Emmetropization

Question 1

What is it?

Answer 1

Emmetropization is the process by which the refractive state of the eye changes and is mostly complete by 3 years old, from birth.
-Its the reduction in mostly hypermetropia and astigmatism and can eradicate around +3.00 DS and +1.50 DC (asigmatism)

Question 2

Emmetropization is governed by both active and passive factors

Answer 2

Passive emmetropization refers to normal eye growth as eye size increases, power of optical components decreases and proportionally refractive error decreases.
-Active emmatropisation decribes the visual feedback mechanism in the control of eye growth (feedback from eye which is blur and stimulates cortex to keep/stop growing the eye)

Question 3

The critical period

Answer 3

The Critical period is where vision and BV connections are being rapidly formed and this period lasts until roughly 2 y/o. Any disruption during this time can have a severe effect on the overall visual outcome.
-The sensitive period is when the visual system is still developing therefore disruptions can still have an effect on the overall visual outcome but are not as severe, and lasts up to 8-10 y/o.
-The earlier the deprivation, the more severe the visual loss.

Question 4

Amblyopia links

Answer 4

Amblyopia exists when the process of emmetropization has failed and one eye (or rarely both) have not developed the neural connections from the eye to the brain due to disruption to the visual system such as
-stimulus deprivation amblyopia: where something e.g. tumor, ptosis, corneal opacity, deprives the retina of any stimulus, therefore, the brain doesn’t receive any signals to emmetropise.
-Strabismic amblyopia: the result of manifest strabismus which causes the brain to suppress one eye and therefore doesn’t emmetropise.
-Anisometropic amblyopia: the result of a difference in refractive error between two eyes where one eye will have the visual advantage at all distances.
-ametropic amblyopia: the reult of a high degree of uncorrected bilateral refractive error
-Meridional ambylopia: the result of uncorreced astigmatism therefore the retina did not recieve a clear image.