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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
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Glaucoma
Optic neuropathy, usually with increased IOP
- 1. Open/Wide angle
- 2. Closed/narrow angle
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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)
 
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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
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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
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Papilledema
- Pathophysiology:
- -Optic disc swelling (usually bilateral)
- -due to increase in intracranial pressure
- Presentation:
- -enlarged blind spot
- -elevated optic disc with blurred margins
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CNIII Damage
- -eye looks down and out
- -ptosis
- -pupillary dilation
- -loss of accomodation
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CNIV Damage
- -eye moves upward
- -particularly with contralateral gaze and ipsilateral head tilt
- -problems going down stairs
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CNVI Damage
-medially directed eye that cannot abduct
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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"
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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
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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
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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
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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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