No biological system or structure is likely to be perfectly symmetrical, or have identical right and left forms. This review explores the evidence for eye and visual pathway asymmetry, in health and in disease, and attempts to provide guidance for those studying the structure and function of the visual system, where recognition of symmetry or asymmetry may be essential.

The principal question with regards to asymmetry is not ‘are the eyes the same?’, for some degree of asymmetry is pervasive, but ‘when are they importantly different?’. Knowing if right and left eyes are ‘importantly different’ could have significant consequences for deciding whether right or left eyes are included in an analysis or for examining the association between a phenotype and ocular parameter. The presence of significant asymmetry would also have important implications for the design of normative databases of retinal and optic nerve metrics.

In this review, we highlight not only the universal presence of asymmetry, but provide evidence that some elements of the visual system are inherently more asymmetric than others, pointing to the need for improved normative data to explain sources of asymmetry and their impact on determining associations with genetic, environmental or health-related factors and ultimately in clinical practice.

任何生物系统或结构都不可能是完全对称的，或者具有相同的左右形式。这篇综述探索了健康和疾病中眼和视觉通路不对称的证据，并试图为那些研究视觉系统的结构和功能的人们提供指导，在这些系统中，对称性或非对称性的识别可能是必不可少的。

关于不对称性的主要问题不是“眼睛是否一样？”，因为一定程度的不对称现象普遍存在，而是“什么时候重要地不同？”。知道右眼和左眼是否“显着不同”对于确定分析中是否包括右眼或左眼或检查表型与眼参数之间的关联可能会产生重大后果。显着的不对称性也将对视网膜和视神经指标规范数据库的设计产生重要影响。

在这篇评论中，我们不仅强调普遍存在不对称性，而且提供证据表明视觉系统的某些元素固有地比其他元素更不对称，这表明需要改进的规范性数据来解释不对称性的来源及其对确定关联的影响具有遗传，环境或健康相关因素，并最终在临床实践中出现。