Human facial features exhibit remarkable diversity, including the spacing between the eyes. This is formally known as interocular distance or interpupillary distance (IPD), which measures the distance between the centers of the pupils. Just as people vary in height or hair color, the distance between one’s eyes naturally differs. Some individuals inherently possess eyes that appear closer together, a characteristic that falls within the broad spectrum of typical human variation.
Understanding Eye Placement Variability
The distance between a person’s eyes naturally varies across the human population. For adults, the average interpupillary distance is approximately 63 millimeters, though a significant portion falls between 50 and 75 millimeters. These measurements are influenced by factors such as age, sex, and ethnic background. Interpupillary distance generally increases from birth through early adulthood, and males typically have a slightly larger distance than females. Therefore, close-set eyes are often simply a reflection of this natural human variation and do not necessarily indicate an underlying health concern.
The Genetics of Eye Spacing
An individual’s eye spacing is significantly influenced by their genetic makeup, which acts as a blueprint for facial development. Genes inherited from parents provide instructions for the growth and formation of all facial structures, including the bony orbits and surrounding soft tissues that determine eye position. This complex trait is not typically controlled by a single gene but rather by the cumulative effect of many different genes working in concert. The observable resemblances within families, such as children having similar eye spacing to their parents or siblings, serve as clear illustrations of this strong genetic influence on facial characteristics.
Developmental Influences on Eye Position
The formation and final positioning of the eyes during prenatal development is a complex and highly orchestrated process. The eyes initially develop more laterally on the embryonic head and gradually migrate towards the midline as the face forms and the skull grows. Small, natural deviations or influences during these critical developmental stages can result in variations in adult eye spacing, contributing to the wide range of appearances seen in the population.
When Eye Spacing Signals Something More
While a narrow interocular distance is often a normal variant, an abnormally decreased distance, termed hypotelorism, can occasionally be a feature of an underlying medical condition. Hypotelorism is typically defined as an interocular distance falling below the 5th percentile for age. In these instances, the close-set eyes are usually accompanied by other distinct physical characteristics or developmental concerns.
Several conditions can present with hypotelorism. Fetal Alcohol Spectrum Disorders (FASD), resulting from prenatal alcohol exposure, are known to cause a range of physical and neurodevelopmental issues, including reduced interpupillary distance and shortened eyelid openings. Certain chromosomal abnormalities, such as Trisomy 13 (Patau syndrome), are frequently associated with hypotelorism and severe midline brain malformations like holoprosencephaly.
Genetic syndromes like Prader-Willi syndrome can also feature a narrow distance between the temples, contributing to the appearance of close-set eyes, alongside other characteristics such as almond-shaped eyes and developmental delays. Additionally, 22q11.2 deletion syndrome, also known as DiGeorge syndrome, can manifest with various facial features. If close-set eyes are observed alongside other developmental delays or unusual physical features, consulting a healthcare professional for a comprehensive evaluation is advisable.