- The iris is the circular, colored curtain of the eye. Its opening forms the pupil. The iris helps regulate the amount of light that enters the eye. The eye has a number of other key components. These include the cornea, pupil, lens, retina, macula, optic nerve and vitreous. The cornea is the clear front window of the eye that transmits and focuses light into the eye. The pupil is the dark aperture in the iris that determines how much light is let into the eye. The lens is the transparent structure inside the eye that focuses light rays onto the retina. The retina is the nerve layer that lines the back of the eye, senses light and creates impulses that travel through the optic nerve to the brain. The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly. The optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain. The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.
* * *The anterior division of the vascular tunic of the eye, a diaphragm, perforated in the center (the pupil), attached peripherally to the scleral spur; it is composed of stroma and a double layer of pigmented retinal epithelium from which are derived the sphincter and dilator muscles of the pupil. SYN: orris. [G. rainbow, the i. of the eye]- i. bicolor a variegated or two-colored i.. SYN: monocular heterochromia.- i. bombé a condition occurring in posterior annular synechia, in which an increase of fluid in the posterior chamber causes a forward bulging of the peripheral i..- plateau i. in angle-closure glaucoma, a flat appearance of the i. rather than a forward convexity.* * *immune reconstitution inflammatory syndrome; Integrated Risk Information System [NLM database]; interleukin regulation of immune system; International Research Information Service; Isostents for Reperfusion Intervention Study
* * *1) the opaque muscular contractile diaphragm that is suspended in the aqueous humor in front of the lens of the eye, is perforated by the pupil and is continuous peripherally with the ciliary body, has a deeply pigmented posterior surface which excludes the entrance of light except through the pupil and a colored anterior surface which determines the color of the eyes2) IRIS DIAPHRAGM
* * *n.the part of the eye that regulates the amount of light that enters. It forms a coloured muscular diaphragm across the front of the lens; light enters through a central opening, the pupil. A ring of muscle round the margin contracts in bright light, causing the pupil to become smaller (see pupillary reflex). In dim light a set of radiating muscles contract and the constricting muscles relax, increasing the size of the pupil. The outer margin of the iris is attached to the ciliary body.
* * *International Research Information Service.
Medical dictionary. 2011.