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Why Does Amblyopia Happen?

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How does amblyopia occur?
Photo: https://www.drstephenchase.com/

Sight is arguably the most important sense and it affects our everyday life. It is not surprising that it is also one of the most complicated systems in our bodies. As with any other complex system – there are numerous elements that must work in complete sync. When one eye is not in sync and is sending worse signals to the brain, we are talking about amblyopia (or lazy eye).

Amblyopia Explained

Amblyopia is a condition characterized by reduced vision in one or both eyes that is not caused by any structural abnormalities in the eye itself. Instead, the problem lies in how the brain processes visual information from the affected eye. When the brain receives blurry or conflicting images from the eyes during early childhood, it suppresses or ignores the input from the weaker eye to avoid confusion. As a result, the underused eye fails to develop properly, leading to reduced visual acuity or amblyopia.

Prevalence of Amblyopia

It is oftentimes surprising that lazy eye or amblyopia is quite unknown in the general population. While it may sound like quite a niche problem, there are more than 200,000 cases in the US every year. Some studies show that about 2% of the population are suffering from serious lazy eye, while some indicate this goes as high as 5% for some forms of amblyopia. Amblyopia is also one of the most common visual dysfunctions of children.

What Causes Amblyopia? | Types of Amblyopia

Although we might simplify that amblyopia is an inability of the eye to focus clearly, it is much more than that. The National Eye Institute describes several causes that result in the development of a lazy eye:

  • Refractive Error: Refractive error (observed as blurry vision) is oftentimes referred to as either nearsightedness, farsightedness or astigmatism. It is a result of the eye’s inability to focus light on the retina. Refractive amblyopia develops as a consequence of refractive error. Because the eye with the refractive error sends a blurry image to the brain, the brain starts disregarding that image. Because the eye is underutilized, it starts becoming weaker and starts developing refractive amblyopia.
  • Strabismus: The most frequent type of amblyopia is strabismic amblyopia, which is a result of misaligned eyes. Because the images that each eye is sending to the brain are not aligned, the brain has a hard time combining both images.
  • Cataract: Lazy eye caused by cataract is called deprivation amblyopia. A cataract causes the blurry image in the front part of the eye, which prevents light from entering and focusing in the eye.

Development of Amblyopia: Importance of Critical Period

The critical period for visual development occurs during infancy and early childhood, typically up to the age of eight. During this period, the brain’s visual pathways undergo substantial growth and organization. Any disruption in this process can lead to amblyopia. The development of amblyopia typically follows these stages:

  1. Suppression: When the brain receives disparate visual input from both eyes, it resorts to suppressing the weaker eye’s images to avoid confusion. As a result, the neural connections responsible for processing visual information from the suppressed eye weaken over time.
  2. Loss of Visual Acuity: Over an extended period, the underused eye experiences a decline in visual acuity, making it difficult to perceive fine details and reducing its ability to see clearly.
  3. Perceptual Dominance: The brain begins to rely solely on the stronger eye for visual information, leading to the dominance of one eye over the other. Even if the vision in the weaker eye is improved later, the brain may struggle to integrate its input effectively.

Amblyopia Diagnosis

However, there are indications of how we can notice that there might be something amiss in our child’s vision. One of them is that we might notice the drift of one eye, which may appear as misaligned.

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The other way is to see how a child reacts when they have one eye closed. If they complain about having a blurry image, they might be suffering from a lazy eye.

In any case, you should schedule an eye exam with the eye doctor specialized in pediatric eye care.

We prepared a short blog post that takes you through a basic procedure on how you can test a little bit if there are any discrepancies. You can check the steps here, however, this does not, in any case, replace the need for a vision exam by a trained professional!

There are several ways how one can start treating amblyopia and we’ve prepared a very informative blog that talks about active treatment options for you, through which we are able to rebuild the vision that was previously lost to lazy eye.

Frequently Asked Questions

What is the critical period for the development of amblyopia?

The critical period for visual development occurs during infancy and early childhood, up to around the age of eight. During this time, disruptions in the growth and organization of the brain’s visual pathways can result in amblyopia. The stages include suppression, loss of visual acuity, and perceptual dominance, making early detection and intervention crucial.

How can amblyopia be diagnosed, and what signs should parents look for in their children?

Signs of amblyopia may include the drift or misalignment of one eye. Parents can also observe a child’s reaction when one eye is closed; complaints about blurry vision may indicate a lazy eye. However, a conclusive diagnosis requires a professional eye exam by a pediatric eye care specialist.

How can parents test for potential vision issues in their children at home?

While there are basic procedures parents can follow at home to test for discrepancies, such as observing eye drift or closure reactions, these are not substitutes for professional eye exams. It is recommended to schedule an eye exam with a trained specialist for accurate diagnosis and treatment.

Is there a recommended age for initiating treatment for amblyopia?

Early intervention is crucial. The critical period for visual development is during infancy and early childhood. Detecting and addressing amblyopia at this stage increases the likelihood of successful treatment and vision improvement.

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Based on the data from over 15,000 patients using AmblyoPlay, improvements start within 4 months, while optimal results take anywhere between 6-18 months on average. The duration of required training depends on the patient’s age, the severity of the problem, accompanying diseases, and adherence to the training program.