Cornea

Question 1

What fraction of the external eye does the Cornea make-up?

Answer 1

1/6

Question 2

What are the 5 Histological layers of the Cornea?

[Top to Bottom]

Answer 2

Epithelium (+Basement membrane,Stratified squamous) 
Bowman's layer 
Stroma
Descemet's membrane
Endothelium

Question 3

Where does the Cornea get its nutrients from?

Answer 3

Limbal vessels, tear film and aqueous humour

Question 4

Whats the blood supply of the cornea?

Answer 4

AVASCULAR BLOOD SUPPLY

Question 5

Whats the reflective power of the cornea?

Answer 5

40-44 D

Question 6

What are the vertical and horizontal measurements of the cornea?

Answer 6

Transverse oval
Vertically - 11.7mm
Horizontal - 12.6mm
Centrally - 555 MicroM

Question 7

Symptoms from loss of nerve innervation to cornea?

Answer 7

Reduced blinking
Reduce tear production
Reduce epithelial proliferation

Question 8

Which nerve innovates the Cornea?

Answer 8

CN 5 - Ophthalmic division via Long Hillary nerves.

Question 9

When is the corneal shape flattest?

Answer 9

In the morning due to changes in eyelid pressure.

Question 10

Acanthomoeba Keratitis.

PRIMARY POINTS

Answer 10

Aetiology
Eye exposure to soil or contaminated water
Tap water (Cleaning contacts)

Agar - Non-nutrient w/e-coli

Characteristic Late Signs - Perinuerual Inflitarates + Ring-shaped stromal infiltrates.

Tx - Topical Chlorohexadine/ Polyhexamtheylen Biguanide

Question 11

What type of collagen is found in the Sclera?

Answer 11

Type 1

Question 12

What tissue does LASIK and LASEK target?

Answer 12

Central Corneal Tissue ablation - Myopic Eyes (Flatter central cornea)

Peripheral Corneal Tissue ablation - Hypermetropic Eyes (Steeper central cornea)

Question 13

What is the refractive power of lens and cornea?

Which is stronger

Answer 13

Cornea 40D

Lens 20D

Question 14

Which group of individuals are most susceptible to corneal ulcers?

Answer 14

Contact Lens wearers.

Question 15

Clinical features of Corneal ulcers?

Answer 15

eye pain
photophobia
watering of eye
focal fluorescein staining of the cornea

Question 16

Bacterial Keratitis

Most Common causative agents?

Answer 16

Pseudomonas Aureginosa [Contacts wearers]

Staphylococcus aureus

Question 17

Exposure to soil can lead to what form of keratitis?

Answer 17

Acanthamoebic keratitis (Soil/ Contaminated Water)

Question 18

Define Keratitis?

Answer 18

Inflammation for the cornea.

Question 19

What 1 major red flag warrants ophthalmology referral of a contact lens wearer.

Answer 19

Presenting with a painful red eye.

Same-day referral to rule out microbial keratitis