BS - Myopia (Nature) - Week 8

Question 1

What is the most common eye disorder?

Answer 1

Myopia

Question 2

What percentage of Westerners and Asians does myopia affect?

Answer 2

30% of Westerners, and up to 80% of some Asian populations

Question 3

What structural changes is myopia associated with?

Answer 3

Axial length of the eye.

Question 4

Name 3 conditions that are associated with myopia.

Answer 4

ARMD, retinal detachment, and glaucoma.

Question 5

What is considered to be high myopia, and what axial length?

Answer 5

-6.00D, or axial length over 26.5mm

Question 6

Why is retinal detachment associated with myopia?

Answer 6

“Stretched eyeball, stretched retina”

Question 7

Describe the current prevailing theory for the mechanism underlying myopia (3).

Answer 7

• Ocular growth triggered by a visually evoked signalling cascade (retina).
• Signalling cascade traverses the RPE and choroid and terminates in the sclera.
• Remodelling of the scleral ECM promotes elongation of the eye.

Question 8

Consider an elongated eye. Describe the myopic and hyperopic state of the retina.

Answer 8

It would have central myopia, and peripheral hyperopia.

Question 9

Consider twins, mono and dizygotic, and siblings. What is the concordance for myopia between these relationships? What does this suggest?

Answer 9

A high concordance for twins (mono > dizygotic) and siblings, suggesting high heritability, but also some environmental impact.

Question 10

By what percentage is heritability decreased by environmental factors among inter-sibling correlation for myopia?

Answer 10

0.5%

Question 11

What genetic transmission types does myopia fall under?

Answer 11

Autosomal dominant
Autosomal recessive
X-linked recessive

Question 12

What 6 ocular features is associated with children of high myopic parents?

Answer 12

Higher prevalence of myopia
High Rx of myopia
High axial length
High vitreous chamber depth
Higher dioptre progression
Higher axial length growth

Question 13

Consider the genes implicated in myopia. What 5 pathways and mechanisms are associated with them?

Answer 13

Nueurotransmission
Ion transport
Retinoic acid transport
ECM remodelling
Eye development

Question 14

Consider a child with high myopic parents. How many times more likely is the child to be myopic?

Answer 14

2x to 8x

Question 15

What can be said of the eyes of children of high myopic parents?

Answer 15

They have longer eyes even before they become myopic

Question 16

Are children more likely to be myopic if both their parents are also myopic, or is there no difference between one parent and both being myopic?
Is this effect more pronounced between populations or is it equal?

Answer 16

2 myopic parents means higher chance of being myopic.

More pronounced in Asian populations vs Western

Question 17

Is there a higher correlation between siblings or between children and parents for myopia?

Answer 17

Between siblings

Question 18

What is the most common form of myopia genetic transmission? What dioptre is it associated with?

Answer 18

Autosomal dominant

Mostly -6.ooD or more

Question 19

Name 7 syndromes associated with myopia, and the mode of transmission.

Answer 19

Marfan
Stickler
Wagner
Albinism
Aland Island eye disease
Night blindness
Bornholm eye disease
All are x-linked recessive

Question 20

Describe 7 pathologies of Bornholm eye disease.

Answer 20

Protan defect
Deutan defect
Abnormal cone response
High myopia
High cyl
ON hypoplasia
Normal to slightly reduced VA