Posterior segment
Encyclopedia
The posterior segment is the back two-thirds of the eye
that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina
, choroid
, and optic nerve
.
Some ophthalmologists specialise in the treatment and management of posterior segment disorders and diseases.
The posterior segment is the back two-thirds of the eye that includes the anterior hyaloid membrane and all structures behind it: the vitreous humor, retina
, choroid
, and optic nerve
.
On the anterior side of the lens is the aqueous humour
which is bounded on all sides by the lens
, ciliary body
, suspensory ligaments, and by the cornea. It lets light through without refraction, helps maintain the shape of the eye and suspends the delicate lens. In some animals, the retina contains a reflective layer (the tapetum lucidum
) which increases the amount of light each photosensitive cell perceives, allowing the animal to see better under low light conditions.
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
, choroid
Choroid
The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye , while in the outlying areas it narrows to 0.1 mm...
, and optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
.
Some ophthalmologists specialise in the treatment and management of posterior segment disorders and diseases.
The posterior segment is the back two-thirds of the eye that includes the anterior hyaloid membrane and all structures behind it: the vitreous humor, retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
, choroid
Choroid
The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye , while in the outlying areas it narrows to 0.1 mm...
, and optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
.
On the anterior side of the lens is the aqueous humour
Aqueous humour
The aqueous humour is a clear, gelatinous fluid similar to plasma, but containing low-protein concentrations. It is secreted from the ciliary epithelium, a structure supporting the lens. It is located in the space between the lens and the cornea...
which is bounded on all sides by the lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
, ciliary body
Ciliary body
The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes. It is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. This epithelium produces the aqueous humor. The inner layer is transparent and covers...
, suspensory ligaments, and by the cornea. It lets light through without refraction, helps maintain the shape of the eye and suspends the delicate lens. In some animals, the retina contains a reflective layer (the tapetum lucidum
Tapetum lucidum
The tapetum lucidum is a layer of tissue in the eye of many vertebrate animals....
) which increases the amount of light each photosensitive cell perceives, allowing the animal to see better under low light conditions.
See also
- Anterior segmentAnterior segmentThe anterior segment is the front third of the eye that includes the structures in front of the vitreous humour: the cornea, iris, ciliary body, and lens.Within the anterior segment are two fluid-filled spaces:...
- List of eye diseases and disorders
- Vitreous chamberVitreous chamberThe vitreous chamber or postremal chamber occupies posterior 4/5ths of the eyeball. This chamber of consists of the space between the lens and the retina, and is filled with a transparent gel called the vitreous humor....