If we want to understand the true cause of amblyopia and the most effective treatment then it is essential to understand the concept of binocular competition. What does that mean? To explain it in a simple and illustrative way, allow me to use another analogy. Imagine that the two eyes are twin brothers and their mother is in the visual cortex of the brain.
16. Mother and twins representing the brain and two eyes.
The brothers both want to talk to their mother. In a normal and well-functioning visual system, there is good communication between the three; sometimes one brother will speak while the other listens, and vice versa. When the brother work in this coordinated manner the mother has the easiest time receiving the information.
Let’s see how the normal process of binocular competition gets distorted, thus producing an amblyopic eye. When the process gets distorted, the better seeing eye will behave like a bully and the amblyopic eye as the less assertive brother. Whenever the less assertive brother wants to talk to mom, the bully will cover the less assertive brother’s mouth preventing him from speaking to her.
17. The bully represents the good eye and the less assertive brother represents the amblyopic eye.
Over time the less assertive brother gets less and less assertive, so that eventually he loses the desire and ability to speak to the mother. After a while, the only one doing the talking is the bully. This process of abnormal binocular competition or bullying is called active suppression.
18. The “amblyopic eye” loses the desire to speak to the mother.
During treatment, if you want the less assertive brother to be able to communicate with mom, first you must put the bully in a different room so that the bully cannot cover his brother’s mouth he tries to speak.
19. The “bully” being sent to a different room to reduce the binocular competition.
This is effectively what happens when you put an eye patch on the good eye. What happens when the bully re-enters the room (i.e., when we remove the patch)? The bully will make use of its strength and superiority and will once again cover the mouth of his brother! This is why only patching is not the most effective treatment, and the gains made during patching are lost after the patch is removed.
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