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Genetic, ethnic affiliation, geographical ancestry. Height, body weight, skin tone, body hair, sexual organs, hair color, hair texture, eye color, eye shape (see epicanthic fold and eyelid variations), nose shape (see nasal bridge), ear shape (see earlobes), body shape; Body and skin variations such as amputations, scars, burns and wounds.
The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
Early racial classification attempts measured surface traits, particularly skin color, hair color and texture, eye color, and head size and shape. (Measurements of the latter through craniometry were repeatedly discredited in the late 19th and mid-20th centuries due to a lack of correlation of phenotypic traits with racial categorization. [ 42 ] )
An epicanthic fold or epicanthus [6] is a skin fold of the upper eyelid that covers the inner corner (medial canthus) of the eye. [3] However, variation occurs in the nature of this feature and the possession of "partial epicanthic folds" or "slight epicanthic folds" is noted in the relevant literature.
Muscles around the iris change the size of the pupil, regulating the amount of light that enters the eye [3] and reducing aberrations when there is enough light. [4] The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera. [5]
Ethnic classifications vary from country to country and are therefore not comparable across countries. While some countries make classifications based on broad ancestry groups or characteristics such as skin color (e.g., the white ethnic category in the United States and some other countries), other countries use various ethnic, cultural ...
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Between birth and age 13 the eye attains its mature size. It weighs 7.5 grams and its volume is roughly 6.5 ml. Along a line through the nodal (central) point of the eye is the optic axis, which is at a slight slant of five degrees toward the nose from the visual axis (i.e., the section going towards the focused point of the fovea).