Corneal Dystrophies

Question 1

What are the five layers of the cornea?

Answer 1

Corneal Epithelium

Bowman’s membrane

Corneal Stroma

Descements Membrane

Corneal Endothelium

Question 2

Which layers of the cornea do we mainly have a problem with, if any?

Answer 2

Corneal Epithelium

Corneal Stroma

Corneal Endothelium

Question 3

What is Epithelial basement mebrane dystrophy?

Answer 3

The epithelium is very weak and doesn’t stick to bowman’s layer underneath.

Question 4

What are the symptoms associated with a scratch on the cornea if a patient has Epithelial basement membrane dystrophy?

Answer 4

Pain

Watering - epiphora

Photophobia + glare

Waking with a painful eye

Question 5

How may epithelial basement membrane dystrophy appear under a slit lamp?

Answer 5

Epithelial Micro-cysts

As tiny dots or ‘cogans’ in the corneal epithelium - these are basically patches where the cornea has healed itself following any abrasions.

Question 6

What is the acute management of a nasty scratch on the cornea?

Answer 6

Anaesthetics - for the pain

Antibiotics - as a preventative measure

Perhaps mydriatics and cyloplegics to rest the eye - when there is a scratch on the cornea the ciliary muscle goes into spasm.

Perhaps a bandage contact lenses

Question 7

How would we manage recurrent epithelial erosion syndrome (i.e. recurrent damage of the epithelium because it is weak)?

Answer 7

• Debridement - basically take off the current epithelium which is already loose and hope that a new stronger one grows back.(OLD METHOD)
• Anterior stromal puncture - puncture holes in the corneal eptihelium so the bowman’s layer has something to stick onto. (OLD METHOD)
• Excimer laser PTK (phototherapeutic keratectomy)- resurfaces the cornea - it makes the cells of the bownman’s layer rougher so when epithelial cells regrow they have something to stick to. (CURRENTLY USED)

Question 8

What is Reiss Buckler’s?

Is it unilateral or bilateral?

Is it common or rare?

What is it caused by?

Answer 8

A type of corneal dystrophy that affects the bowman’s membrane - it is caused by an autosomal dominant inheritance.

It is unilateral

It is very rare.

It is caused by abnormal collagen

Question 9

True or False- Dystrophies are inherited conditions.

Answer 9

True

Question 10

What are dystrophies?

Answer 10

Abnormal deposition of naturally occuring substances

Question 11

What condition can be seen in the image below?

In whom is this condition prevalent?

What is this condition the result of?

What does this condition indicate?

Answer 11

Arcus Senilis

Those over the age of 50

This condition is the result of deposits of cholesterol esters and glycerides in the stroma

Indicates Raised Chloesterol

Question 12

What do you need to know about granular dystrophy?

Answer 12

It is very rare.

Essentially granular deposits.

It is hereditary

Question 13

What is macular dystrophy and what do you need to know about it?

Answer 13

Diffuse dots all across the surface of the cornea.

it is caused by an excess of naturally occuring material.

It is autosomal recessive.

[Macular is just latin for space]

Question 14

What type of dystrophy is this and what is it caused by?

Answer 14

It is lattice dystrophy. It is an autosomal domiant condition. It is caused by a network of deposits.

It is a rare condition

[Despite having a corneal regraft it still reoccurs].

Question 15

What condition is this?

Answer 15

Gelatinous Droplet Keratopathy

It is autsomal recessive.

Caused by Amyloid inbalance.

Question 16

Whta type of dystrophy is this and what is it caused by?

Answer 16

VERY VERY RARE

Question 17

What does corneal Ectasia mean?

Answer 17

The cornea is buldging aka it is coming forward

Question 18

What is another name for corneal ectasia?

Answer 18

Keratoconus

Question 19

How may keratoconus be identified via retinoscopy and slit lamp?

Answer 19

As a scissor reflex in retinoscopy and an oil droplet flashback through ophthalmoscopy.

Question 20

What is the aetiology of Keratoconus?

Answer 20

udefective collagen cross-linking?

uincreased collagenolysis

• reduced protein synthesis
• defects in RNA translation
• increased corneal compliance

ucorneal hysteresis

-iatrogenic – caused by LASIK laser eye surgery – this is where they take away parts of the cornea – if they take away too much they leave the px at risk of keratoconus – which occurs when the cornea is very thin and so susceptible to distortion.

Question 21

What are some associations of Keratoconus?

Answer 21

Px with the following conditions are more likely to have keratoconus:

• atopic disease: vernal conjunctivitis, eczema, asthma
• Down’s syndrome (trisomy 21)
• eye rubbing
• aniridia (congenital condition where you are missing the iris)
• Retinitis pigmentosa
• Leber’s congenital amaurosis
• ectopia lentis
• microcornea
• blue sclera – osteogenesis imperfecta………………..

Question 22

What are signs of keratoconus?

Answer 22

Question 23

What is the managment of keratoconus?

Answer 23

• Spectacles – however VA limited by irregular astigmatism
• Gas Permeable Contact lenses succeed in 85% of cases
• Collagen Cross-Linking (CCL, CXL, CCXL) – method of strengthening the corneea
• Intacs to ‘reinforce’ mid-peripheral stroma

Corneal grafting

Question 24

True or False- In corneal grafts the entire cornea is removed and replaced

Answer 24

False - typically only the central 8mm are removed and replaced (the average cornea is 10-11mm wide).

Question 25

What is a keratoplasty?

Answer 25

A fancy way of saying a corneal regraft

Question 26

What is the difference between a pentrating keratoplasty and a deep lamellar keratoplasty (DLK)?

Answer 26

In a pentrating keratoplasty all of the central cornea is cut out and replaced. In a deep lamellar keratoplasty, the central cornea is cut out but the bottom endothelium isn’t and the new graft is placed ontop of that.

Question 27

What are possible advnatges of a deep lamellar keratoplasty?

Answer 27

Question 28

Do we need to worry about rejection with a corneal graft?

Answer 28

No thankfully not as there are no blood vessels in the cornea to bring the antibodies in

Question 29

What is a site of immune priviledge?

Answer 29

Sites that are able to tolerate introducing antigens without eliciating an inflammatory reaction - basically where risk of rejection is low

(i.e. the cornea)

Question 30

What are some examples of endothelial dystrophies?

Answer 30

• Congenital Hereditary Endothelial Dystrophy (CHED)
• Posterior polymorphous dystrophy (PPD)
• Irido-corneal endothelial dystrophy (ICE)
• Fuchs’ endothelial dystrophy

Question 31

Describe Posterior Polymorphous Dystrophy

Answer 31

Basically what appears to be tram lines in the endothelium.

It does not affect vision and so no treatment is needed.

It is autosomal dominant or recessive.

Question 32

Describe fuchs’ endothelial dystrophy and symptoms associated with it.

Answer 32

Autosomal dominant

• Cornea guttata - (gutattata is latin for droplets)
• Px experiences a loss of endothelial cells
• pax is middle-age onwards
• px expereinces stromal oedema
• there isincreased corneal thickness
• epithelial oedema is present
• visual loss
• erosion symptoms (so ephiphora, photophobia, glare pain etc)

Question 33

What is the managment for Fuchs Endothelial dystrophy?

Answer 33

• dry the cornea – ‘hairdryer’ or 5% NaCl drops
• bandage contact lenses
• reduce IOP
• replace endothelium (PK, Descemet’s stripping automated endothelial keratoplasty DSAEK, Descemet’s membrane endothelial keratoplasty DMEK)