that guide an eye to emmetropia and, conversely how the failure of such mechanisms can lead to refractive errors, is certainly incomplete but has grown enormously in the last few decades. Animal studies, observational clinical studies and more recently randomized clinical trials have demonstrated that the retinal image can influence the eye's growth. To date human intervention trials in myopia progression using optical means have had limited success but have been designed on the basis of simple hypotheses regarding the amount of defocus at the fovea. Recent animal studies, backed by observational clinical studies, have revealed that the mechanisms of optically guided eye growth are influenced by the retinal image across a wide area of the retina and not solely the fovea. Such results necessitate a fundamental shift in how refractive errors are defined. In the context of understanding eye growth a single sphero-cylindrical definition of foveal refraction is insufficient. Instead refractive error must be considered across the curved surface of the retina. This carries the consequence that local retinal image defocus can only be determined once the 3D structure of the viewed scene, off axis performance of the eye and eye shape has been accurately defined. This, in turn, introduces an under-appreciated level of complexity and interaction between the environment, ocular optics and eye shape that needs to be considered when planning and interpreting the results of clinical trials on myopia prevention.
近视是最常见的眼部异常，但作为一个研究课题，它仍然处于主流眼科学的边缘。大多数近视者属于“生理性近视”这一概念无疑对此起到了推波助澜的作用。然而，对将近视与一系列眼部疾病（从青光眼到视网膜脱离）相关联的流行病学数据进行详细分析表明，在“生理性近视”的 0 至-6D 范围内，近视与疾病之间存在统计学显著的关联。近视带来的风险可与高血压、吸烟和心血管疾病带来的风险相媲美。对于近视性黄斑病变和视网膜脱离，风险则要高出一个数量级。这一发现突显了可以限制或预防近视进展的干预措施的潜在益处。我们对引导眼睛正视化的调节过程的理解，以及相反地，这些机制的失败如何导致屈光不正，当然还不完全，但在过去几十年中已经有了巨大的发展。动物研究、观察性临床研究以及最近的随机临床试验已经证明，视网膜图像可以影响眼睛的生长。迄今为止，使用光学手段治疗近视进展的人类干预试验取得的成功有限，但这些试验是基于在黄斑区产生多少离焦的简单假设设计的。最近的动物研究得到了观察性临床研究的支持，这些研究揭示了光学引导的眼球生长机制受到视网膜广泛区域而不仅仅是黄斑区的视网膜图像的影响。这些结果要求我们对屈光不正的定义方式进行根本性的转变。在理解眼球生长的背景下，单一的球镜-柱镜定义黄斑区屈光度是不够的。相反，必须在视网膜的曲面上考虑屈光不正。这意味着只有在准确定义了所观察场景的三维结构、眼球的离轴性能和眼球形状后，才能确定局部视网膜图像的离焦程度。反过来，这又引入了一个未被充分认识的环境、眼球光学和眼球形状之间的复杂程度和相互作用的水平，在规划和解释近视预防临床试验的结果时需要加以考虑。
