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Eyes

Last Updated on Jan 02, 2024
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Fastest Reacting Muscle

  • The eyes have the fastest-reacting muscles in the whole body. It contracts in 1/100th of a second (1 Trusted Source
    Strabismus and eye muscle function

    Go to source
    ).
  • The eyes contain more than 50% of the sensory receptors in the human body (2 Trusted Source
    Anatomy, Head and Neck, Eye

    Go to source
    ).

Cornea

  • The cornea is clear and covers the colored iris and pupil.
  • The cornea is the only part of the human body that doesn’t contain blood vessels (3 Trusted Source
    Absence of blood and lymphatic vessels in the developing human cornea

    Go to source
    ).

Eye Blinking

  • The average adult blinks 12 times per minute.
  • When we blink, we close our eyes for 0.3 seconds (4 Trusted Source
    High-speed camera characterization of voluntary eye blinking kinematics

    Go to source
    ).

Size of the Eyeball

  • The diameter of an adult eyeball is around 2.5 cm.
  • The human eyeball is 24.5 mm long (5 Trusted Source
    Variations in Eyeball Diameters of the Healthy Adults

    Go to source
    ).
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Eyelashes

  • Eyelashes grow at a rate of 0.12 to 0.14 mm per day.
  • There are about 90 to 160 lashes on the upper eyelid and 75 to 80 lashes on the lower eyelid.
  • It takes about eight weeks for lashes to grow back after being pulled out (6 Trusted Source
    Anatomy, Head and Neck: Eyelash

    Go to source
    ).

Lens

  • The lens of the human eye is composed of 66% water and 33% protein (7 Trusted Source
    Lens Protein

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    ).

Color Blindness

  • Color blind people find it hard to distinguish colors like green and red (8 Trusted Source
    Types of Color Vision Deficiency

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    ).
  • At birth, everyone is color blind (9 Trusted Source
    Infant color perception: Insight into perceptual development

    Go to source
    ).
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Eye Color

  • Iris determines the color of the eye.
  • Brown is the most common eye color in the world (10 Trusted Source
    Molecular and biochemical mechanisms of human iris color: A comprehensive review

    Go to source
    ).

Retina

  • The retina plays a vital role in vision by capturing the light that enters your eye and translating it into the images you see (11 Trusted Source
    Anatomy, Head and Neck: Eye Retina

    Go to source
    ).

Rods and Cones in the Retina

  • Retinas consist of light-sensitive cells called rods and cones. Rods register the shapes of images and respond to low levels of light while cones respond to bright light and register the color of images (12 Trusted Source
    Molecular bases of rod and cone differences

    Go to source
    ).
  • The retina has about 6 million cones and over 100 million rods.

Tears

  • Newborns will cry out without tears for the first three to six weeks (13 Trusted Source
    How Tears Work

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    ).
  • Tears help protect our eyes from infection and irritation (14 Trusted Source
    Older adults have less tear production. Aging: A Predisposition to Dry Eyes

    Go to source
    ).

References:

  1. Strabismus and eye muscle function - (https://pubmed.ncbi.nlm.nih.gov/17944625/ )
  2. Anatomy, Head and Neck, Eye - (https://www.ncbi.nlm.nih.gov/books/NBK482428/)
  3. Absence of blood and lymphatic vessels in the developing human cornea - (https://pubmed.ncbi.nlm.nih.gov/17077668/)
  4. High-speed camera characterization of voluntary eye blinking kinematics - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4043155/ )
  5. Variations in Eyeball Diameters of the Healthy Adults - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4238270/)
  6. Anatomy, Head and Neck: Eyelash - (https://www.ncbi.nlm.nih.gov/books/NBK537278/)
  7. Lens Protein - (https://www.sciencedirect.com/topics/neuroscience/lens-protein)
  8. Types of Color Vision Deficiency - (https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness/types-color-vision-deficiency)
  9. Infant color perception: Insight into perceptual development - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9314692/)
  10. Molecular and biochemical mechanisms of human iris color: A comprehensive review - (https://pubmed.ncbi.nlm.nih.gov/32488945/)
  11. Anatomy, Head and Neck: Eye Retina - (https://www.ncbi.nlm.nih.gov/books/NBK542332/)
  12. Molecular bases of rod and cone differences - (https://pubmed.ncbi.nlm.nih.gov/34974196/)
  13. How Tears Work - (https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/how-eyes-work/how-tears-work)
  14. Older adults have less tear production. Aging: A Predisposition to Dry Eyes - (https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/how-eyes-work/how-tears-work)
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