Eyes

Question 0

Myopia

Answer 0

Near sightedness, where the image forms before the retina because the eyeball is too long or the refractory power is too high

Question 1

Emmetropia

Answer 1

Correct eyeball size and refractory power such that the image forms appropriately on the retina

Question 2

Hyperopia

Answer 2

far-sightedness, where the image forms past the retina because the length of the eye is too short or the refractory power is weak

Question 3

Cornea (content and function)

Answer 3

Avascular w/ highly ordered collagen –> transparent.
* thickness varies across –> best vision @ central, where thinnest.
F(x): main focusing mech. (2/3 of total (60 diopter) converging power); also protective w/ selective permeability.

Question 4

Corneal layers (3)

Answer 4

1. endothelium
2. stroma
3. epithelium **innervated w/ sensory afferents –> corneal scratch hurts!

Question 5

Bowman’s Layer

Answer 5

very thin, acellular layer just below the corneal epithelium;
(part of cornea).
* does NOT regernerate, so injury => corneal opacity (vision deficit)

Question 6

corneal stroma

Answer 6

thickest layer of cornea, contains highly ordered collagen type I
(uniform spacing and thickness).
** collagen & proteoglycan IS regrown after injury, but less orderly => opaque scar & vision deficit.

Question 7

Corneal endothelium

Answer 7

innermost layer of cornea, transports Na, K, & H ions + removes water from stroma (“deturgescence”) –> to maintain clarity of vision.

• • limited regeneration w/ injury.
• ** water removal decreases w/ age –> increased cloudiness.

Question 8

sclera

Answer 8

most (80%) of eye surface; ~avascular, made of less organized collagen + higher water content than cornea (–> not clear).
w/ sensory & autonomic innervation, extraocular m insertions, & holes for optic nerve, etc.
** slow to heal, but will w/o affecting vision.

Question 9

anterior & posterior chambers

Answer 9

Both filled w/ aqueous humor to provide O2 & nutrients to cornea, lens, & trabecular meshwork.
Anterior: btwn cornea & iris/lens
Posterior: btwn iris & vitreous chamber

Question 10

Aqueous humor (flow, content, etc)

Answer 10

Made by ciliary body, flows into anterior chamber, then drains via Schlemm’s canal (trabecular meshwork – main resistance to flow).

• maintains clarity bc NO plasma cells or proteins.
• ** if builds up –> glaucoma! (high intraocular pressure)

Question 11

3 responsibilities of Ciliary Body

Answer 11

1. produce aqueous humor
2. regulate aqueous humor outflow
3. accommodation (adjust vision using ciliary muscles)

Question 12

Trabecular meshwork

Answer 12

thin channels of connective tissue, lined w/ epithelium & gap junctions;
= main source of resistance to aqueous humor outflow/drainage.

Question 13

path of aqueous humor flow

Answer 13

1. ciliary body (produced) –> anterior chamber
2. –> Schlemm’s canals (trabecular meshwork)
3. –> collector canals
4. –> episcleral veins

Question 14

Glaucoma

Answer 14

painless, often unnoticed/”symptomless” disease resulting in blindness.
due to increased intraocular pressures (from reduced aqueous humor outflow) +/- other unknown mechs.

Question 15

Uvea (contents, function)

Answer 15

Uvea = iris, ciliary body & choroid;
= highly vascular, pigmented cells.
F(x): provide nutrients to lens, cornea & trabecular meshwork

Question 16

Iris

Answer 16

highly vascular colored segment around pupil, contains:

• iris sphincter muscle: circular fibers, w/ parasymp. innervation.
• iris dilator muscle: radial fibers, w/ sympathetic innervation.
• help w/ visual accomodation

Question 17

Ciliary muscle

Answer 17

contracts w/ parasympathetic stimulation, ==> lens thickens (for visual accomodation) by releasing pressure.

Question 18

Presbyopia

Answer 18

loss of visual acuity w/ age due to decreased elasticity of the lens

Question 19

Lens

Answer 19

Asymmetric, biconcave, avascular & NOT innervated;
Mostly water w/ some protein (crystallin).
– adjusts thickness in order to keep light focused on retina for any object distance.

Question 20

Cataracts

Answer 20

protein aggregations that decrease visual acuity, caused by conversion of a-crystallin to albuminoid in aging lens.
* preventable & treatable!*

Question 21

Vitreous body

Answer 21

clear substance filling most of eye past lens,
– 99% water + hyaluronic acid-collagen gel.
lets light pass through eye to retina.
** attached everywhere except anteriorly –> posterior detachment appears like retinal detachment! **

Question 22

macula & fovea

Answer 22

Macula = central region of retina, w/ high clarity.
Fovea = center of macula, w/ highest density of cones & no blood vessels.
* macular degeneration happens w/ age, not preventable. :(

Question 23

Oculomotor nerve f(x)

Answer 23

Motor: to levator m. + all Extraocular mm except superior oblique and lateral rectus mm.
Parasympathetic: to ciliary body & iris sphincter m.

Question 24

Arteritic Ischemic Neuropathy (Temporal Arteritis)

Answer 24

Sx: monocular decreased vision, temporal pain & scalp sensitivity, jaw claudication, fatigue, Aff. pupillary defect; *age > 60 Tx: Emergency! High dose steroids, biopsy

Question 25

Non-Arteritic Ischemic Optic Neuropathy

Answer 25

= microvascular insult to optic n., Risk factors: HTN, diabetes Sx: sudden decrease in vision, aff. pupillary defect Tx: none, assess for risk of temporal arteritis

Question 26

Central Retinal Artery Occlusion

Answer 26

Sx: very acute monocular vision loss (= embolic occlusion of retinal a.) Dx: pale retina w/ "cherry red spot," *rule out temporal arteritis Tx: if <2 hrs reduce eye P, occular massage, etc. (to improve occular circulation)

Question 27

Central Retinal Vein Occlusion

Answer 27

= obstruction of venous outflow Risk factors: HTN, DM, glaucoma, hypercoagulability Dx: "Blood & Thunder" retina, decreased vision Tx: laser or injections to prevent neovascularization

Question 28

Vitreous Hemorrhage

Answer 28

= blood in vitreous cavity Causes: diabetes, trauma, retinal tear Tx: observe, laser surgery if diabetic

Question 29

Ruptured Globe (trauma)

Answer 29

Sx; Subconjunctival hemorrhage, hyphema, peaked pupil | Tx: eye shield, systemic antibiotics, CT to rule out foreign body, surgical repair

Question 30

Traumatic Hyphema

Answer 30

= blood in anterior chamber, Complications: risk rebleed @ 3-5 days, risk glaucoma Tx: NO aspirin, surgical evacuation only if 100% + increased ICP

Question 31

Endopthalmitis

Answer 31

*often complication of corneal ulcer = internal infection of eye Tx: intravitreal antibiotics +/- vitrectomy

Question 32

Acute Angle Closure Glaucoma

Answer 32

Sx: acute pain & vision loss w/ halos, frontal headache, nausea, cloudy cornea, & Elevated IOP Pathophys: iris bows to block drainage of aqueous humor Tx: eye drops to reduce IOP + systemic P lowering meds; laser iridotomy *IRReversible if not treated in 1st 24 hrs!

Question 33

Retinal Detachment

Answer 33

Sx: sudden flashes of light & floaters, "curtain over vision," may have normal acuity Risk factors: prior surgery, myopia Tx: surgical repair

Question 34

Non-proliferative vs. Proliferative Diabetic Retinopathy

Answer 34

General Retinopathy: loss of pericytes -> dot-blot hemorrhage -> microaneurysms, hard exudates, nerve fiber layer infactions, venous beading. (ischemia => retinal damage) Proliferative = w/ new blood vessels growing on retina & iris -> vitreous hemorrhage, retinal detachment (w/ scarring).

Question 35

Treatment for (Proliferative) Diabetic Retinopathy

Answer 35

Laser reduction of peripheral retina to decrease O2 need. (aka: photocoagulation)

Question 36

Primary Open Angle Glaucoma

Answer 36

= asymtomatic optic n damage due to high IOP, => slow, chronic loss of peripheral vision Dx: increased cup/disk ratio, high IOP, periph.VF loss Tx: #1 eye drops to suppress aqueous fluid (timolol, a-adrenergics, carbonic anhydrase inhibitors); 2. surgery to increase aqueous outflow

Question 37

Macular Degeneration: non-exudative vs. exudative

Answer 37

*Macular Degen = loss of deep vascular supply to retina Non-exudative ("dry"): gradual loss of central vision, ("drussen"/geographic atrophy) Tx: vitamin supplementation

Question 38

Cataracts - pathophysiology & etiology

Answer 38

*leading cause of blindness in world (but not in USA bc treatable) = yellow/clouding of crystalline lens (bc grows inward for entire life); Causes: #1 Senile, congenital (Emergency!), drug induced, systemic illness

Question 39

Clinical characterization of Cataracts

Answer 39

may be nuclear sclerotic, cortical or posterior subcapsular of lens. Sx: decreased visual acuity, monocular diplopia Tx: surgical extraction & replace w/ new lens

Question 40

Exudative Macular Degeneration

Answer 40

*Macular Degen = loss of deep vascular supply to retina Exudative ("wet"): rapid central vision loss, bc of neovascular subretinal membrane (subretinal hemorrhage) Tx: ant-VEGF meds