Introduction:
Foetal alcohol syndrome (FAS) is a serious condition resulting from prenatal alcohol exposure, often characterised by distinct facial features. The goal of this study is to demonstrate the need to develop reference distributions for the width of the palpebral fissure in the Polish population, as this is one of the most important characteristics applicable to the diagnostic FAS syndrome.

Material and methods:
The research involved 210 children (102 girls and 108 boys) aged 3–16 years (mean age 9.57 years). The palpebral fissure lengths were measured using a computerised method applied to digital photographs. The images were labelled solely by the child’s sex and birth date. The study participants were primarily recruited from patients admitted to the Children’s Memorial Health Institute and their siblings. An additional sample of 38 children was recruited from scientific events. The study took place between 2019–2023.

Results:
The measurements were grouped into two-year age categories. A statistical hypothesis test was performed to assess the assumption that the palpebral fissure length (PFL) of the right eye is equal to that of the left eye. The mean values of PFL were classified by age and gender groups. The analysis revealed that PFL increases with age, and there is a slight, though not statistically significant, difference between boys and girls in each age group

Conclusions:
These data have important implications for the accurate diagnosis and management of FAS and related disorders. By addressing the identified limitations and expanding research efforts, future studies can build on this foundation, ultimately enhancing clinical outcomes and supporting public health initiatives.