Ocular Anatomy


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Ocular Anatomy

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