CLM - Pathological Changes in High Myopia - Week 7 Flashcards
List the power ranges (huhuhu) associated with the 3 categorical classifications of myopia.
Low - <3.00D
Medium/moderate - -3.00 to -5.75D
High - ≥-6.00D
Define pathological myopia.
Myopia associated with characterisic degenerative changes in the sclera, choroid and RPE, in association with compromised visual function
What is the prevalence of high myopia in Australia?
2%
List 4 myopia associated pathologies.
Retinal abnormalities
-macula
-peripheral
Optic disc pathologies
Scleral abnormalities
Other (cataract)
What is the most common complication of high myopia?
Myopic maculopathy
Define myopic maculopathy. List 4 signs.
Slow prograssive atrophy of the macula
-lacquer cracks
-choroidal neovascularisation
-macular holes
-macular retinochisis
Is myopic maculopathy sight-treatening?
Yes
What is the cause of myopic maculopathy (3)?
Not certain but believed excessive elongation thins retina and choroid + weakened sclera
In what percentage of myopic eyes does myopic maculopathy progress significantly?
40%
What are lacquer cracks in myopic maculopathy?
Spontaneous ruptures in the elastic layer of bruch’s membrane
Are lacquer cracks symptomatic or asymptomatic?
Initially asymptomatic
How do lacquer cracks appear in colour and at the border?
Fine, irregular, yellow lines
Mottled pigment at the border
What is a sudden decrease in VA often associated with in high myopic eyes?
Sub-retinal haemorrhage due to myopic choroidal neovascularisation
In what percentage of high myopic eyes does choroidal neovacularisation occur?
10%
What is the cause of choroidal neovascularisation?
Due to growth of new blood vessels from the choroid
Does choroidal neovascularisation have a good or poor prognosis?
Very poor
What is macular retinoschisis?
Splitting of the neural retina into its inner and outer layers
What two effects does macular retinoschisis have on vision?
Visual distortion and metamorphopsia
What does macular retinoschisis precede?
The formation of a true macular hole
In what percentage of high myopic eyes does macular retinoschisis progress to a true retinal detachment?
20-50%
What can retinal detachment develop secondary to?
A retinal hole (macula hole)
What are macular holes common in eyes with?
Posterior staphyloma
What is the most important peripheral retinal abnormality in high myopic eyes?
Lattice degeneration
What size can lattice degeneration have?
0.5 - 6 DDs
How does lattice degeneration appear?
White criss-crossed lines
What causes lattice degeneration?
RPE hyperplasia
What can vessels be surrounded by in lattice degeneration?
Glial proliferation
What is lattice degeneration accompanied by (2)?
Areas of vitreo-retinal adhesion and retinal thinning
In what percentage of high myopic eyes is lattice degeneration found?
10%
What is the long-term risk of retinal detachment if lattice degeneration is present?
0.5%
What is rhegmatogenous retinal detachment?
Separation of the retina due to a break in the sensory retina
Is glaucoma associated with a higher or lower risk of primary open angle glaucoma? Explain why in terms of how glaucoma affects the eye.
Higher risk (approximately double)
Longer axial length -> greater deformation of the lamina cribrosa
What is posterior staphyloma and why does it occur?
Bulging due to extasia of the globe, as a consequence of excessive axial elongation
What does posterior staphyloma involve regarding the layers of the eye?
Outward protrusion of all the layers of the eye
What does recent data suggest of collagen bundles in the posterior poles in posterior staphyloma?
They may be abbnormal leading to a loss of structural integrity
What does posterior staphyloma predispose one to?
Other pathologies like macular holes and foveoshisis
What is scleral thickness like in high myopic eyes (what layer is affected specifically)?
Thinner, has a much thinner stroma
List 7 architectural differences of scleral bundles in the sclera of high myopic eyes.
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
Overall, how does a myopic sclera compare to an emmetropic sclera in strength?
It is weaker
Is there an association between myopia and cataract (be specific)?
Yes, posterior sub-capsular cataract
Axial length may be the root cause
Does myopia correction prevent resultant myopic pathology?
No
Does laser refractive surgery treat the structural causes of myopia?
No
Are eyes still at risk of myopia-associated pathologies?
Yes
