Eye Pathology - Martinez

Question 1

There are about 9 different etiologies that contribute to eye pathology. See if you can recall them.

Answer 1

Inborn (congenital)

Trauma

Medication

Infection

Ischemia

Neoplasm

Degeneration

Immune dysfunction

Other (organs, etc)

Question 2

Try to recall the components of the eye exam.

How is the pediatric eye exam approached?

Answer 2

Visual acuity & fields, pupil exam, extraocular movements, intraocular pressure, slit-lamp and fundus exams.

Done under anesthesia (good luck getting a 2yo to fixate). Also get corneal thickness, ultrasound (OCT?), and dilated fundus imaging.

Question 3

Recall the five layers of the cornea.

What functions does it serve?

Answer 3

Epithelium > Bowman’s membrane > Stroma > Descemet’s membrane > Endothelium

It must be transparent, provides the majority of refraction (~50D), and helps maintain structure.

Question 4

What is the composition of the corneal stroma?

What function is served by the corneal endothelium?

Answer 4

Type 1 collagen and keratinocytes, arranged in parallel bundles to preserve transparency.

Pumps out water from the corneal stroma.

Question 5

How does the cornea respond to a superficial injury?

What is the outlook for a deep corneal injury?

Answer 5

Epithelial hyperplasia and full repair.

The outlook for any injury that penetrates the stroma is bad–the repair response will form a scar (Type 4 collagen, blood vessels) that will reduce or destroy vision.

Question 6

Describe the different subtypes of Peter’s anomaly.

Answer 6

Type I - Iridicorneal adhesions

Type II - Corneolenticular adhesions

“Peter’s-Plus” - In association with syndrome of short stature, delayed development, characteristic facial features…

*All feature corneal opacification, often bilateral.

Question 7

What corneal structure is most damaged in Peter’s anomaly?

What can cause it?

Answer 7

The endothelium & Descemet’s membrane.

Can be sporadic, but sometimes seen with PAX6 mutations.

Question 8

Describe the epidemiology of Fuch’s corneal dystrophy.

What would be seen on histology?

Answer 8

Autosomal dominant inheritance, yet has a female predilection. Disease onset in 50s.

Proliferation of endothelium/descemet’s membrane (guttae), eventually progressing to endothelial loss. Thickened cystic stroma, hazy overall.

Question 9

Describe the structure and function of the lens.

Answer 9

The lens is a transparent and biconcave structure suspended by zonule fibers. It is divided into an epithelium, capsule, and fiber cells.

It functions in accommodation–can change shape to facilitate focusing.

Question 10

Describe the internal composition of the lens.

What is a cataract?

Answer 10

Contains highly organized, long & thin cells full of crystallin. Older cells found centrally.

A cataract is a clouding of the lens.

Question 11

What are the ocular consequences of a prenatal rubella infection?

Answer 11

Rubella can infect the fiber cells, causing inappropriate proliferation.

Cataract forms (initially focal, then complete).

Retinopathy results from RPE damage (“Salt & pepper”, vision OK)

Other anomalies (deafness, heart disease, microcephaly, hepatomegaly…review lecture on TORCH)

Question 12

Besides congenital Rubella infection, what else can cause cataracts?

Answer 12

Age (from UV radiation; more or less inevitable!)

Diabetes Mellitus

Trauma

Steroid use

Question 13

What is the function of the retina?

Try to recall its layered structure.

Answer 13

The retina converts light into neuronal impulses. It’s the “seeing” part of the eye.

Comprised of 11 layers (probably don’t need to know them, but: Internal limiting membrane, nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, external limiting membrane, photoreceptor outer & inner layers, retinal pigment epithelium)

Question 14

What is the RPE?

What functions does it serve?

Answer 14

Retinal pigment epithelium; the dark squamous layer deep to the photoreceptor layer.

Absorbs stray light, forms the blood-retinal barrier, supplies nutrients and eliminates waste. Also involved in the retinal cycle (restores all-trans-retinal to 11-cis-retinal by phagocytosing PR outer segments)

Question 15

Besides photoreceptors, what other neurons are present in the retina?

What structures do they ultimately signal to?

Answer 15

Bipolar cells, ganglion cells, horizontal cells, amacrine cells, and Muller cells (glia).

The thalamus, hypothalamus, midbrain, and lateral geniculate nuclei

Question 16

What is retinitis pigmentosa?

What is the most common defect caused?

Answer 16

A broad collection of heritable retinal degenerative conditions.

Discussed in class was a mutation in rhodopsin in which the opsin protein misfolded, reducing outer segment cycling.

Question 17

What is the inheritance pattern of retinitis pigmentosa?

What is it associated with?

Answer 17

As this is a heterogeneous disease, there are variants with just about every inheritance type.

May be isolated, syndromic (eg Usher’s disease), or secondary to other diseases (eg Refsum’s disease)

Question 18

What is the difference between dry and wet AMD?

Answer 18

Dry: Drusen form in the outer retinal layers, causing loss of RPE and photoreceptors.

Wet: Choroidal vessels breach Bruch’s membrane to enter retina, can cause bleeding and further loss.

Question 19

Describe the pathophysiology of Retinopathy of Prematurity.

How can it be treated?

Answer 19

The anterior retina is normally supplied by the central retinal artery; premature birth before this can occur causes abnormalities of the extending vessels which can bleed or cause retinal detachment.

Treatment: Laser therapy (burn the retina in place), anti-VEGF therapy (bevacizumab, presumably)

Question 20

In diabetic retinopathy, hyperglycemia leads to loss of _____ which promotes bleeding–this manifests on fundus imaging as ________. Areas of nonperfused retina produce ______ causing spread of vessels, which may ultimately contract causing ________.

Answer 20

Pericytes

Microaneurysms, dot-blot & flame hemorrhages

VEGF

Retinal detachment

Question 21

Central retinal artery occlusion, also known as CRAO, tends to result from what conditions?

How is its outlook?

Answer 21

Atherosclerosis, especially of the internal carotid artery.

Not great; vision rarely recovers and it signals increased morbidity due to the atherosclerosis.

Question 22

What is the only discussed retinal tumor?

Distinguish between the sporadic and hereditary forms.

What are the distinctive clinical and pathologic findings?

Answer 22

Retinoblastoma

Sporadic is usually unilateral, while hereditary (AD) can be bilateral. Note that both result from loss of the Rb gene on chr 13 (“retinoblastoma is unlucky”)

White pupil reflex and Flexner-Wintersteiner rosettes.

Question 23

What is contained within the optic nerve & tract?

Through what does it exit the orbit?

Answer 23

About a million ganglion fibers, plus glia.

The optic canal/foramen (not the superior orbital fissure)

Question 24

What are some causes of traumatic optic neuropathy?

What can be found on pathology?

Prognosis?

Answer 24

Direct or indirect injury (MVAs, falls, assault) as well as hemorrhagic infarcts.

Loss of the axons. Microgliosis (not astrocytosis?)

Dreadful–the optic nerve does not regenerate.

Question 25

What is glaucoma?

How does it happen?

Consequences?

Answer 25

Increased intraocular pressure.

Increased aqueous humor production or decreased outflow. Note the difference between open-angle and closed-angle (emergency!)

Increased IOP compresses the lamina cribrosa through which the nerve fiber exits, causing ganglion fiber loss there.

Question 26

What are some risk factors for glaucoma?

How can the disease severity be assessed?

Answer 26

IOP (duh), age, race, and corneal thickness apparently.

Assess IOP with tonometry, and retinal function with microperimetry.

Question 27

Recap

Guttae are seen in which disease?

Bevacizumab can be used to treat which diseases?

Answer 27

Guttae are a hallmark of Fuch’s Corneal Dystrophy.

Bevacizumab can be used in retinopathy of prematurity, AMD, DR, actually an assload of retinal pathologies.

Question 28

Recap

What protein facilitates the transparency of the cornea? The lens?

What disease can present with “salt & pepper” retina on fundoscopy?

What is the most common cause of cataracts?

Answer 28

Type 1 Collagen in cornea, Crystallin in lens.

Congenital rubella infection

Age.

Question 29

Review of Neurophys & Anatomy

Describe the pathway taken by retinal impulses to reach the visual cortex.

What extracortical sites receive retinal input?

What would result from lesion of the right optic tract?

Answer 29

Temporal impulses decussate at the optic chiasm. Once at the LGN, fibers segregate by altitude (superior/inferior) and continue through the dorsal or ventral (Meyer’s) radiations to reach the visual cortex.

Pretectal nuclei (part of the pupillary reflex pathway), suprachiasmatic nucleus, and presumably 3-4 other sites.

Right optic tract lesion would cause a contralateral homonymous hemianopia (ie Left half of vision is lost)

Question 30

Review of Neurophys & Anatomy

What do the horizontal cells of the retina do?

Light turns a photoreceptor (ON/OFF), this in turn switches a bipolar cell (ON/OFF), which combine with other bipolar cells to turn a ganglion cell (ON/OFF).

What are the two arterial supplies of the retina?

Answer 30

Horizontal cells are involved in reciprocal inhibition–one photoreceptor being turned on turns off its neighbors.

ON, OFF, ON.

The choroidal arteries and central retinal artery (both branches of the ICA).