The scientific reason for sanpaku eyes, specifically where the white part of the eye (sclera) is visible below the iris (lower sanpaku), is often linked to anatomical factors related to vision conditions.
According to a perspective mentioned in a 2020 paper, in many cases, the phenomenon of lower sanpaku is associated with:
- Near-sightedness (Myopia): People with sanpaku eyes, particularly those with sagging lower eyelids, are frequently near-sighted.
- Larger Eye Diameter: Myopic eyes tend to have a larger diameter compared to non-myopic eyes.
- Reduced Lid Support: This increased eye diameter can lead to less structural support for the lower eyelids.
- Lid Sagging: With less support, the lower eyelids can sag or drop slightly.
This sagging of the lower eyelid reveals the white sclera beneath the iris, resulting in the appearance known as sanpaku eyes. Therefore, the scientific explanation, in many instances, boils down to a combination of myopia, increased eye size, and the resulting effect on lower eyelid position.
It's important to note that while this anatomical explanation provides a scientific basis for the appearance, the term "sanpaku" itself carries historical and cultural interpretations outside of ophthalmology.
