eye review Flashcards
what are the refractive errors and how to we treat them
impaired vision that be fixed with corrective lens.
hyperopia
eye too short for the refractive power of the cornea and lens. light focused behind the retina.
myopia
eye too long for the refractive power of the cornea and lens. light focused in front of the retina.
astigmatism
abnormal curvature of the cornea resulting in different refractory indexes at different axes. \
accommodation
focusing on nearby objects. colliery muscle tightens. zonular fibers relax and the lens becomes more convex. occurs with convergence and mitosis.
presbyopia
decreased change in the focusing ability during accommodation due to sclerosis and decreased elasticity. this happens with aging.
Uvietis
inflammation of the Uveal coat and is often associated with systemic inflammatory disorders. sarcoid, rheumatoid, juvenile idiopathic arthritis, TB, HLA-B27 associated conditions.
retinitis
retinal edema and necrosis leading to scar. often associated with viruses like HSV, CMV, HZV.
open/wide angle glaucoma
characterized by peripheral then central vision loss usually with increased IOP; optic disc atrophy with cupping.
what is open/wide angle glaucoma associated with?
older age, African American, family history, increased intraociular pressure.
what the primary and secondary causes of open/wide angle glaucoma
primary = unsure.
secondary: Uveitis, trauma, corticosteroids, vasoproliferative retinopathy that can block the outflow at the trabecular meshwork.
closed/narrow angle gluacoma
enlargement or forward movement of lens against the central iris leads to obstruction of the normal aqueous flow through pupil. fluid builds up behind the iris. this pushes the peripheral iris toward the cornea and this impedes the flow of aqueous through the trabecular meshwork. this is often asymptomatic
acute closure of the angle
pain! emergency. sudden vision loss, halos around lights, rock hard eye, frontal headache.
what do you not give in acute angle glaucoma
epinephrine –mydriatic effect.
what are the risk factors for cataracts
smoking, age, EtOH, excessive sunlight, corticosteroids, trauma, infection, diabetes (sorbitol), classic galatosemia, galactokinase deficiency.
what does CN VI innervate
lateral rectus.
what does CN IV innervate
superior oblique
what does CN III innervate
innervates the rest of the oculomotor units
what happens with CN III damage
down and out eye. ptosis, pupillary dilation, loss of accommodation
what happens with CN IV damage
eyes move upward, particularly with contralateral gaze and ipsilateral head tilt (problems going down stairs).
what happens with CN VI damage
medially directed eye that cannot abduct.
what causes miosis of the pupil
constriction of the pupil is caused by parasympathetics. 1) edinger-westfall nucleus (CN III), to ciliary ganglion
2) short colliery nerves to pupillary sphincter muscles.
what causes mydriasis
dilation is caused by sympathetics. 1) hypothalamus to ciliospinal center of budge (C8-T12). 2) exit at T1 to superior cervical ganglion, which travels along the cervical sympathetic chain near the lung apex and subclavian vessels. 3) plexus along the internal carotid, through the cavernous sinus; enters the orbit as long cilliary nerve to pupillary dilator muscles.
How the pupillary light reflex works
light enters the retina sends signals via CN II to pretectal nuclei in midbrain that activates bilateral Edinger-Westfall nuclei and the pupils contract bilaterally.
Marcus-Gunn pupil
afferent pupillary defect due to optic nerve defect of detached retina. there is decreased bilateral pupillary constriction when light is shone in affected eye relative to the unaffected eye.
what are the signs of motor deficit in CN III. common causes
ptosis and down and out gaze.
mainly affected by vascular disease, such as diabetes
what is the medial longitudinal fasciculus and what does it do
the MLF is a pair of tracts that allows for crosstalk between CN VI and CNIII nuclei. it coordinates both eyes to move in horizontal direction.
why and how is MLF associated with multiple sclerosis
the MLF is highly myelinated and is affected in MS. one of the features of MS if internuclear ophthalmoplegia.
is convergence affected in demyelinating syndromes that affect the MLF?
No. convergence is usually preserved.
internuclear ophthalmoplegia
it is a disorder of lateral gaze in which the affected eye has a defect in adduction. when this happens the unaffected eye is looking outward and has lateral nystagmus.
If there is a right sided INO, then when looking left and when the left eye abducts it will have nystagmus. the right eye will not move from midline.
