BS - Myopia (Nature) - Week 8 Flashcards
What is the most common eye disorder?
Myopia
What percentage of Westerners and Asians does myopia affect?
30% of Westerners, and up to 80% of some Asian populations
What structural changes is myopia associated with?
Axial length of the eye.
Name 3 conditions that are associated with myopia.
ARMD, retinal detachment, and glaucoma.
What is considered to be high myopia, and what axial length?
-6.00D, or axial length over 26.5mm
Why is retinal detachment associated with myopia?
“Stretched eyeball, stretched retina”
Describe the current prevailing theory for the mechanism underlying myopia (3).
- 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.
Consider an elongated eye. Describe the myopic and hyperopic state of the retina.
It would have central myopia, and peripheral hyperopia.
Consider twins, mono and dizygotic, and siblings. What is the concordance for myopia between these relationships? What does this suggest?
A high concordance for twins (mono > dizygotic) and siblings, suggesting high heritability, but also some environmental impact.
By what percentage is heritability decreased by environmental factors among inter-sibling correlation for myopia?
0.5%
What genetic transmission types does myopia fall under?
Autosomal dominant
Autosomal recessive
X-linked recessive
What 6 ocular features is associated with children of high myopic parents?
Higher prevalence of myopia High Rx of myopia High axial length High vitreous chamber depth Higher dioptre progression Higher axial length growth
Consider the genes implicated in myopia. What 5 pathways and mechanisms are associated with them?
Nueurotransmission Ion transport Retinoic acid transport ECM remodelling Eye development
Consider a child with high myopic parents. How many times more likely is the child to be myopic?
2x to 8x
What can be said of the eyes of children of high myopic parents?
They have longer eyes even before they become myopic
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?
2 myopic parents means higher chance of being myopic.
More pronounced in Asian populations vs Western
Is there a higher correlation between siblings or between children and parents for myopia?
Between siblings
What is the most common form of myopia genetic transmission? What dioptre is it associated with?
Autosomal dominant
Mostly -6.ooD or more
Name 7 syndromes associated with myopia, and the mode of transmission.
Marfan Stickler Wagner Albinism Aland Island eye disease Night blindness Bornholm eye disease All are x-linked recessive
Describe 7 pathologies of Bornholm eye disease.
Protan defect Deutan defect Abnormal cone response High myopia High cyl ON hypoplasia Normal to slightly reduced VA
