Yes, a true "cat eye shape" resulting from a specific genetic disorder is considered rare.
While many people use the term "cat eye" to describe an almond-shaped eye with an upward tilt, the question refers to a specific genetic condition called Cat Eye Syndrome (CES). This condition is different from just having eyes that resemble a cat's in their general shape.
Cat Eye Syndrome (CES)
Cat Eye Syndrome is a rare chromosomal disorder.
- Rarity: The National Organization for Rare Disorders (NORD) estimates that CES occurs in approximately 1 in 50,000 to 150,000 live births.
- Genetic Basis: It is caused by a partial trisomy or tetrasomy of chromosome 22, specifically involving the 22q11 region.
- Characteristics: While the name suggests only eye abnormalities, CES is a complex disorder that can affect many parts of the body. The "cat eye" feature refers to a vertical coloboma of the iris, which gives the pupil an elongated appearance resembling a cat's eye.
- Other possible symptoms: Anal atresia, heart defects, kidney problems, and intellectual disability.
"Cat Eye" as a Descriptive Term
It's important to distinguish between actual Cat Eye Syndrome and the common description of eyes as "cat-like" or "cat eye" in shape. The latter usually refers to:
- Almond-shaped eyes: Eyes that are wider in the middle and taper at the corners.
- Upward tilt: The outer corners of the eyes are slightly higher than the inner corners.
- Epicanthic folds (sometimes): A fold of skin that covers the inner corner of the eye, which is common in people of Asian descent.
These features are simply variations in normal human eye shape and are not related to Cat Eye Syndrome. These types of "cat eyes" are not considered rare, as they are a common and naturally occurring eye shape.
