About the Eye

About the Eye
The human eye is a vital organ that gives us the power of sight and allows us to see the world from a unique perspective. The eye is the sensory organ that gives an individual the most insight about their surroundings. To an optometrist, the eyes provide a non-invasive look at a patient’s vascular system. This allows for early detection and treatment of certain ocular diseases.


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Outer Parts of the Eye

An adult eye is about one inch (or 25 mm) in diameter. It resides in an area of the skull called the orbit, which visibly reveals only one-sixth of the eye. The eyelids, eyelashes and eyebrows are ocular features that protect this exposed area of the eye from strong light, dust particles, and foreign stimuli. The outermost section, or the white part of the eye, is responsible for giving it support and shape. This is known as the sclera. A thin, mucous layer called the conjunctiva, lines the inside of the eyelids and covers the exposed portion of the sclera.

The sclera connects to a clear dome-shaped layer called the cornea, which controls the amount of light that enters the eye. From the cornea, the light is passed through the pupil. The pupil is the dark opening in the centre of the iris, which is pigmented and gives the eye its colour.


Inner Parts of the Eye

Apart from its ability to generate eye colour, the iris functions as a diaphragm, which causes the pupil to expand or contract when adjusting to different light intensities: getting smaller in bright light and larger in dim light.

Located behind the iris, is our natural lens. The lens changes shape to assist the cornea in focusing and directing light onto the retina. The retina is the light-sensitive tissue that lines the inner walls of the eyeball. Most of the eye’s central interior is filled with a gel-like substance, the vitreous, which supports its rigid shape.

Frequently Asked Questions

The eye has many functions to protect our sight.

  • The bony socket of our skull houses the eyeball, wrapped by supportive tissue and muscles that provide a large range of eye movements. 
  • The eyelids protect the surface of our eye from dust and particles, keep our eyes moist by producing and spreading lubricating tears every time we blink, and help control the amount of light entering our eyes. 
  • Eyelashes also protect the surface of our eyes from debris, and certainly are part of the beauty of the human eye! If we lose our eyelashes, dry eye and discomfort can increase. 
  • The conjunctiva is the clear lining overlying the white structure of the eye. It supports blood vessels that carry nutrition over the surface of the eye. This is the lining that tends to flare up with eye allergies, as well as viral and bacterial eye infections. 
  • The sclera is the outermost white part of the eye, which is responsible for giving it support and shape. 
  • Located behind the iris is our natural lens. The lens changes shape to assist the cornea in focusing and directing light onto the retina. 
  • The retina is the light-sensitive tissue that lines the inner walls of the eyeball. 
  • Most of the eye’s central interior is filled with a gel-like substance, known as the vitreous, which supports its rigid shape.

Our eyes work much like a camera, with highly developed structures dedicated to each part of the sophisticated vision system. 

  • Light enters the eye through the cornea, which is the clear dome-shaped front surface of the eye. 
  • The iris is the coloured part of the eye that functions like the diaphragm, which controls how much light enters the eye through the pupil by altering the size of the opening, like the aperture of a camera. The amount of pigment in the cells of the iris is what determines our eye colour.  
  • The crystalline lens is located behind the iris, controlling the focusing ability of the eye. By the ligament-like structure supporting the lens, the eye can change focus between close and far vision. This change in focus from far to near is called accommodation. 
  • Light is focused by the cornea and through the lens to reach the retina, which is the highly sensitive inner lining of the eye. The retina is like the ‘film’ or image sensor of a camera. 
  • The receptors throughout the retina convert the images through the optic nerve, which transmits the image signals through the processing parts of the vision system to land at the visual cortex, the portion of our brain that is dedicated to the sense of sight.

An adult eye is about one inch (or 25 mm) in diameter. It resides in an area of the skull called the orbit, which visibly reveals only one-sixth of the eye. The eyelids, eyelashes and eyebrows are ocular features that protect this exposed area of the eye from strong light, dust particles, and foreign stimuli. The outermost section, or the white part of the eye, is responsible for giving it support and shape. This is known as the sclera. A thin, mucous layer called the conjunctiva lines the inside of the eyelids and covers the exposed portion of the sclera.

The sclera connects to a clear dome-shaped layer called the cornea, which controls the amount of light that enters the eye. From the cornea, the light is passed through the pupil. The pupil is the dark opening in the centre of the iris, which is pigmented and gives the eye its colour.

Apart from its ability to generate eye colour, the iris functions as a diaphragm, which causes the pupil to expand or contract when adjusting to different light intensities: getting smaller in bright light and larger in dim light.

Light information is collected and processed in the retina and then passed in the form of electrical signals. The macula, the central area in the retina, is responsible for our most acute vision. These signals, processed by the retina, are delivered directly to the brain through the optic nerve. Thereafter, the visual information is interpreted by the brain.

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