The iris

THE IRIS
The iris, visible through the clear cornea as the colored disc inside of the eye, is a thin diaphragm composed mostly of connective tissue and smooth musclefibers. The color, texture and patterns of each person’s iris are unique as a fingerprint.
-Location: The iris is location inside the eye, between the cornea and theinternal crystalline lens. The hole in the middle the pupil and it changes size to regulate the amount of light entering the eye.
-Structure: The iris is 12mm in diameter with acircumference of 37mm. Is composed of four layers: anterior border layer, stroma, dilator papillae muscle and posterior pigment epithelium.
The iris separated theanterior and posterior chambers.
In the middle of a normal iris is the pupil. Is circular and is comparable to the aperture of a camera. The pupil helps regulate the amount oflight passing through the retina, which is at the back of the eye. The pupil may vary from 1 to 8 mm in diameter.
-Blood supply of the iris: The iris has a rich bloodsupply and extensive anastomoses. The arteries have an unusual coiled form to accommodate the variable states of contraction of the iris. Veins lie close to the arteries,with larger veins primarily in the anterior stroma and the smaller veins in the deeper layers.
-Nerve supply: The iris possesses a rich three-dimensional nerve plexus ofmyelinated and non-myelinated nerves.
-Eye color: The color of the eye is determined by the amount of pigment present in the iris structure. There actually are twopigments: melanin and lipochrome, which determine eye color.
Most common eye colors: Brown, hazel, blue and gray.
Rarest eye colors: Amber, green, violet, black and red.