Ophthamology Pathology

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jknell
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207905
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Ophthamology Pathology
Updated:
2013-03-17 22:36:40
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  1. Refractive Errors
    -hyperopia
    -myopia
    -astigmatism
    -accommodation
    -presbyopia
    Impaired vision that improves with glasses

    • Hyperopia:
    • -eye too short for the refractive power of cornea and lens
    • -light focused behind retina
    • -farsighted (difficulty seeing near objects)

    • Myopia:
    • -eye too long for refractive power of cornea and lens
    • -light focused in front of retina
    • -near sighted (difficulty seeing far objects)

    • Astigmatism:
    • -abnormal curvature of cornea
    • -different refractive power at different axes

    • Accommodation:
    • -focusing on near objects → ciliary muscles tighten → zonular fibers relax → lens becomes more convex
    • -occurs with convergence and miosis

    • Presbyopia:
    • -decreased change in focusing ability during accommodation due to sclerosis and decreased elasticity
  2. Glaucoma
    Optic neuropathy, usually with increased IOP

    • 1. Open/Wide angle
    • 2. Closed/narrow angle
  3. Open/wide Angle Glaucoma
    • →-associated with increased age
    • -more common in African Americans
    • -increased risk with FHx
    • -increased risk with increased IOP

    • Presentation:
    • -peripheral then central vision loss
    • -painless (more common in US)

    • Pathophysiology:
    • -primary cause unclear
    • -secondary causes = uveitis, trauma, corticosteroids, vasoproliferative retinopathy
    • -block or decrease outflow at the trabecular meshwork

    • Pathology:
    • -optic disc atrophy
    • -cupping (enlarged cup to disc ratio)
  4. Closed/narrow Angle Glaucoma
    • Pathophysiology:
    • -enlargement or forward movement of lens against central iris leads to obstruction of normal aqueous flow through pupil
    • -fluid builds up behind the iris, pushing peripheral iris against cornea and impeding flow through trabecular meshwork

    • Chronic closure:
    • -often asymptomatic with damage to optic nerve and peripheral vision

    • Acute Closure:
    • -true ophthalmic emergency
    • -increase IOP pushes iris forward causing abrupt angle closure
    • Presentation:
    • -very painful
    • -sudden vision loss
    • -halos around lights
    • -rock-hard eye
    • -frontal HA***DO NOT GIVE EPI B/C OF ITS MYDRIATIC EFFECT
  5. Cataract
    • Risk Factors:
    • -age
    • -smoking
    • -EtOH
    • -excessive sunlight
    • -prolonged corticosteroid use
    • -classic galactosemia
    • -galactokinase deficiency
    • -diabetes (sorbitol)
    • -trauma
    • -infection

    • Presentation:
    • -painless opacification of lens
    • -often bilateral
    • -decrease in vision
  6. Papilledema
    • Pathophysiology:
    • -Optic disc swelling (usually bilateral)
    • -due to increase in intracranial pressure

    • Presentation:
    • -enlarged blind spot
    • -elevated optic disc with blurred margins
  7. CNIII Damage
    • -eye looks down and out
    • -ptosis
    • -pupillary dilation
    • -loss of accomodation
  8. CNIV Damage
    • -eye moves upward
    • -particularly with contralateral gaze and ipsilateral head tilt
    • -problems going down stairs
  9. CNVI Damage
    -medially directed eye that cannot abduct
  10. Marcus Gunn pupil
    • Pathophysiology:
    • -afferent pupillary defect
    • -eg: due to optic nerve damage, retinal detachment

    • Presentation:
    • -decrease bilateral pupillary constriction when light is shone in affected eye relative to unaffected eye
    • -test with "swinging flashlight test"
  11. Retinal Detachment
    • Pathophysiology:
    • -separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, supports retina)
    • -leads to degeneration of photoreceptors and vision loss
    • -may be secondary to retinal breaks, diabetic traction, inflammatory infusions

    • Presentation:
    • -breaks more common in patients with high myopia
    • -often preceded by posterior vitreous detachment (flashes and floaters)
    • -eventual monocular loss of vision ("like a curtain drawn down")

    **Surgical emergency
  12. Age-Related Macular Degeneration
    • Pathophysiology:
    • -degeneration of macula (central area of retina)

    • Presentation:
    • -causes distortion (metamorphopsia) and eventual loss of central vision (scotoma)

    • Dry:
    • -non-exudative
    • ->80%
    • -deposition of yellowish extracellular material beneath retinal pigment epithelium (drusen)
    • -gradual decrease in vision
    • -prevent progression with multivitamin and antioxidant supplements

    • Wet:
    • -exudative
    • -10-15%
    • -rapid loss of vision due to bleeding
    • -secondary to choroidal neovascularization
    • -Tx: anti-VEGF or laser
  13. Visual Field Defects
    • 1. Right anopia → R optic nerve
    • 2. Bitemporal hemianopia → Optic chiasm
    • 3. Left homonymous hemianopia → R optic tract
    • 4. L upper quadrantic anopia → R temporal lesion, MCA)
    • 5. L lower quadrantic anopia → R parietal lesion, MCA)
    • 6. Left Hemianopia with macular sparing → PCA infarct
    • 7. Central scotoma → macular degeneration
  14. Internuclear Ophthalmoplegia (MLF Syndrome)
    • MLF:
    • -pair of tracts that allows for crosstalk between CNVI and CNIII nuclei
    • -coordinates both eyes to move in the same horizontal direction
    • -highly myelinated (must communicate quickly so eyes move at the same time)
    • -lesions seen in patients with demyelination (eg: MS)
    • -when looking left, the left nucleus of CNVI fires which contracts the L LR and stimulates the contralateral (right) nucleus of CN III via the right MLF to contract the R MR

    • Lesion in MLF → Internuclear ophthalmoplegia
    • -lack of communication such that when CN VI nucleus activates ipsilateral lateral rectus, contralateral CN III nucleus does not stimulate medial rectus to fire
    • -abducting eye gets nystagmus (CNVI overfires to stimulate CN III)
    • -convergence normal

    MLF in MS

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