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Chapter 5
The Eye
| Term | Definition |
|---|---|
| choroid | vascular layer beneath the sclera that provides nourishment to the outer portion of the retina |
| ciliary body | ring of tissue behind the peripheal iris that is composed of ciliary muscle and ciliary processes |
| ciliary muscle | smooth muscle portion of the ciliary body, which contracts to assist in near vision |
| ciliary processes | epithelial tissue folds on the inner surface of the ciliary body that secrete aqueous humor |
| fovea centralis | pinpoint depression in the center of the macula lutea that is the site of sharpest vision |
| fundus | interior surface of the eyeball, including the retina, optic disc, macula lutea, and posterior pole (curvature at the back of the eye) |
| macula lutea | central region of the retina; responsible for central vision; yellow pigment provides its color |
| optic disc | exit site of retinal nerve fibers as well as entrance point for retinal arteries and exit point for retinal veins |
| optic nerve | nerve responsible for carrying impulses for the sense of sight from the retina to the brain |
| posterior chamber | space between the back of the iris and the front of the vitreous chamber; filled with aqueous humor |
| retina | innermost layer that perceives and transmits light to the optic nerve |
| cones | cone-shaped cells within the retina that are color sensitive and respond to bright light |
| rods | rod-shaped cells within the retina that respond to dim light |
| sclera | tough, fibrous, white outer coat extending from the cornea to the optic nerve |
| trabecular meshwork | mesh-like structure in the anterior chamber that filters the aqueous humor as it flows into the scleral venous sinus |
| vitreous | jelly-like mass filling the inner chamber between the lens and retina that gives bulk to the eye |
| asthenopia | eyestrain |
| blepharospasm | involuntary contraction of the muscles surrounding the eye causing uncontrolled blinking and lid squeezing |
| exophthalmus/exophthalmos | abnormal protrusion of one or both eyeballs |
| nystagmus | involuntary, rapid, oscillating movement of the eyeball |
| refractive errors | defects in the bending of the light as it enters the eye, causing an improper focus on the retina |
| astigmatism | distorted vision caused by an oblong or cylindrical curvature of the lens or cornea that prevents light rays from coming to a single focus on the retina |
| hyperopia | farsightedness; difficulty seeing close objects when light rays are focused on a point behind the retina |
| myopia | nearsightedness; difficulty seeing distant objects when light rays are focused on a point in front of the retina |
| presbyopia | impaired vision caused by old age or loss of accommodation |
| accomodation | ability of the eye to adjust focus on near objects |
| amblyopia | decreased vision in early life because of a functional defect that can occur as a result of strabismus, refractive errors, or trauma; usually occurs in one eye; also known as lazy eye |
| strabismus / heterotropia/crossed eyes | a condition of eye misalignment caused by intraocular muscle imbalance |
| pterygium | fibrous, wing-shaped growth of conjunctival tissue that extends onto the cornea, developing most commonly from prolonged exposure to ultraviolet light |
| trichiasis | misdirected eyelashes that rub on the conjunctiva or cornea |
| epiphora | abonormal overflow of tears caused by blockage of the lacrimal duct |
| hordeolum / sty | an acute infection of a sebaceous gland of the eyelid |
| tonometry | use of a tonometer to measure intraocular pressure, which is elevated in glaucoma |
| sonography | use of high-frequency sound waves to detect pathology within the eye (foreign bodies and detached retina) |
| slit lamp biomicroscopy | combination of a microscope and a narrow beam of light used to examine the eye, especially the cornea, lens, fluids, and membranes |
| fluorescein angiography | visualization and photography of retinal and intraocular vessels made as florescein dye, which is injected into a vein, circulates through the eye |
| keratoplasty | corneal transplantation; replacement of a diseased or scarred cornea with a healthy one from a matched donor |
| LASIK( Laser- Assisted In Situ Keratomileusis) | a tecnique using the excimer laser to reshape the surface or the cornea to correct refractive error (ex: myopia, hyperopia, and astigmatism) |
| IOL (intraocular lens implant) | implantation of an artificial lens to replace a defective natural lens (ex: after cataract extraction) |
| phacoemulsification | use of ultrasound to shatter and break up a cataract, with aspiration and removal |
| scleral buckling | surgery to treat retinal detachment by placing a band of silicone around the sclera to cinch it toward the middle of the eye and relieve pull on the retina; often combined with other techniques to seal retinal tears (ex: cryoretinopexy) |
| mydriatic | agent that causes dilation of the pupil; used for certain eye examinations |
| miotic | agent that causes the pupil to contract |
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