4. The Eye

Question 1

What is the flow of aqueous humor?

Answer 1

1. Epithelium of ciliary muscles (accommodation) make aqueous humor when sympathetic activation ➜
2. Drain into posterior chamber (where its made) ➜
3. through pupil ➜
4. Anterior chamber, through the trabecular meshwork ➜
5. Schlemm canal, where it is drained.

Question 2

What are cataracts?

Answer 2

Congenital or acquired opacification of the lens that is painless, leading to ↓ vision.

Question 3

What can cause cataracts?

Answer 3

1. DM
2. Wilson’s Disease
3. Atopic dermatitis
4. Drugs (esp corticosteroids)
5. Radiation
6. Trauma

Question 4

Age-related cataracts result from what?

Answer 4

Nuclear sclerosis (opacification of the lens nucleus)

Question 5

What are posterior subscapular cataracts?

Answer 5

Migration and hyperplasia of the lens epithelium posterior to the lens.

Question 6

What is it called when the lens becomes opaque by liquifying?

Answer 6

Morgagnian (hypermature) cataract

Question 7

What is phacolysis and what can it cause?

Answer 7

Fix cataract by liquifying the lens ➜ BUT; HMW proteins leak through the capsule

• ➜ clogging the trabecular meshwork
• ➜ ↑ IOP
• ➜ phacolytic glaucoma, a type of open-angle glaucoma.

Question 8

What is glaucoma?

Answer 8

Changes in the visual field and in the cup of the optic nerve, most commonly due to ↑ in IOP caused by aqeuous humor (but some people do have NL or low-tension glaucoma).

Question 9

What are the 2 categories of glaucoma?

Answer 9

• 1. Open-angle glaucoma
• 2. Closed-angle glaucoma

Question 10

What are the differences in open and closed-angle glaucoma?

Answer 10

1. Closed-angle glaucoma: iris is adhered to trabecular meshwork ➜ closing the angle and prevents outflow of aqeuous humor ➜ ↑ IOP.
2. Open-angle glaucoma (MC): angle is open, howevere there is a overproduction or ↓ drainage of aqeuos humor, causing a resistance to outflow ➜ ↑ IOP.

Question 11

Primary open-angle glaucoma is caused by what?

Answer 11

• MYOC mutations in juveniles and adults
• OPTN mutations in some adults.

Question 12

Secondary open-angle glaucoma is caused by what?

Answer 12

• Most commonly by pseudoexfoliation, associated with polymorphisms in LOX1 gene => deposits of fibrous material through the anterior segement

Question 13

RF for Glaucoma

Answer 13

• 1. Age
• 2. Race (African-american and Hispanic)
• 3. FHx
• 4. DM/HTN
• 5. Chronic corticosteroid use (MDI)

Question 14

• What parts of the eye make up the uvea?
• Vascularized/lymphatics?

Answer 14

• Uvea = Iris, choroid, ciliary body
  
  • Highly vascularized, no lymphatics

Question 15

What is the most common primary intraocular cancer in adults?

Answer 15

Uveal Melanoma

Question 16

What mutations are uveal melanomas associated with?

Answer 16

GOF mutations in GNAQ and GNA11 (85%) oncogenes. Uveal nevi are associated with the same oncogenes, however, they RARELY transform to melanomas.

Question 17

How do uveal melanomas spread and where is the first place?

Answer 17

Because the eye does not have lymphatics, uveal melanomas spread hematogenously => liver.

Question 19

What type of uveal melanomas are associated with a worse prognosis?

Answer 19

Epitheliod melanoma cells (spherical, greater cytological atypicality):

1. Larger nuclei
2. Prominent nucleoli
3. Infiltrating plasma cells/lymphocytes

Question 20

What is the morphology of the cornea?

Answer 20

1. PAS+ BM, which separates the epithelium from the acellular Bowman layer
2. PAS+ Descemet membrane facing the vitrous, lined by cells that prevent from fluid from getting into the cornea.

Question 21

Why does rejection NOT occur in corneal transplants?

Answer 21

No BV and lymphatics

Question 22

What is the most common primary intraocular cancer in children?

Answer 22

Retinoblastoma: mutations in RB gene

Question 23

What’s the difference between familial and sporadic retinoblastoma?

Answer 23

• Familial: germline mutation in one RB allele => more often bilateral
• Sporadic: two separate sporadic mutations occur in RB allele

Question 24

Which chromosome is the RB gene found on?

Answer 24

Chr 13q14

Question 25

Retinoblastomas arising due to germline mutation are often ________, compared to people who inherit it sporadically.

Answer 25

Bilateral: inherit 1 abnl gene => but can cause mutaion of NL gene.

Question 26

Retinoblastoma tends to metastasize to what sites?

Answer 26

1. • Brain
2. • Bone marrow
3. • Skull, distal bones, and spinal cord

Question 27

What is the most common route of escape for metastasis to the brain by Retinoblastoma and how does this affect prognosis?

Answer 27

• Via optic nerve
• Poor prognosis

Question 28

When cells of a retinoblastoma shed into the anterior chamber, aggregate and form nodules on the iris or settle inferiorly, this is known as?

Answer 28

Pseudohypopyon

Question 29

Histologic features of a retinoblastoma?

Answer 29

1. Hyperchromatic nuclei that are round, oval, or spindle-shaped w/ scant cytoplasm (small, round blue cells)
2. Flexner-Wintersteiner rosettes (3): single layer of eosinophilic columnar tumor cells around a lumen lined by a refractile structure (external limiting membrane)
   
   1. Homer wright: less common; lumun is filled with eosinophilic cytoplasmic processes
   2. Fleurette: clsters of rods and cones

Question 30

Most common symptoms of Retinoblastoma?

Answer 30

• 1. Leukocoria (white pupillary reflex)
• 2. Strabismus
• 3. Ocular inflammation