Anatomy of the cornea

Question 1

Anatomy of cornea

Answer 1

5 layers Epithelium, bowmans , stroma, desemcents membrane and endothelium

Parallel fibers of type 1 collagen and keratocytes, paralell structure allows for opticla clarity

no vesels o2 and nutrient obtainaed thru tears anteriorly and aqueus humor psoterior, endothelial cells pump out fluid from inside to maintain dehydration

Question 2

Function of cornea

Answer 2

refractic and mechanical strengths

Question 3

Peters anomaly

Answer 3

rare eye malformation resulting in congential corneal opacity, part of spectrum of developmental anomalies of the cornea, iris and lens termed anterior segment dysgenesis

type 1- characterized by central corneal opacity with iridocorneal adhesions

type 2- central opactity and cataracts or coneolensticular adhesion

Peters plus- peters with short, dev delay, dysmorphic face (cleft lip) cardiac, CNS and genital abnormalities

Sporadic or genetic (PAX6), can be bilateral

Question 4

Peters anomoly pathophys

Answer 4

The endothelium and descements membrane dont form correctly (fluid is not removed from the area) leading to opacity

Corneal collagen fibers are disturbed in that area leading to opacity

Question 5

Corneal response to trauma

Answer 5

Injury–> epithelial cell injury and death, disruption of bowmans layer and stromal lamellae, keratocyte injury and death

Question 6

Corneal response to trauma

Answer 6

Corneal repair epithelial hyperplasia, stromal contraction
Epithelial repair, keratocyte activation, synthesis of type 1 collagen, keratan sulfate and type 6 collagen, blood vessel formation

Question 7

Fuchs corneal dystrophy

Answer 7

Autosomal dominant corneal dystrophy, more common in women, affects vision starting in the 50s
dysfunction of cornial endothelial cells with growth of descemets membrane (bumps–guttate)

End stage loss of of endothelial cells

Thickened stroma with fluid filled spaces, cysts in epithelium, hazy cornea

Question 8

Anatomy of the lens

Answer 8

transparent biconvex structure, located behind the pupil, attached in place by zonules

3 parts, lens capsule, epithelium and lens fibers, the newest in the periphery

fibers- long thin transparent cells, arrange intracellular content and dispose of unnecessary organelles

Question 9

rubella cataract

Answer 9

caused by maternal infection by RNA toga virus, infection of lens fibers cells by the virus

Infection of lens fiber cells by virus, lens cells retain nucleus and organelles, pearly white focal nuclear opacification, can progress to complete cataract, live virus can be recovered from lens up to 3 yrs after birth

Question 10

Rubella retinopathy

Answer 10

salt and pepper apearance, due to damage of the the pigmented epithelium layer, vision in most instances is preserved

Question 11

Congenital rubella infection

Answer 11

triad- sensorineural deafness, eye abnormality (70%), congenital heart disease

Other manifestation- microcephaly, hepatomegaly or other liver problems, thrombocytopenia purpura, other bone marrow problems, learning disability

Question 12

adult cataracts

Answer 12

age associated, diabetic, traumatic or post ocular surgery, steroid-induced

Question 13

Anatomy of retina

Answer 13

layer of eye that converts light into a neuronal impulse, in to out- retina, choroid, sclera

Question 14

Function of the retina

Answer 14

function of the photoreceptors- specialized neuron that converts light into neuronal signal

Function of the RPE (retinal pigment epithelium) - nourishes and supports the photoreceptors
Absorption of scattered light, formation of the Blood retina barrier, supply of nutrients to photo receptors and elimination of waste

Phagocytosis of photo receptor outer segments

Question 15

REtinitis pigmintosa

Answer 15

most common form of inherited retinal degeneration
Caused by abnormalities in photoreceptors (rods, followed by cones) and the RPE

Visual impairment usually manifest as night blindness and progressive visual field loss (rods)

1/3000 to 1/5000

Histopathologic studies suggest that RP results from a primary defect in the rod and cones- final common pathway is photo receptor cell death by apoptosis

No risk other than genetics, rhodopsin gene mutation

Question 16

Retinitis pigmentosa

Answer 16

inherited AD, AR and X linked dominant or recessive

3 types- Non-syndromic, syndromic (combined with deafness- Usher syndrome), Secondary to other systemic diseases (refsums disease-abnormal buildup of phytanic acid, a type of Fatty acid)

Question 17

Age related macular degeneration (ARMD)

Answer 17

Degneration of retinal pigment epithelium (RPE), accumulation of drusen excrecences believed to represent byproducts of vision

Dry macular degeneration- progressive accumulatio of drusen

eventually Loss of RPE-> loss of photoreceptors

Wet ARMD- blood vessels from the choroid layer invade the inner most layer (Bruchs membrane) causing disruption and bleeding in the outer layers of the retina

Disruption of normal retina architection–> photoreceptor loss and RPE loss

Question 18

Treatment of armd

Answer 18

vision preservation with injection of antiVEGF

Question 19

Retinopathy of prematurity (ROP)

Answer 19

Abnormal development of the vasculature of the retina in premature infants, increased risk if born <1500 grams or earlier than 30 weeks

occurs in premies born prior to full retinal vascular maturation, factors associated with birth result in halting of normal vascular migration to the peripheral retina

Retinal vessels may grow abnormally (lines, ridges and abnormal neovascularization

If undiagnosed/untreated, retinal and vitreous hemorrhages may occur and the retina detach, untreated and treated retinal detachment portend a poor visual outcome

Question 20

Diabetic retinopathy

Answer 20

Leading cause of blindness for people 20-64 yrs, retinal dysfunction due to hyperglycemia, pericyte loss in retinal capillaries, weak vessels bleeds in the retina

can leed to microaneurysms, dot-blot hemorrages, flame hemorrhages

Question 21

Under perfused retina in Diab ret

Answer 21

underperfused retina secretes vascular endothelial growth factor (VEGf)

Proliferative diabetic retinopathy- abnormal blood vessels grow towards the vitreous and over other structures, fragile blood vessels bleed

Contraction of the abnormal vasculature pulls the retina causing retinal detachment

Question 22

Central retinal artery occlusion

Answer 22

Lack of blood flow through the central retinal artery

Etiology- occlusion of the blood flow in the retinal blood vessel (usually embolic, but can be thrombotic, inflammatory or traumatic)

painless sudden viual loss, cherry red spot on fundus

Question 23

retinoblastoma

Answer 23

cancer of the immature retinal cells, most common malignant tumor of the eye in kids, non heritable heritable
Bilateral = heritable unilateral can be non heritable

AD Ch13 on the Rb1 gene (tumor suppressor protein)

Flexner-Wintersteiner rosettes in retinoblastoma

Question 24

Optic nerve

Answer 24

tCN2 transfers optic to brain

Composed of axons of the retinal ganglion cells and glial cells, optic nerve contains approximately 1 million nerve fibers that end at the lateral geniculate nucleus

sensory and pupillary response control

Question 25

traumatic optic neuropathy

Answer 25

Direct or indirect injury (transmitted shock from orbital impact) to the optic nerve results in traumatic optic neuropathy

Common mechanisms of injury includ car/bike fall and beat

axonal loss via direc trauma or hemorrhagic infarct, compression from a sheat hematoma, loss of astorcyte support after replacement with microglia

Pale- ethambutol alcohol

Glaucoma is another cause

Question 26

Glaucosa

Answer 26

Progressve optic neuropathy due to slow loss of optic nerve fibers, risk factors- intraocular pressure, age, central corneal thickness, ethnicity