CLM - Pathological Changes in High Myopia - Week 7

Question 1

List the power ranges (huhuhu) associated with the 3 categorical classifications of myopia.

Answer 1

Low - <3.00D
Medium/moderate - -3.00 to -5.75D
High - ≥-6.00D

Question 2

Define pathological myopia.

Answer 2

Myopia associated with characterisic degenerative changes in the sclera, choroid and RPE, in association with compromised visual function

Question 3

What is the prevalence of high myopia in Australia?

Answer 3

2%

Question 4

List 4 myopia associated pathologies.

Answer 4

Retinal abnormalities
-macula
-peripheral
Optic disc pathologies
Scleral abnormalities
Other (cataract)

Question 5

What is the most common complication of high myopia?

Answer 5

Myopic maculopathy

Question 6

Define myopic maculopathy. List 4 signs.

Answer 6

Slow prograssive atrophy of the macula

• lacquer cracks
• choroidal neovascularisation
• macular holes
• macular retinochisis

Question 7

Is myopic maculopathy sight-treatening?

Answer 7

Yes

Question 8

What is the cause of myopic maculopathy (3)?

Answer 8

Not certain but believed excessive elongation thins retina and choroid + weakened sclera

Question 9

In what percentage of myopic eyes does myopic maculopathy progress significantly?

Answer 9

40%

Question 10

What are lacquer cracks in myopic maculopathy?

Answer 10

Spontaneous ruptures in the elastic layer of bruch’s membrane

Question 11

Are lacquer cracks symptomatic or asymptomatic?

Answer 11

Initially asymptomatic

Question 12

How do lacquer cracks appear in colour and at the border?

Answer 12

Fine, irregular, yellow lines

Mottled pigment at the border

Question 13

What is a sudden decrease in VA often associated with in high myopic eyes?

Answer 13

Sub-retinal haemorrhage due to myopic choroidal neovascularisation

Question 14

In what percentage of high myopic eyes does choroidal neovacularisation occur?

Answer 14

10%

Question 15

What is the cause of choroidal neovascularisation?

Answer 15

Due to growth of new blood vessels from the choroid

Question 16

Does choroidal neovascularisation have a good or poor prognosis?

Answer 16

Very poor

Question 17

What is macular retinoschisis?

Answer 17

Splitting of the neural retina into its inner and outer layers

Question 18

What two effects does macular retinoschisis have on vision?

Answer 18

Visual distortion and metamorphopsia

Question 19

What does macular retinoschisis precede?

Answer 19

The formation of a true macular hole

Question 20

In what percentage of high myopic eyes does macular retinoschisis progress to a true retinal detachment?

Answer 20

20-50%

Question 21

What can retinal detachment develop secondary to?

Answer 21

A retinal hole (macula hole)

Question 22

What are macular holes common in eyes with?

Answer 22

Posterior staphyloma

Question 23

What is the most important peripheral retinal abnormality in high myopic eyes?

Answer 23

Lattice degeneration

Question 24

What size can lattice degeneration have?

Answer 24

0.5 - 6 DDs

Question 25

How does lattice degeneration appear?

Answer 25

White criss-crossed lines

Question 26

What causes lattice degeneration?

Answer 26

RPE hyperplasia

Question 27

What can vessels be surrounded by in lattice degeneration?

Answer 27

Glial proliferation

Question 28

What is lattice degeneration accompanied by (2)?

Answer 28

Areas of vitreo-retinal adhesion and retinal thinning

Question 29

In what percentage of high myopic eyes is lattice degeneration found?

Answer 29

10%

Question 30

What is the long-term risk of retinal detachment if lattice degeneration is present?

Answer 30

0.5%

Question 31

What is rhegmatogenous retinal detachment?

Answer 31

Separation of the retina due to a break in the sensory retina

Question 32

Is glaucoma associated with a higher or lower risk of primary open angle glaucoma? Explain why in terms of how glaucoma affects the eye.

Answer 32

``` Higher risk (approximately double) Longer axial length -> greater deformation of the lamina cribrosa ```

Question 33

What is posterior staphyloma and why does it occur?

Answer 33

Bulging due to extasia of the globe, as a consequence of excessive axial elongation

Question 34

What does posterior staphyloma involve regarding the layers of the eye?

Answer 34

Outward protrusion of all the layers of the eye

Question 35

What does recent data suggest of collagen bundles in the posterior poles in posterior staphyloma?

Answer 35

They may be abbnormal leading to a loss of structural integrity

Question 36

What does posterior staphyloma predispose one to?

Answer 36

Other pathologies like macular holes and foveoshisis

Question 37

What is scleral thickness like in high myopic eyes (what layer is affected specifically)?

Answer 37

Thinner, has a much thinner stroma

Question 38

List 7 architectural differences of scleral bundles in the sclera of high myopic eyes.

Answer 38

``` Loss of longitudinal striations Dissociation of bundles from each other Reduced number of lamellae Thinning of lamellae Loose/irregular fibre arrangement Reduced number of cells and melanocytes Reduced scleral fibril diameter ```

Question 39

Overall, how does a myopic sclera compare to an emmetropic sclera in strength?

Answer 39

It is weaker

Question 40

Is there an association between myopia and cataract (be specific)?

Answer 40

Yes, posterior sub-capsular cataract | Axial length may be the root cause

Question 41

Does myopia correction prevent resultant myopic pathology?

Answer 41

No

Question 42

Does laser refractive surgery treat the structural causes of myopia?

Answer 42

No

Question 43

Are eyes still at risk of myopia-associated pathologies?

Answer 43

Yes