10. M II - Pathological Changes in Myopia

Question 1

What is the definition of pathological myopia?

Answer 1

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

Question 2

Myopia categorical classification by degree:
* Low <...DS
* Moderate ... to ...D
* High ≥ ...D

Answer 2

Myopia categorical classification by degree:
* Low <-3.00DS
* Moderate -3.00 to -5.75D
* High ≥ -6.00D

Question 3

Which regions are expected to have the highest prevalence of myopia between 2000 and 2050?

Answer 3

East Asia > North America > Western Europe > Australia > Southern Latin America > North Africa & Middle East > Sub-Saharan Africa

Question 4

What are the expected prevalence of myopia and high myopia in % by 2050?

Answer 4

Myopia = 49.8%
High myopia = 9.8%

Question 5

Myopic ... is the most common complication of high myopia. It has a prevalence of ... to ...% of myopes. This is the ..., which has presentations of lacquer ..., choroidal ..., macular ... and macular .... The cause of this condition is possibly the ... of the eyeball, causing ... of the retina and choroid, and the ... of the sclera. Risk factors of this includes high Rx, ..., older age and .... This condition progresses significantly in about ...% of highly myopic eyes. It is also the 4th most common cause of ... in the UK, which is above ....

Answer 5

Myopic maculopathy is the most common complication of high myopia. It has a prevalence of 0.2 to 0.4% of myopes. This is the slowly progressive atrophy of the macula, which has presentations of lacquer cracks, choroidal neovascularisation, macular hole and macular retinoschisis. The cause of this condition is possibly the excessive elongation of the eyeball, causing thinning of the retina and choroid, and the weakening of the sclera. Risk factors of this includes high Rx, longer axial length, older age and thinner choroid. This condition progresses significantly in about 40% of highly myopic eyes. It is also the 4th most common cause of visual impairment in the UK, which is above diabetic retinopathy.

Question 6

How high of myopia does the prevalence of myopic maculopathy dramatically increase?

Answer 6

> -5.00D, the risk of myopia maculopathy dramatically increase, where less than -5D prevalence is 0.42% and above -5D prevalence is 25.3%.
When above -9.00D, prevalence is over 50%.

Question 7

4 Categories of Myopic Maculopathy:

Category 1 = ... Fundus
* patchiness due to reduction of ... ∴ ... more easily seen
* thinning of the ... and ...
* this may be a normal observation in ...
* No visual effects

Category 2 = ... atrophy
* Posterior pole appears ...
* Extensive loss of ...
* Extent of diffuse atrophy can vary
* ... should be estimated and recorded

Answer 7

4 Categories of Myopic Maculopathy:

Category 1 = Tesselated Fundus
* patchiness due to reduction of pigment ∴ choroidal vessels more easily seen
* thinning of the RPE and choriocapillaris
* this may be a normal observation in aging
* No visual effects

Category 2 = Diffuse chorioretinal atrophy
* Posterior pole appears yellow/white
* Extensive loss of pigment
* Extent of diffuse atrophy can vary
* Size of atrophic area should be estimated and recorded

Question 8

Categroy 3 = ... atrophy
* ... lesions
* Variable ...
*... loss of ... and can progress to loss of ... + ...

Category 4 = ...
* Well defined, round, white ...
* Typically appears around a ...
* Generally centre onto the ... and is ... in shape

Answer 8

Categroy 3 = Patchy chorioretinal atrophy
* Well demarcated white lesions
* Variable size
*Complete loss of choriocapillaris and can progress to loss of outer retina + RPE

Category 4 = Macular atrophy
* Well defined, round, white chorioretinal lesion
* Typically appears around a regressed neovascular membrane
* Generally centre onto the fovea and is round in shape

Question 9

Lacquer cracks are one of the ... of myopic maculopathy. They are .... ruptures in the ... layer of the .... This has a prevalence of ...% of eyes with axial length >...mm. Px initially will be ... and present with ... with mottled pigment at ..... Px may experience sudden ... often associated with ... due to myopic ....

Answer 9

Lacquer cracks are one of the plus lesions of myopic maculopathy. They are spontaneous ruptures in the elastic layer of the Bruch's membrane. This has a prevalence of 4.2% of eyes with axial length >26.5mm. Px initially will be asymptomatic and present with fine, irregular yellow lines with mottled pigment at borders. Px may experience sudden decrease in VA often associated with subretinal haemorrhage due to myopic choroidal neovascularisation.

Question 10

The risk of developing myopic ... increases substantially with increasing ... of myopic maculopathy.
Category 1 has ...% → Category 2 has ...% → Category 3 has ...%.
There are no established ... for CNV and practitioners should focus on ...., including ... and ... and ... intervention. Prognosis of myopic maculopathy is poor, with ...% patients with marked ... within 5 years.

Answer 10

The risk of developing myopic choroidal neovascularisation increases substantially with increasing categoriesof myopic maculopathy.
Category 1 has 0.4% → Category 2 has 1.6% → Category 3 has 2.7%.
There are no established treatments for CNV and practitioners should focus on prevention, including antiVEGF treatment and laser and surgical intervention. Prognosis of myopic maculopathy is poor, with 89% patients with marked visual impairment within 5 years.

Question 11

Fuch’s spot is a ... spot that represents the ... phase of myopic .... This lesion is ... and the fibre vascular membrane becomes ... and .... This forms a ... scar that is sometimes associated with pigmentation.

Answer 11

Fuch’s spot is a pigmented spot that represents the scarring phase of myopic choroidal neovascularisation. This lesion is dry and the fibre vascular membrane becomes reduced in size and flattens. This forms a greyish white scar that is sometimes associated with pigmentation.

Question 12

Macular ... is the splitting/ ... of the ... into its ... and .... This causes visual ..., also known as .... This also occurs before a true ... forms. There is a ...% chance that this will progress to a true ....

Answer 12

Macular Retinoschisis is the splitting/ schisis of the neural retina into its outer and inner layers. This causes visual distortion, also known as metamorphopsia. This also occurs before a true macular hole forms. There is a 20-50% chance that this will progress to a true retinal detachment.

Question 13

What is a macula hole? How may a macula hole progress into retinal detachment?

Answer 13

Macula hole is a defect of the entire neural retina at the macula. Fluid may rush into the hole, causing the retina to peel off = retinal detachment. This is common in eyes with posterior staphyloma, which is the outpouching of the entire globe. Severe visual impairment is common.

Question 14

What do highly myopic eyes have a significantly higher risk of? Which one is the most important out of them?

Answer 14

Highly myopic eyes have a significantly higher risk of peripheral retinal degenerations. Lattice degeneration is the most important.

Question 15

Lattice degeneration can vary between ...DD in size. They present as ..., which is a result of ... and ... hyperplasia. This is accompanied by areas of ... and .... The surrounding retina needs careful assessment for .... This is observed in around ...% of the population. The long term risk of retinal detachment is ...%. ... treatment can be done to minimise further complications.

Answer 15

Lattice degeneration can vary between 0.5-6DD in size. They present as white criss-crossed lines/ lattice, which is a result of abnormal glial cell proliferation and RPE hyperplasia. This is accompanied by areas of vitreo-retinal adhesion and retinal thinning. The surrounding retina needs careful assessment for tears/ holes. This is observed in around 10% of the population. The long term risk of retinal detachment is 0.5%. Laser treatment can be done to minimise further complications.

Question 16

What is rhegmatogenous retinal detachment?

Answer 16

Separation of the retina due to a break in the sensory retina. This is often due to having a hole/ tear in the sensory retina, therefore fluid builds up there and cause the surface of the retina to detach. Risk of detachment increases with increasing myopia.

Question 17

Myopia has a significant association with .... The longer ... and ... causes a greater deformation of the .... This therefore contribute to a higher susceptibility to .... individuals with any myopia have approximately ... of developing ... compared with individuals without myopia. There is also elevated ... with high myopia (≥ -3.00D) and also higher chance of having ....

Answer 17

Myopia has a significant association with open angle glaucoma. The longer axial length and vitreous chamber depth causes a greater deformation of the lamina cribosa. This therefore contribute to a higher susceptibility to glaucomatous optic disc change. individuals with any myopia have approximately double risk of developing open angle glaucoma compared with individuals without myopia. There is also elevated glaucoma risk with high myopia (≥ -3.00D) and also higher chance of having retinal complications.

Question 18

Posterior staphyloma is the bulging of the eye due to ... and as a consequence of excessive .... This involves the outward protrusion of .... Experimental studies suggest that the ... in the posterior pole may be abnormal, causing the loss of .... This predisposes to other ocular pathologies, such as ..., retinal detachment and ....

Answer 18

Posterior staphyloma is the bulging of the eye due to ectasia of the globe and as a consequence of excessive axial elongation. This involves the outward protrusion of all layers of the eye. Experimental studies suggest that the organisation of the collagen bundles in the posterior pole may be abnormal, causing the loss of structural integrity. This predisposes to other ocular pathologies, such as macula hole, retinal detachment and foveoschisis.

Question 19

Which part of the myopic sclera has the most significant difference in thickness compared to emmetropic sclera?

Answer 19

In the posterior pole.
Emmetropic = 0.66
Myopic = 0.233.

Question 20

In high myopia, the architecture of the ... is altered.
* Loss of ...
* Reduced number and thinning of ...
* Loose/ irregular fibre arrangement & ... of bundles
* Reduced number of ... and ...
* Reduced ... diameter
* Trend of ... from ... to ... sclera is lost
* Myopic sclera is ... than emmetropic sclera
* The ... has the most compromised alteration

Answer 20

In high myopia, the architecture of the scleral bundles is altered.
* Loss of longitudinal striations
* Reduced number and thinning of lamellae
* Loose/ irregular fibre arrangement & Dissociation of bundles
* Reduced number of cells and melanocytes
* Reduced scleral fibril diameter
* Trend of reducing collagen fibril diameter from outer to inner sclera is lost
* Myopic sclera is weaker than emmetropic sclera
* The outer sclera has the most compromised alteration

Question 21

Biochemistry changes in myopic sclera:
* Increased levels of ... (...)
* Reduced levels of ... (GAGs) → ..., dermatan sulfate, ..., heparin sulfate → involved in collagen ... and influence ... and ....

Answer 21

Biochemistry changes in myopic sclera:
* Increased levels of Matrix Metalloproteinases (MMP-2)
* Reduced levels of glycosaminoglycans (GAGs) → chondroitin sulfate, dermatan sulfate, hyaluronic acid, heparin sulfate → involved in collagen fibrillogenesis and influence collagen size and organisation.

Question 22

Nuclear cataracts associates with ... shifts. There are also evidence of ... cataract associate with myopes who have ... (<20yo). Eyes with ... cataract tend to have ..., thinner ... and longer .... ... is thought to be the root cause of the association between myopia and .... There are also speculation that a longer ... induces cataracts.

Answer 22

Nuclear cataracts associates with myopic shifts. There are also evidence of posterior subcapsular cataract associate with myopes who have early onsets (<20yo). Eyes with posterior subcapsular cataract tend to have deeper anterior chambers, thinner lenses and longer vitreous cavities. Axial length is thought to be the root cause of the association between myopia and PSC. There are also speculation that a longer vitreous cavity induces cataracts.

Question 23

What is the common misconception of myopic correction and laser refractive surgery?

Answer 23

Myopic correction, including laser refractive surgery does not prevent resultant myopic pathology. The structures remains elongated and mishapen. Therefore these eyes are still at risk of myopia-associated pathologies.

Question 24

What are the public health implications of myopia?

Answer 24

Myopia is the dominant risk factor for retinal detachment and myopic maculopathy etc. It also stands as important secondary risk factor to cataract and glaucoma, second to age. Myopia poses an equal or even greater to risk to ocular as hypertension does for cardiovascular health.