I

“I” selections in the Glossary of Terms for
Anatomy, Physiology & Pathology of the Human Eye


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implant, lens
see intraocular lens

inferior oblique muscle
an extraocular muscle in the orbit, originating from the orbital surface of the maxilla, lateral to the lacrimal groove; the only extrinsic eye muscle not originating in the annulus of Zinn; innervated by the oculomotor nerve (cranial nerve III); extorts, elevates, and abducts the eye (rotates the top of the eye outward, turns the front of the eye upward, and turns the front of the eye outward)

inferior rectus muscle
an extraocular muscle in the orbit, originating in the annulus of Zinn; innervated by the oculomotor nerve (cranial nerve III); depresses, extorts, and adducts the eye (turns the front of the eye downward, rotates the top of the eye outward, and turns the front of the eye inward)

inflammation
a local response to cellular injury that is marked by capillary dilatation, leukocytic infiltration, redness, heat, pain, swelling, and often loss of function; serves as a mechanism initiating the elimination of noxious agents and of damaged tissue

infrared (IR) radiation
see radiation, infrared (IR)

inner nuclear layer
layer of the retina containing the cell bodies of horizontal cells, bipolar cells, amacrine cells, and Müller cells

inner plexiform layer
layer of the retina containing the axons of bipolar cells and amacrine cells and the dendrites of ganglion cells

internal limiting membrane
the innermost layer of the retina, separating the retina from the vitreous humor

internal tunic
see tunica intima

intima, tunica
see tunica intima

intracapsular cataract extraction (ICCE)
removal of the entire cataractous crystalline lens, usually by “cryoextraction” (utilization of a cryoprobe whose refrigerated tip adheres to and freezes tissue of the lens, permitting its removal); no longer the preferred method of cataract extraction, having been replaced by extracapsular cataract extraction (ECCE)

intraocular lens
a small plastic lens, made of a hard plastic (polymethyl methacrylate or PMMA), silicone, acrylic, or hydrogel material, implanted into an eye after cataract surgery to replace crystalline lens which has been removed

intraocular pressure (IOP)
the pressure within the eyeball that gives it a round firm shape, regulated by the rate at which aqueous humor enters and leaves the eye

iodopsin
a violet photosensitive pigment found in the retinal cone photoreceptors that is similar to rhodopsin (in rod photoreceptors) but is more labile; contains photopsin (a protein) and retinene (a light absorbing compound which is derived from Vitamin A); important in photopic vision

irido-corneal angle
the angle formed by the junction of the iris and the cornea

iridocyclitis
inflammation of the iris and the ciliary body

iris
the opaque muscular contractile diaphragm that is suspended in the aqueous humor in front of the lens of the eye; perforated by the pupil and continuous peripherally with the ciliary body; possesses a deeply pigmented posterior surface, which excludes the passage of light except through the pupil, and a colored anterior surface which determines the color of the eye

iris bombe
a condition in which the iris is bowed forward by an accumulation of fluid between the iris and the crystalline lens

iritis
inflammation of the iris; can be caused by systemic diseases (such as rheumatoid arthritis), systemic infections (such as measles, syphilis, and tuberculosis), trauma, or idiopathic (unknown) sources

isotonic
having an osmotic pressure equal to that of the surrounding fluid or medium


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