The horizontal size of the exposed depigmented sclera in Caucasians has been previously suggested to be sexually dimorphic, and the significance of this phenomenon remains unclear. Here we build on a previous study and extend it by (i) examining sex differences in other measures of ocular morphology and (ii) exploring the link between eye morphology and biometric markers of facial attractiveness. We used facial photographs of 100 Caucasians (50 men) from Eastern-Central Europe and digitally measured four ocular features. Eye measurements were tested for sex differences and associations with morphometric data on facial averageness and sexual shape dimorphism. We found that sclera surface is more horizontally exposed in men, even though the total surface area is similar in both sexes. We also found that eye fissures are rounder (less rectangular) in women than in men and that irises are brighter in women. We did not find any relationship between the examined eye features and two aspects of facial attractiveness: facial averageness and sexual dimorphism in facial shape. Despite being sexually dimorphic, eye features may be loosely linked with the development of facial sexual ornamentation. The role of sexual selection in the evolution of the observed phenomena is disputable. It is often argued that because of their physical appearance, human eyes are crucial to interpersonal and social interactions. In many aspects, however, the significance of the human eye architecture is unclear. In this study, we examine sex differences in eye morphology and explore the link between ocular features and biometric measures of facial attractiveness in Caucasian men and women. We found that despite being sexually dimorphic, eye features may be loosely linked with biometric markers of facial attractiveness. We argue that the role of sexual selection in the evolution of the observed sex differences is disputable.

中文翻译：

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白种人眼部形态的性别差异：性选择在人眼性别二态性进化中的可疑作用

白种人暴露的脱色巩膜的水平大小以前被认为是两性异形的，这种现象的意义尚不清楚。在这里，我们以先前的研究为基础，并通过（i）检查其他眼部形态测量的性别差异和（ii）探索眼睛形态与面部吸引力生物特征标记之间的联系来扩展它。我们使用了来自东中欧的 100 名白种人（50 名男性）的面部照片，并通过数字方式测量了四个眼部特征。测试眼睛测量的性别差异和与面部平均和性别形状二态性的形态测量数据的关联。我们发现男性的巩膜表面水平暴露得更多，尽管两性的总表面积相似。我们还发现，女性的眼裂比男性更圆（矩形更小），女性的虹膜更亮。我们没有发现所检查的眼睛特征与面部吸引力的两个方面之间存在任何关系：面部平均度和面部形状的性别二态性。尽管是两性异形，但眼睛特征可能与面部性装饰的发展松散相关。性选择在观察到的现象进化中的作用是有争议的。人们经常争辩说，由于人的外表，人眼对于人际交往和社会交往至关重要。然而，在许多方面，人眼结构的重要性尚不清楚。在这项研究中，我们研究了眼睛形态的性别差异，并探讨了白人男性和女性的眼部特征与面部吸引力的生物特征测量之间的联系。我们发现，尽管具有性别二态性，但眼睛特征可能与面部吸引力的生物特征标记松散相关。我们认为，性选择在观察到的性别差异进化中的作用是有争议的。