Eye & Vision
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Eye & Vision
The eye has been called the most complex organ in our body. It's amazing that something so small can have so many working parts. But when you consider how difficult the task of providing vision really is, perhaps it's no wonder after all.
The eye is like a camera. Light comes in through the cornea, a clear cover that is like the glass of a camera's aperture. The amount of light coming in is controlled by the pupil, an opening that opens and closes a little like a camera shutter. The light focuses on the retina, a series of light-sensitive cells lining the back of the eye. The retina acts like camera film, reacting to the incoming light and sending a record of it via the optic nerve to the brain.
Accessory Structures of the Eye: The accessory structures of the eye are the eyelids, eyelashes, eyebrows, the lacrimal (tearing) apparatus and extrinsic eye muscle.
Eyelid An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris.
The adult eyeball measures about 2.5 cm (1 in) in diameter. Of its total surface area, only the anterior one sixth is exposed; the remainder is recessed and protected by the orbit. Anatomically the wall of the eyeball consists of three layer: fibrous tunic vascular tunic retina
The pupil is basically a circular hole in the middle of the iris, which regulates the amount of light that passes through into the retina. In the dark, as the amount of natural light diminishes, the pupil will expand - allowing as much of the little light that there is to pass through. In the day, when everything is brighter, the pupil will constrict to limit the amount that passes through. Surplus: Better Focal Depth (why am I without glasses now ?) Bright Light
Dim Light
Direction of Light
Image Formation: a) The refraction or bending of light by lens and cornea c) Accommodation, the change in shape of the lens e) Constriction or narrowing of the pupil
Crosssection of eye
Ganglion axons Ganglion cell layer Bipolar cell layer Receptor layer
Cross section of retina
Pigmented epithelium
Light
Two types of lightsensitive receptors Cones coneshaped less sensitive operate in high light color vision Rods rodshaped highly sensitive operate at night grayscale vision
cone rod
The eye has been called the most complex organ in our body. It's amazing that something so small can have so many working parts. But when you consider how difficult the task of providing vision really is, perhaps it's no wonder after all.
The eye is like a camera. Light comes in through the cornea, a clear cover that is like the glass of a camera's aperture. The amount of light coming in is controlled by the pupil, an opening that opens and closes a little like a camera shutter. The light focuses on the retina, a series of light-sensitive cells lining the back of the eye. The retina acts like camera film, reacting to the incoming light and sending a record of it via the optic nerve to the brain.
Accessory Structures of the Eye: The accessory structures of the eye are the eyelids, eyelashes, eyebrows, the lacrimal (tearing) apparatus and extrinsic eye muscle.
Eyelid An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris.
The adult eyeball measures about 2.5 cm (1 in) in diameter. Of its total surface area, only the anterior one sixth is exposed; the remainder is recessed and protected by the orbit. Anatomically the wall of the eyeball consists of three layer: fibrous tunic vascular tunic retina
The pupil is basically a circular hole in the middle of the iris, which regulates the amount of light that passes through into the retina. In the dark, as the amount of natural light diminishes, the pupil will expand - allowing as much of the little light that there is to pass through. In the day, when everything is brighter, the pupil will constrict to limit the amount that passes through. Surplus: Better Focal Depth (why am I without glasses now ?) Bright Light
Dim Light
Direction of Light
Image Formation: a) The refraction or bending of light by lens and cornea c) Accommodation, the change in shape of the lens e) Constriction or narrowing of the pupil
Crosssection of eye
Ganglion axons Ganglion cell layer Bipolar cell layer Receptor layer
Cross section of retina
Pigmented epithelium
Light
Two types of lightsensitive receptors Cones coneshaped less sensitive operate in high light color vision Rods rodshaped highly sensitive operate at night grayscale vision
cone rod
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