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Ocular Anatomy
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Ocular Anatomy

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    Ocular Anatomy Ocular Anatomy Presentation Transcript

    • Ocular Anatomy A Vision Teacher ‘s Guide
    • The Human Eye
    • Eyelid
      • In addition to tear spreading, the eyelid is primarily responsible for corneal nutrition
      • Also provides protection to cornea
      • Lashes offer additional protection
    •  
    • Lacrimal System/Tear Film
      • Lacrimal system is responsible for tear production and drainage
      • Made up of 3 layers
      • Created primarily by lacrimal apparatus and meibomian glands
      • Lubricate the eyeball, provides oxygen/nutrition for cornea, has antibacterial properties and helps wash away debris
      • Also have unique composition which keeps surface of cornea slick
    • Lacrimal System
    • Cornea
      • Made up of 5 layers
      • Specialized Transparent Tissue
        • No blood vessels
      • Primarily responsible for refracting light
        • Does more of the job than the lens
      • More nerve endings than anywhere else in the body
        • Protection to the eye
      • The only part of the eye that is transplanted from one person to another
    •  
    • Aqueous humor
      • Fills space between cornea and iris
      • Continuously produced by ciliary body
      • Flows into chamber through the pupil
      • Drains from eye through trabecular meshwork to canal of schlemm
      • Nourishes the cornea and lens
      • Gives front of eyeball form and shape
        • Anterior chamber is area between the cornea and the iris: filled with aqueous
        • Posterior chamber is the area behind the iris and in front of the lens: filled with aqueous
    •  
    • Limbus
      • Juncture between the cornea and the sclera
      • Nourishes peripheral cornea…assists in corneal wound healing
      • Pathway for aqueous outflow (contains trabecular meshwork and canal of schlemm)
    •  
    • Conjunctiva
      • Thin translucent mucous membrane starts at the limbus and covers the sclera and inner surface of the eyelid
      • Has some responsibility of tear production
      • Subject to infection…problems from contact lens use
      • Can be degraded by environmental conditions heat, wind, dust, etc.
    •  
    • Sclera
      • Whites of the eye
      • Made up of 3 layers
      • Tough, fibrous tissue: site of extra-ocular muscle attachment
      • Opaque...allows no light to enter
      • Subject to inflammation
    •  
    • Iris
      • The colored part of the eye…unique to every individual like a fingerprint
        • Color is dependent on the amount of pigment
      • A diaphragm, the iris has tiny muscles that control the light levels in the eye
      • Has 2 layers
      • Pupil is located in the center of the iris
        • pupil = hole: it is not an eye structure per se
    •  
    • Lens
      • Transparent, biconvex structure, held in place by ciliary zonules
      • Composed of 6 layers
      • Refracts light
      • Nutrition comes from aqueous humor…insoluble deposits of proteins build up over time = cataracts
        • A clouding of the lens and capsule
      • Live long enough and you WILL have some degree of cataract
      • cataracts also caused by other agents
    •  
    • Ciliary body
      • Connects the choroid with the iris
      • Has three parts including:
        • The ciliary muscle is ring shaped muscle that controls the shape of the lens (accommodation)
        • The ciliary process is the attachment site for the zonules and produces the aqueous in the pars plicata
        • The ciliary ring is attached to the choroid and is composed of the pars plana. The pars plana has no known function in the post-fetal eye thus this is a safe area through which surgical instruments may be inserted
    •  
    • Zonules
      • Attach the lens to the ciliary body
      • May become broken or stretched causing the lens to move out-of-place
    •  
    • Vitreous
      • A thick, transparent gel like substance that fills the center of the eyeball, giving it form and shape
      • A canal runs through the vitreous from optic disk to the lens. It is a developmental leftover from the hyaloid artery. Usually regresses but may persist and result in floaters
      • May see reference to hyaloid membrane. This transparent tissue surrounds the vitreous and separates it from the retina
      • Central retinal veins and arteries extend in bundles, exit and enter respectively through the optic nerve
    •  
    • Choroid
      • A brown vascular sheet lying between the sclera and the retina
      • This is the blood supply for the retina
    •  
    • Retina
      • Most internal layer of eye, facing the vitreous
      • Converts light energy into electrical energy which is then sent to the brain via the optic nerve
      • Actually an extension of brain tissue
      • Composed of 10 layers…contains photoreceptors: cones, near center (responsible for seeing detail and color) and rods, in periphery (responsible for seeing in low light and seeing movement)
      • Point of sharpest vision is in the fovea; located in the center of the macula
    •  
    • Ora Serrata
      • A serrated juncture between the retina and ciliary body marking the transition between non-sensitive tissue and the retinal portion with many layers and specialized photoreceptor cells
    •  
    • Intra-ocular muscles
      • Purpose is to move eyes
      • Maintain binocularity
      • 6 muscles
        • medial rectus (MR) —moves the eye toward the nose
        • lateral rectus (LR) —moves the eye away from the nose
        • superior rectus (SR) —primarily moves the eye upward and secondarily rotates the top of the eye toward the nose
        • inferior rectus (IR) —primarily moves the eye downward and secondarily rotates the top of the eye away from the nose
        • superior oblique (SO) —primarily rotates the top of the eye toward the nose and secondarily moves the eye downward
        • inferior oblique (IO) —primarily rotates the top of the eye away from the nose and secondarily moves the eye upward
    •  
    • Optic Nerve
      • Purpose is for energy transmission to brain
      • Subject to underdevelopment, damage, inflammation
      • Contains over 1 million nerve fibers…once severed cannot be reconnected=no “eye transplant”
      • Upon examination only the head can be seen by doctor. Should appear as yellowish pink, flat and with distinct margins
      • The cup to disk ratio is evaluation as a measure of health…increase in size of cup may indicate elevated pressure
    •  
    • Optic Nerve Pathways/Visual Cortex
      • Message is carried down the optic nerve through pathways to occipital cortex; here vision becomes sight
      • At the optic chiasm, the nasal nerve fibers cross; temporal nerve fibers go straight back to cortex; this arrangement impacts on visual fields
      • Results in visual field losses can be predicted based on where damage is located on the optic nerve
      • When damage is located anterior of the optic chiasm; it is likely there will be a cortical component to the field loss
    •  
    •