Y1: Term 4: Eyes

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Y1: Term 4: Eyes
2013-02-07 02:49:46

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  1. The Eye

    Sensory organ of vision

    *Conjuctiva thin mucous membrane cover the sclera

    • *Iris function is to vary the opening of its centre
    • *Pupil is determined by parasympathetic and sympathic  chain of autonomic nervous system and controls the amount of light entering the retina 
    • *parasympathetic branch causes constriction of the pupil
    • *sympathetic branch causes dilation of the pupil
  2. Three concentric coats

    • 1. Outer fibrous sclera - tough protective white covering
    • 2. Middle vascular choroid - dark pigmentation to prevent light from reflecting internally and heavily vascularized to deliver blood to retina
    • 3. Inner nervous retina - inner layer retina is the visual layer of the eye light waves are changed into nerve impulses.
  3. The Cornea

    • * the outer layer of the eye which light passes
    • *well supply with nerve endings, made up of mostly  pain fibers - tear occurs during touching & blinking.
    • *vulnerable to damage ( trauma/injury) but have the ability to repair itself.
    • *only transparented tissue in the body
    • *obtain nutrients from the sclera by diffusion from blood vessels.
    • *contribute to refraction or bending of light rays and focussing of vision
    • *avascular but heavily innervated by sensory neurons
  4. Macular degeneration
    • *loss of central vision resulting in blurred vision.
    • *caused by progressive degeneration of the centre of the retina
    • *most common visual impairment and blindness in older adults.
    • * there is no cure.
  5. Glaucoma
    • * a group of conditions causing visual loss due to optic nerve neuropathy
    • *Accompanied by an increase in intraocular pressure
    • *caused by obstruction of the outflow of aqueous humor.
    • *disorder can cause blindness if untreated.
  6. Lens

    • *avascular, transparent biconvex structure 
    • *held in place by zonules attach to surrounding ciliary bodies
    • *contraction and relaxation of muscle fibres of these ciliary bodies allows for near and far vision
  7. Cataracts
    *An opacity of the lens that interferes with transmission of light into the eye onto the retina

    *most common cause of age related visual loss

    *surgicaly corrected by implanting an intraocular lens
  8. Retina
    • *Receives visual images, partially analyses them then sends this modified information to the brain
    • *two layers- outer epithelial layer and inner neural layer-contain millions of photo receptor cells
  9. Visual pathway
    • *Begins with photoceptors cells (light dector) and cones (colour dectector) of the retina.
    • *Their responses are transmitted by bipolar cells to a layer of ganglion cells
    • *The axon of these gaglion cells generate an action potential which is then transmitted via optic nerve to the brain as vision
  10. Developmental considerations
    • *Newborns- eye movement is poorly coordinated, by 3-4 months fixate on single image.
    • *reach adult size by 8 years old.

    • Aging adults: pupil size decreases lens looses elasticity and becomes hard; harder for lens to change shape to accomodate for near vision (>40 years)
    • *Cataract formation (lens opacity), glaucoma and macular deneration.
  11. Subjective data - Health Hx
    • *vision difficulty - which eye or bilateral (both)
    • *Pain
    • *Strabismus, diplopia (cross eye)
    • *Redness/ swelling
    • *watering, discharge
    • *past hx of injury or surgery
    • *family hx of glaucoma
    • *glasses or contact lenses?
  12. Objective data
    • *Snellen eye chart is used to test visual acuity.
    • *Chart 6m from patient
    • *pt covers one eye at a time & read lowest line
    • *top no. represent distance from chart eg 6metre
    • *bottom no. respresents the number next to the smallest line successfully read by pt.
    • *6/6 score indicate perfect vision
    • *the larger the denominator the poorer the visiual acuity
  13. What is a snellen chart?
    chart used to test visual acuity
  14. What's the distance for snellen chart?
  15. Right eye is 6/18, left eye is 6/6 which eye is better?
    Left eye
  16. What is presbyopia
    farsightedness due to weakening of ciliary muscles and loss of elasticity in the lens.
  17. PERRLA
    • Pupil
    • Equal 
    • Round and
    • Reactive to 
    • Light 
    • Accomodation