} The eyes are protected by the skull. } Seven bones form the orbit or eye socket. } Fat in the orbit helps to cushion the globe

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1 } Comparing the eye to a camera Both have lenses for focusing Both have apertures to regulate incoming light pupil Both provide image that is regulated by the brain retina Nicole Patterson, OD, MS, FAAO - Ft. Lauderdale, FL } The eyes are protected by the skull } Seven bones form the orbit or eye socket } The optic foramen is a small opening in the back of the eye that allows the optic nerve to pass through } Fat in the orbit helps to cushion the globe. Yellow - Frontal bone Green - Lacrimal bone Brown - Ethmoid bone Blue - Zygomatic bone Purple - Maxillary bone Aqua - Palatine bone Red - Sphenoid bone } Area in back of eye socket that has no bone } Allows optic nerve to pass back to brain 1

2 } Fat in the orbit helps cushion the globe Orbital Fat } There are six muscles attached to each eye } Each muscle has a unique action } Each muscle is innervated by one of three cranial nerves } The extraocular muscles (EOM s) form a muscle cone Muscle Action MR LR SR Moves eye laterally towards nose Moves eye laterally towards ear Move eye upwards Innerv ation III VI III IR SO IO Moves eye downwards Rotates eye towards nose Rotates eye towards ear III IV III } Lie just under the skin } Circle of muscles } Constrict Close the eye lids Bring the eye brow down Protect the eye ball. } From the outside the eyelids protect the globe } Blink reflex protects the eyes } Blinking helps with lubrication } Tears flush bacteria and foreign matter out of the eye 2

3 5/14/15 The eyelids are covered by skin (epidermis) on the outside The eyelids are lined on the inside with palpebral conjunctiva Palpebral conj. Has glands that secrete oils and mucous to lubricate the eye Along eyelid margins are tiny glands called meibomian glands They secrete oils for lubrication Canthus The corner of each eyelid Later canthus is towards ear Medial canthus is towards nose The palpebral conj. Is continuous with the white part of the eye (bulbar conjunctiva) This prevents anything from getting behind the eye Eyelid margins have follicles that lashes grow from Medial canthus contains mound of flesh called caruncle 3

4 } Puncta Openings on medial side of upper and lower lid Allow for tear drainage } Reflex tears (FB and bright light) and emotional tears come from the lacrimal gland } Kraus and Wolfring also contribute to the aqueous layer } The white part of the eye } Tough fibrous part of the eye that helps it eye maintain its shape } The muscles that move the eye attach to the sclera via tendons } Overlies the episclera } Clear covering over the colored part of the eye } There are no blood vessels in a healthy cornea } The cornea meets the conjunctiva at the limbus 4

5 } The cornea is a curved surface } It refracts (bends) the light entering the eye } Consists of five layers Epithelium is the outermost layer Regenerates very quickly (within 24 hours) Bowman s layer Stromal layer Descemet s layer Endothelium } Inner most layer of the cornea } Does not regenerate } If cells are lost or damaged the remaining cells spread out to cover the loss } Endothelium can become cloudy resulting in decreased vision } Provides about 40 D of power for the eye } Between the endothelium and the iris is a chamber containing fluid } Fluid is aqueous humor and contains fluid similar to blood plasma in composition } Angle of the eye Area where cornea and sclera meet } The angle of the eye is made up of a meshwork that drains the aqueous humor from the eye } The trabeculum leads to the canal of Schlemm which leads to capillaries } When there is a blockage pressure builds up in the anterior chamber and can cause glaucoma 5

6 5/14/15 The iris is the partition between the anterior and posterior chamber Two muscles Dilator Located at the base of the iris Continually produces aqueous humor Ciliary body is continuous with the ciliary muscles which Aqueous humor drains out trabeculum, canal of Schlem, capillaries control the shape and focus of the eye Opens the iris Sphincter Closes the iris These to muscles can give indication as to overall health of individuals The crystalline lens is composed of aqueous humor As a person ages the crystalline changes composition and begins to cloud As the lens clouds cataracts form Provides about 20 D of power for the eye Most problems causing vision loss are located in the posterior segment Lens Connect the lens to the ciliary body Center the lens in the eye As the ciliary body contracts the zonules pull on the lens changing the shape As the shape of the lens changes the focusing of the eye also changes 6

7 } Behind the lens eye is filled will jelly-like substance called vitreous humor } Remember aqueous was constantly being formed, but vitreous is stable } With age vitreous can clump together and form floaters } Large floater common 60s to 80s happens with the vitreous pulls away from back of eye This is NOT as serious as retinal detachment and happens in most individuals } A fundus view aka posterior pole } The inner surface of the posterior segment is covered by the retina Atlas of Human Anatmony F. Netter

8 } Layer of vessels underneath the retina that provide nourishment } The choroid lies beneath the sclera } Contains superficial blood vessels and deeper capillaries. } A thin layer separates the choroid from the retina. } Disease can compromise integrity of the membrane, allowing fluid to accumulate under retina } Center of retina } High concentration of cones } Responsible for fine vision } Susceptible to damage from diseases Macular degeneration retina.html 8

9 } The central pit in the macula that produces the sharpest vision } Has a very high number of cones and no retinal blood vessels } FAZ (foveal avascular zone) The central.5mm of the retina around the foveal pit where there are no blood vessels specialties/macular_degeneration information_overview_anatomy.ht ml 9

10 } Sends the signal from the eye to the brain } Is an extension of the brain } Composed of nerve fibers } Contains a cup that can become enlarged in disease } Like other nerves in the body, once damaged there is no way to repair } Nerve fibers may die causing the nerve to become pale } The optic nerve enters the eye through a sieve like structure in the sclera know as the lamina cribosa. } Optic nerve has a sheath around it which contains blood vessels } Forms the blind spot in vision } Nerve head is referred to as disc and is used as landmark 3 DD from macula 10

11 } Appear like tree branches sprouting out through the nerve } Vessels stop short of the macula 11