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Ophthalmic Assisting

Anatomy and Physiology of the Eye

Globe Eyeball
Cornea Clear, round membrane at the front of the globe.
Iris Colored circle of tissue behind the cornea which controls the amount of light entering the eye.
Pupil Opening in the center of the iris that reduces and enlarges to allow light to enter the eye.
Crystalline Lens Second part of the optical focusing system located immediately behind the iris.
Vitreous Clear, jelly-like substancewhich fills the large space behind the crystalline lens.
Retina Transparent layer of tissue that forms the innermost lining of the globe.
Optic Nerve Carries electrical impulses to the brain which are then integrated in the brain's visual cortex to produce the sensation of sight.
Axial Length Length of the eye from front to back.
Pachymetry An ultrasound test which measures the thickness of the cornea.
Adnexa The tissues and structures surrounding the eye.
Orbit Pear-shaped, bony cavity in the skull made up of 7 bones that house the globe, extraocular muscles, blood vessels , and the nerves, all of which are cushioned by layers of fat.
Blowout Fracture A fracture in the floor of the orbit that results from blunt force trauma.
Extraocular Muscles The muscles that control movement of the globe.
Medial Rectus Muscle Rotates the eye inward towards the nose (ADDUCTION)
Lateral Rectus Muscle Rotates the eye outward toward the temple (ABDUCTION)
Superior Oblique Muscle Primarily causes a torsional (twisting and turning) movement and twists the eye down and inward (INCYCLOTORSION)
Inferior Oblique Muscle Primarily causes a torsional (twisting and turning) movement and twists the eye up and outward (EXCYCLOTORSION)
Binocular Vision When the eyes are directed toward a single target and are perfectly aligned.
Fusion When the brain blends the seperate images received by the two eyes so that the person perceives a single view.
Strabismus Condition resulting when the extraocular muscles do not work in a coordinated manner and the eyes become misaligned and the vision may be disturbed.
Eyelids Complex moveable cover of the outer portion of the eyeball. Consists of upper and lower component of skin, tarsus, delicate muscles, eyelashes, glands, and conjunctiva.
Palpebral Fissure Almond-shaped opening between the upper and lower lids.
Medial Canthus Point where the lids meet on the inner (nasal) side of the palpebral fissure.
Lateral Canthus Temporal(outer) junction of the lids.
Anterior Front
Cilia (Eyelashes) Protects the surface of the eye by sweeping away airborne dust particles and other foreign matter when the eyelids blink.
Trichiasis A condition when an eyelash grows in the wrong direction and rubs the surface of the eye causing irritation to the cornea.
External Hordeolum (Stye) A reddened sore lump on the outer edge of the lid caused when a lash follicle becomes inflamed.
Posterior Back
Meibomian Glands Oil-secreting glands hidden in the tissue of the eyelids, located on the posterior margin of the eyelid closest to the globe.
Internal Hordeolum Swelling on the inner eyelid caused when a meibomian gland becomes inflamed or infected.
Chalazion Lump on the outer lid caused by prolonged inflammation of the meibomian glands.
Blepharitis Inflammatory condition that produces reddened and crusted lid margins.
Tarsus (Tarsal Plate) Dense, plate-like framework in the middle layer of the upper and lower eyelid which gives the eyelids their firmness and shape.
Orbicularis Oculi Circular muscle in the middle layer of the eyelid that closes the eye when it contracts, as in winking.
Levator Palpebrae Superioris Muscle in the middle layer of the eyelid that is attached to the upper tarsal plate; raises the upper lid when it contracts.
Ptosis A condition when the upper lid droops down and can not lift fully caused when the levator muscle loses its ability to lift the eyelid to its full extent.
Ectropion A condition when there is malformation or damage to the eyelid tissues that causes the lower lid margin to fall or pull away from the eye.
Entropion A condition when there is malformation or damage to the eyelid tissues that causes the lower lid margin to be turned inward.
Conjunctiva Third layer of the eyelids; thin, tranlucent mucous membrane that lines the inner surface of the lid and the outer front surface of the eyeball, except for the cornea.
Palpebral Conjunctiva Portion of conjuntiva lining the eyelids.
Bulbar Conjunctiva Section of conjunctiva that covers the outer eyeball.
Fornix (Cul-de-Sac) Loose packet of conjunctival tissue located beneath the upper and lower lids where the palpebral and bulbar conjunctiva meet.
Conjunctivitis A condition where irritation, allergy, or infection cause the small conjunctival blood vessels to swell and the conjunctiva to appear red.
Subconjunctival Hemorrhage (SCH) A condition caused when a conjunctival blood vessel ruptures, thus allowing blood to flow under the tissue.
Lacrimal Apparatus Consists of the orbital structures that produce tears.and the ducts that drain the excess fluid from the front of the eye into the nose.
Tear Film A 3-layered coating that covers the front surface of the globe.
Lacrimal Gland Produces moisture, oxygen, and nutrients to nourish the cornea.
Mucinous Sticky
Goblet Cells Produce a mucinous fluid in the innermost layer of the tear film.
Foreign-Body Sensation (FBS) Feeling of irritation and grittiness in the eye.
Punctum (Upper/Lower) Located on the upper and lower lid margins near the nose, tiny openings that tears pass through; entrance to the canaliculi.
Canaliculus (Upper/Lower) Tubes that carry tears to the lacrimal sac.
Lacrimal Sac Dilated end of the lacrimal duct that fill with tears carried by the canaliculi.
Nasolacrimal Duct Carries tears from the lacrimal sac to the nasal cavity.
Dacryocystitis Inflammation of the lacrimal sac
Anterior Segment Front of the eye which includes the structures between the front surface of the cornea and the vitreous.
Posterior Segment Composed of the vitreous and the retina.
Corneal Epithelium The cornea's first line of defense against infection and injury.
Bowman's Membrane Acts as an anchor for the epithelial layer.
Corneal Stroma Main body of the cornea.
Descemet's Membrane Contributes rigidity to the cornea.
Corneal Endothelium Serve as pumps to maintain a proper fluid balance with the cornea.
Corneal Abrasion Scratch on the corneal epithelium.
Corneal Ulcer Results if an injury to the corneal epithelium becomes infected.
Sclera The white tissue surrounding the cornea.
Limbus Junction between the sclera and the cornea, also the point where the bulbar conjunctiva terminates since it does not cover the cornea.
Anterior Chamber Small compartment between the cornea and iris that is filled with clear, transparent fluid.
Aqueous Humor Clear, transparent fluid that fills the anterior chamber and is produced by secretory tissue located behind the iris.
Anterior Chamber Angle (Filtration Angle) Junction of the cornea and iris in which aqueous fluid leaves the eye.
Trabecular Meshwork A spongy structure that filters the aqueous fluid and controls its rate of flow out of the eye.
Canal of Schlemm Conduit in the sclera in which aqueous humor dains.
Aqueous Veins Collector channels which carry aqueous fluid from the canal of Schlemm to the venous vessels on the conjunctiva.
Uvea (Uveal Tract) Main vascular compartment of the eye responsible for providing most of the blood supply and much of the nourishment for the eye.
Dilator Muscle Stretches from the pupils to the boundaries of the iris; contract to widen (dilate) the pupil in reduced lighting conditions.
Sphincter Muscle Encircles the pupil and contracts to make the pupil smaller in response to bright light.
Posterior Chamber Space between the back of the iris and the front of the vitreous that is filled with a clear, transparent fluid.
Ciliary Body Band-like structure made up of muscle and secretory tissue that extends from the edge of the iris and encircles the inside of the sclera toward the front of the eye.
Ciliary Processes A series of folds, rows, or ridges in the inner surface of the ciliary body that secrete the aqueous humor that fills the anterior and posterior chambers.
Ciliary Muscle Muscle fibers in the ciliary body.
Choroid A layer of tissue that lies between the sclera and retina; the innermost surface of the posterior segment, made up mostly of blood vessels which supply nourishing blood to the outer layers of the retina.
Zonules Transparent fibers that suspend the lens; radiates from the lens and attaches to the ciliary body.
Cortex Clear, paste-like protien that surrounds the nucleous (core) of the inner lens.
Accomodation When the curvature of the lens changes in order to focus images of objects that are closer to the eye.
Presbyopia A condition when a significant amount of the lens' ability to increase its curvature is lost and an individual can longer focus on very near objects.
Opacification Clouding
Cataract Clouding of the lens.
Floaters Small clumps or strands of concentrated gel floating in the vitreous which cast shadows on the retina and appear to the patient as moving spots.
Pigment Epithelium Pigmented layer of the retina.
Photoreceptor Light-sensitive
Rods Largly responsible for vision in reduced light (night vision) and for peripheral (side) vision.
Cones Provide sharp central vision and the perception of color.
Optic Nerve Head (Optic Disc) Located in the retina where the central retinal artery enters and the central retinal vein exits.
Macula Oval-shaped, highly pigmented yellow spot near the center of the retina.
Fovea Center of the macula; the largest concentration of cone cells.
Created by: dmontemurro