15. EYE

Accommodation: Normal adjustment of the eye to focus on objects from far to

near. The ciliary body adjusted the lens and the pupil constricts. When the eye

disaccomodates, it focuses from near to far. The ciliary body flattens the lens and the

pupil dilates.

Anterior chamber: Area behind the cornea and in front of the lens and iris. It

contains aqueous humor.

Aqueous humor: Fluid produced by the ciliary body and found in the anterior

chamber. A humor is any body fluid, including blood and lymph.

Biconvex: Having two sides that are rounded, elevated, and curved evenly, like part

of a sphere. The lens of the eye is a biconvex body.

Choroid: Middle, vascular layer of the eye, between the retina and the sclera.

Ciliary body: Structure on each side of the lens that connects the choroid and iris. It

contains ciliary muscles, which control the shape of the lens, and it secretes aqueous

humor.

Cone: Photoreceptor cell in the retina that transforms light energy into a nerve

impulse. Cones are responsible for color and central vision.

Conjunctiva: Delicate membrane lining the eyelids and covering the anterior

eyeball.

Cornea: Fibrous transparent layer of clear tissue that extends over the anterior

portion of the eyeball.

Fovea centralis: Tiny pit or depression in the retina that is the region of clearest

vision.

Fundus of the eye: Posterior, inner part of the eye.

Iris: Colored pigmented membrane surrounding the pupil of the eye.

Lens: Transparent, biconvex body behind the pupil of the eye. It bends light rays to

bring them into focus on the retina.

Macula: Yellowish region on the retina lateral to and slightly below the optic disc;

contains the fovea centralis, which is the area of clearest vision.

Optic chiasm: Point at which optic nerve fibers cross in the brain.

Optic disc: Region at the back of the eye where the optic nerve meets the retina. It

is the blind spot of the eye because it contains only nerve fibers, no rods or cones,

and is thus insensitive to light.

Optic nerve: Cranial nerve carrying impulses from the retina to the brain.

Pupil: Dark opening of the eye, surrounded by the iris, through which light rays

pass.

Refraction: Bending of light rays by the cornea, lens and fluids of the eye to bring

the rays into focus on the retina.

Retina: Light-sensitive nerve cell layer of the eye containing photoreceptor cells.

Rod: Photoreceptor cell of the retina essential for vision in dim light and for

peripheral vision.

Sclera: Tough, white outer coat of the eyeball.

Thalamus: Relay center of the brain. Optic nerve fibers pass through the thalamus

on their way to the cerebral cortex.

Vitreous humor: Soft, jelly-like material behind the lens in the vitreous chamber;

helps maintain the shape of the eyeball.

Iridectomy: A portion of the iris is removed to improve drainage of aqueous humor

or to extract a foreign body.

Ophthalmologist: A medical doctor who specializes in treating disorder of the eye.

Optometrist: Nonmedical professional who can examine eyes to determine vision

problems and prescribe lenses.

Optician: Nonmedical professional who grinds lenses and fits glasses but cannot

prescribe lenses.

Phacoemulsification: Technique of cataract extraction using ultrasonic vibrations

to fragment the lens and aspirate it from the eye.

Amblyopia: Amblyopia is partial loss of sight and is also known as lazy eye because

it is associated with failure of the eyes to work together to focus on the same point.

Nyctalopia: Night blindness is poor vision at night, but good vision on bright days.

Deficiency of vitamin A leads to Nyctalopia.

Photophobia: Sensitivity to light.

Scotoma: An area of depressed vision surrounded by an area of normal vision; a

blind spot. This can result from damage to the retina or the optic nerve.

Esotropia: Inward turning of the eye.

Exotropia: Outward turning of the eye.

Strabismus: Defect in eye muscles so that both eyes cannot be focused on the

same point at the same time.

Astigmatism: Defective curvature of the cornea or lens of the eye.

Hyperopia: Farsightedness.

Myopia: Nearsightedness.

Presbyopia: Impairment of vision as a result of old age.

Cataract: Clouding of the lens, causing decreased vision.

Chalazion: Small, hard, cystic mass on the eyelid; formed as a result of chronic

inflammation of a sebaceous gland along the margin of the eyelid.

Diabetic retinopathy: Retinal effects of diabetes mellitus include microaneurysms,

hemorrhages, dilation of retinal veins, and neovascularization.

Glaucoma: Increased intraocular pressure results in damage to the retina and optic

nerve with loss of vision.

Hordeolum: Localized, purulent, inflammatory staphylococcal infection of a

sebaceous gland in the eyelid.

Blepharitis: Inflammation of eyelid, causing redness, crusting and swelling along lid

margins.

Dacryocystitis: Blockage, inflammation, and infection of a nasolacrimal duct and

lacrimal sac, causing redness and swelling of lower lid.

Ectropion: Outward sagging and eversion of the eyelid, leading to improper

lacrimation and corneal drying and ulceration.

Entropion: Inversion of the eyelid, causing the lashes to rub against the eye;

corneal abrasion may result.

Ptosis: Drooping of upper lid margin as a result of neuromuscular problems.

Xanthelasma: Raised yellowish plaque on eyelid caused by lipid disorder.

Macular degeneration: Progressive damage to the macula of the retina.

Nystagmus: Repetitive rhythmic movements of one or both eyes.

Retinal detachment: Two layers of the retina separate from each other.

Hypertropia: Upward deviation of one eye.

Hypotropia: Downward deviation of one eye.

Diplopia: Double vision.

Fluorescein angiography: Intravenous injection of Fluorescein (a dye) followed by

serial photographs of the retina through dilated pupils.

Ophthalmoscopy: Visual examination of the interior of the eye.

Slit lamp microscopy: Examination of anterior ocular structures under microscopic

magnification.

Visual acuity test: Clarity of vision is assessed. A patient reads from a snellen chart

at 20 feet.

Visual field test: Measures the area within which objects are seen when the eyes

are fixed, looking straight ahead without movement of the head.

Enucleation: Removal of the entire eyeball.

Keratoplasty: Surgical repair of the cornea.

Laser photocoagulation: Intense, precisely focused light beam creates an

inflammatory reaction that seals retinal tears and leaky retinal blood vessels.

LASIK: Use of an excimer laser to correct errors of refraction (myopia, Hyperopia,

and astigmatism).

Scleral buckle: Suture of a silicone band to the sclera over a detached portion of

the retina.

Vitrectomy: Removal of the vitreous humor.