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Ocular Anatomy

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.

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Ocular Anatomy

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  1. Ocular Anatomy A Vision Teacher ‘s Guide

  2. The Human Eye

  3. Eyelid • In addition to tear spreading, the eyelid is primarily responsible for corneal nutrition • Also provides protection to cornea • Lashes offer additional protection

  4. 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

  5. Lacrimal System

  6. 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

  7. 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

  8. 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)

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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

  14. Zonules • Attach the lens to the ciliary body • May become broken or stretched causing the lens to move out-of-place

  15. 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

  16. Choroid • A brown vascular sheet lying between the sclera and the retina • This is the blood supply for the retina

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

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