Patho Exam 2: Ann Olmstead

What is the function of the cornea

allows light to pass through to the interior eyeball, bends

incoming light

What is the function of the sclera

attachment for eye muscles, maintains ocular shape

What is the function of the pupil

opening which allows light to the interior of the eye

What is the function of the lens

fine tunes focus of light to produce a sharp image on the retina

What is the function of uvea

(iris, ciliary body, choroid) vascular, nutrient dense, oxygen

supply

What is the function of the iris

regulates the amount of light that gets through the

pupil by changing the pupil size

What is the function of the choroid

supplies the retina and sclera with blood,

nutrients, oxygen. Also absorbs excess light

What is the function of the ciliary body?

attaches the choroid to the iris, controls the

lens shape, contains ciliary processes-> secrete aqueous humor

What is the function of the anterior chamber

area between the posterior surface of the cornea and anterior surface of the iris

What is the function of aqueous humor

provides nutrients and oxygen to the cornea and lens, maintain intraocular pressure

What is the function of the posterior chamber

area between the posterior surface of the iris and the front of the lens

What is the function of the canal of schlemm

drains the aqueous humor from the anterior chamber into the bloodstream (regulate IOP)

What is the function of the vitreous humor

gel like fluid behind the lens which supports the lens and holds the retina in place

What is the function of retina

contains rods and cones, converts light into signals which travel to the brain

What is the function of the macula

vision acuity, provide sharper images

What is the function of the fovea

center of the area focuses sharpest visual acuity

What is the function of the central retinal A/V

supplies/drains blood in the retina

What is the function of the optic nerve (CN II)

transmits sensory information to the brain

What are the function of the rods

night and peripheral vision

· Low acuity vision-multiple rods connect to one ganglion

· Most dense in peripheral retina

What are the function of cones

color and acuity (clarity or sharpness)

· High acuity-one cone to one ganglion

· Most dense in the center of the retina (macula-> fovea)

What is macular degeneration

Age related degeneration of the macula/fovea causes blurred central

vision

What is dry macular degeneration

o Reduced retinal circulation/debris removal

o Accumulation of drusen (debris)->inflammation

o Slow photoreceptor degeneration

What is wet macular degeneration

o Drusen->inflammation->VEGF activation

o Choroid neovascularization to compensate for

decreased circulation

o New vessels are leaky, easily hemorrhage, form scars

o Fast photoreceptor degeneration

Why does macular degeneration lead to abnormal color differentiation

The macula is highly concentrated with cones which are responsible for color perception. Degeneration destroys cones thus makes color harder to differentiate

Presbyopia

the lens becomes stiff and can not change shape and allow

accommodation

How does artery occlusion cause vision loss and affect the appearance of the retina and macula

retina cannot receive oxygenated blood (ischemia) which causes vision loss. The retina will be pale typically with a cherry red spot (fovea) which has its own blood supply.

Vision loss is sudden, painless, and severe

How does vein occlusion cause vision loss and affect the appearance of the retina and macula

blood cannot leave the retina, increases pressure in the vessels which can cause them to burst and leak into the retina. The retina will have a "blood and thunder" appearance; microhemorrhages, cotton wool spots, edema, and tortuous veins.

Vision loss is sudden, painless, less severe (variable)

How do microaneurysms develop as a result of retinal vascular disease?

small, localized swelling of capillaries

How do neovascularization develop as a result of retinal vascular disease?

new vessels developed to compensate for lack of

oxygen to the retina

How do hemorrhages develop as a result of retinal vascular disease?

ruptured microaneurysms

How do opacities develop as a result of retinal vascular disease?

hard exudates (leaked lipid and protein) and cotton woll spots

(nerve fiber infarcts)

How does non proliferative diabetic retinopathy develop as a result of retinal vascular disease?

high blood glucose damages existing retinal blood vessels leading to microaneurysms

How does proliferative diabetic retinopathy develop as a result of retinal vascular disease?

decreased retinal perfusion causes neovascularization (via VEGF), hemorrhage, and opacities

What is glaucoma

increased ocular pressure due to the blockage of the canal

of Schlemm (drains aqueous humor) which results in the death of retinal

ganglion cells and progressive vision loss (peripheral to central)

What is open angle glaucoma

the aqueous humor fails to drain through the trabecular meshwork resulting in a slow progression of pressure increase and vision loss (this is typically painless)

What is closed angle glaucoma

the canal of Schlemm is physically blocked by the iris, resulting in a rapid increase in IOP which is painful and causes faster

vision loss

How do prolonged periods of darkness trigger an episode of acute angle closure glaucoma

§ Pupil dilation + increased posterior chamber pressure

§ Pushes the iris against the trabecular meshwork and canal of Schlemm

§ Fluid gets stuck in the anterior chamber and increases IOP

How does Rhegmatogenous lead to retinal detachment

vitreous humor accumulates behind the retina

· Trauma, posterior vitreous detachment d/t age related

liquefaction of vitreous humor

How does vitreous traction lead to retinal detachment

strong vitreoretinal adhesion +contraction of fibrous membrane (formed from microtrauma during aging or disease)

How does exudate lead to retinal detachment

fluid accumulation between the retina and back of the eyeball d/t inflammatory conditions or tumors

What is the basic mechanisms of cataract formation

§ Bilateral opacification of the lens from protein deposits

§ Opacification causes light to scatter->blurred vision

What type of cataract formation is a slow progression

· Nuclear: opacification of the central (nucleus) lens

What type of cataract formation is a rapid progression

· Posterior subcapsular: opacification in the posterior cortical layer under the lens capsule

What type of cataract formation leads to mild degeneration

Cortical: opacification of the lens cortex (periphery)

What is vasculitits?

generalized term for inflammation of a blood vessel which

causes vessel fibrosis and wall thickening

· Inflammation can be in one or multiple layers of the vessel

· Caused by damage or autoimmune process

What is giant cell arteritis?

autoimmune vasculitis of the (usually) temporal artery

· Transmural inflammation: effects all three layers of the

blood vessel

o Largely impacts tunica media and interna

§ Giant cells in media

§ Vessel thickening in interna

What is the patho for GCA

· can result in vision changes if the ophthalmic artery is

involved (supplies the central retinal artery)

o artery thickens->ischemia of optic/retinal tissue->tissue

death->loss of function (vision)

What is GCA's common population

· Common in white women over age 50 (peak age 70)

How does GCA present

· Present with severe unilateral HA, vision changes, jaw

claudication

· Strong association with polymyalgia rheumatica (PMR)

inflammatory muscle disease

How is GCA dx

· Dx through temporal artery bx

How is GCA tx

· Tx should start with high dose steroids (usually 60mg) with

long slow taper (faster taper to 10mg then very slow taper off

steroids, roughly 6mo-1yr)