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Ophthalmic Assisting
Anatomy and Physiology of the Eye
| Term | Definition |
|---|---|
| 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
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