Amblyopia: An In-Depth Exploration

What Is Amblyopia?

Amblyopia, commonly known as “lazy eye,” is a visual disorder that results in reduced vision. It typically develops during childhood and can lead to permanent vision problems if left untreated. Let’s explore the causes, symptoms, risk factors, and treatment options for this condition.

Causes of Amblyopia

 Amblyopia usually begins in childhood because as children are developing, their eyes and brain are learning how to communicate with each other and interpret visual information. If a child has sharp enough vision with both eyes working together, their eyes and brain learn how to see clearly in both eyes. If they have significantly blurry vision or both eyes do not work together, their eyes and brain learn how to see blurry in the neglected eye or eyes.

Basically, everything is healthy with an amblyopic patient’s eyes and brain, but their brain has learned only how to interpret vision as blurry. If a child’s amblyopia is treated in time, their brain can still slowly learn how to interpret vision as clear. If amblyopia is not treated in time, their brain will be unable to learn how to see clearly and the condition will be permanent. No glasses, contact lenses, nor surgery will fully sharpen an amblyopic eye’s vision once it is permanent. Now, let’s delve deeper into the actual causes of amblyopia.
 

•  Muscle Imbalance (Strabismic Amblyopia): Strabismus describes the condition when the eyes are not working together. Usually, an imbalance in the eye muscles causes the eyes to not look at the same target. This imbalance can be caused for many reasons. Muscles in one eye may be weaker than the muscles in the other eye, muscles may be shorter in one eye causing them to pull on one eye more than the other, the nerves in one eye’s muscles may be more sensitive than the other eye, etc. For whatever the reason, one eye looks at the target while the other eye points inward (cross-eyed), outward, up, or down. This causes the brain to see two images (double vision), and the brain does not like double vision. To prevent double vision, the brain ignores or suppresses the eye that is pointing away from the target resulting in one image (single vision). Since the brain ignores one eye, it never learns how to see clearly through that eye. If it did, the double vision would occur again. This condition can easily be fully corrected or avoided all together if it is treated in time.

• Difference in Sharpness of Vision (Refractive Amblyopia): Refractive error (farsightedness, nearsightedness, and astigmatism) is basically a person’s glasses prescription. There are two types of refractive amblyopia, isometropic amblyopia and anisometropic amblyopia. Isometropic amblyopia occurs when a child’s prescription is so high in both eyes that the brain cannot learn how to see clearly in either eye. This can easily be avoided/treated if a child receives a correct glasses prescription early enough. Some children have very different prescriptions in each eye. If the prescriptions are so different that one eye sees very blurry, it can cause issues like glare and blurry vision with both eyes open when the brain tries to piece the two images from each eye together. To solve these issues, the brain again suppresses the affected eye and never learns how to see clearly through it. This is called anisometropic amblyopia and is one of the hardest conditions for parents to discover because the child has one good eye and both eyes usually point in the same direction. The child also usually thinks that their vision is normal because they do not know better as they have lived with this all their life. Luckily, this condition also can easily be fully corrected or avoided all together if it is treated in time.

• Deprivation Amblyopia: This rare condition occurs when something physically blocks the eye from seeing. Common causes of deprivation are congenital cataracts, eyelid ptosis, and ocular growths. Congenital cataracts are a clouding of the lens inside the eye present at birth. If the lens is cloudy enough, it will block enough vision to cause amblyopia. Eyelid ptosis is a droopy eyelid. If the eyelid droops so much that it blocks light from entering the eye, it can lead to amblyopia. If anything grows in or on the eye, such as a tumor or a limbal dermoid, that it blocks light from entering the eye, it can also lead to amblyopia. Deprivation amblyopia in general can quickly cause very blurry vision because mostly all vision is blocked in the affected eye. Luckily, this condition is rare, but urgent treatment is necessary to prevent permanent vision loss.

Symptoms and Signs

As there are many different types of amblyopia, there are many different symptoms and signs. An observant parent may be able to identify some of these symptoms on their own and bring their child to an eye doctor for treatment. However, even the most observant person may not be able to catch amblyopia without performing an eye exam because symptoms may be so subtle or non-existent. The following are some signs to look out for:

• Blur: The amblyopic eye must be blurry for it to be diagnosable as amblyopia. Because the eye is so blurry, children tend to favor the non-affected or less affected eye.

• Wandering Eye: The affected eye may look in a different direction than the non- affected eye. Since amblyopia mainly affects one eye, the affected eye may turn in, out, up, down, or a combination of these.

• Poor Depth Perception: Amblyopic patients may have difficulty in judging distances accurately. True depth perception needs sharp vision from both eyes working together. When a patient suppresses an eye, they functionally are only using one eye. This provides basic depth perception like being able to tell that a ball is in front of a person because the ball blocks the view of the person, but it is almost impossible to judge how many feet away the ball and the person are (true depth perception). This can be detrimental to driving safety as well as sports where depth perception is essential. Patients with amblyopia in both eyes also have reduced depth perception due to blur even if their eyes work together.

• Squinting or Shutting an Eye: When children are young, they usually cannot fully suppress their affected eye yet. In one way, this is good because if they receive treatment soon, recovery will usually be very quick. However, the child does not know anything about the disease. All the child knows is that they see double and/or blurry when both eyes are open. They normally squint to make things sharper or shut the affected eye to prevent the blur from getting in the way of the non-affected eye.

• Head Tilting: A child may tilt his or her head to sharpen their vision. If a child has a strabismus, tilting their head may allow them to use both eyes together. For example, if one eye cannot turn to the right, the child might turn their head to the right instead. Now both eyes may be able to look at the same target together in this situation. Tilting their head may sharpen their vision as well. Head tilt can sometimes have the same effect as squinting to see better. A child may notice that they see better when they tilt their head and make a habit of this to see clearer more often.

• Abnormal Vision Screening Results: Amblyopia may not be evident without a comprehensive eye exam or a school screening. Humans in general are very adept at adapting to their situation. Many children just learn to live with amblyopia. They compensate for it so well that even a trained observer may not be able to tell a child has amblyopia by just looking at them. As children get older, they suppress their affected eye more and more, which decreases the more obvious symptoms and signs of amblyopia. However, by definition, amblyopia must have a reduction in vision. This is can easily be caught by a comprehensive eye exam or properly performed school screening.

Risk Factors

Several factors increase the risk of developing amblyopia:

• Premature Birth: Premature infants are more susceptible to amblyopia as well as other eye conditions.

• Small Size at Birth: Low birth weight may also contribute to amblyopia.

• Family History: A family history of lazy eye increases likelihood that a child may develop amblyopia.

  
  Early Intervention Matters

• Regular eye exams for children between ages 3 and 5 are essential. Eye exams even earlier would be even better if possible. The earlier amblyopia is found and diagnosed, the better the prognosis of full recovery. Ideally, an infants first eye exam should be around age 1.

• Prompt diagnosis and treatment significantly improve outcomes.
   

Treatment options include:

• Patching the Stronger Eye: Encourages the weaker eye to develop better vision.

• Corrective Lenses: Address refractive errors.

• Vision Therapy: Exercises to improve eye coordination.

• Surgery: For cases related to muscle imbalance as well as deprivation amblyopia.

Conclusion

Amblyopia is a complex condition, but with early intervention and proper management, children can achieve better vision. For more information on amblyopia, please visit iCare Optometry at our office in Idaho Falls, Idaho.

We work with our patients to understand their visual needs and help them in the best way possible. Please call (208) 522-2839 to discuss any questions with our team of experts or to schedule an appointment today.