What is Lazy Eye (Amblyopia)?


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Evidence Based - Facts Checked

This content is medically reviewed by Dr. Udbhav Dorwal and written by Dr. Sandhya Shenoy

Last Medical Review Date - 16th November 2020


Consider this scenario. You have had a healthy life without being on medications for a long time. You don’t have any eye issues as well. However, one fine day you decide to go for an eye check-up because there is a free camp.

The ophthalmologist shows you a chart from a distance and asks you to read it with one eye closed. With the first eye, you read it with ease, without any assistance, feeling proud of yourself. But when you close the first eye and try reading with the other eye, you can read it with blurred vision. You try your best, but you cannot read the last few lines of the chart.

The doctor then suggests a trial of glasses. He makes you wear a spectacle in which he places trial lenses. One by one, he keeps on changing the lenses, but no matter what, the clarity of vision in that eye is not as crisp as it is in the other eye. 

Trial Lens

He then performs a series of tests and checks the retina. After all the tests, the doctor concludes that there is no problems in the eye. There is no cataract or retina problem, but he suggests you to wear glasses. To your surprise, even after wearing the glasses, you are still not able to read clearly. On checking with the doctor, you get to know that it’s a lazy eye.

Now your mind is full of questions. What is a lazy eye? How did you get it? How can you fix the lazy eye? Will my children have it?

Let us see it one by one.

What is Lazy Eye?

Lazy eye refers to the eye’s condition where the eye cannot see things clearly even with the best possible vision correction. In short, the eye is lazy to do its work.

This often happens due to uncorrected faulty vision in the eye in childhood. Most of the time, only one eye is affected, but in some cases, this condition can develop in both eyes. 

The earlier it is diagnosed and treated, the higher are the chances of full visual recovery. If not treated, this condition can cause permanent subnormal vision, and the patient will be literally one-eyed.

In the lazy eye medical condition, an individual may experience contrast sensitivity and depth perception issues along with visual clarity problem1Birch, E. E. (2013, March). 'Amblyopia and binocular vision' Source.

Let us See How’s an Object Visibility with a Lazy Eye? 

The light from any object passes through the eye’s structures to focus on the fovea centralis located in the retina. The structures through which the light passes are the cornea, anterior chamber, lens, vitreous and then fovea centralis.

In the retina, electrical impulses are generated, which travel to the brain via the optic nerve. These impulses strongly stimulate the visual centers in the brain where it is deciphered. That is how we come to know what object we are seeing.

In the lazy eye, the problem lies in the deciphering area of the brain. The brain chooses to suppress or ignore the weak impulses coming from the poor eye because they are not strong enough to stimulate the brain centers.

How's Dominance Characteristic of Eyes and Lazy Eye Related?

Like how we are either right-handed or left-handed (one side of our body is always dominant over the other); similarly, dominance exists in the eyes too2CV;, C. D. (2013). 'Looking at eye dominance from a different angle: Is sighting strength related to hand preference? Source

One eye is usually dominant over the other eye. But if the other eye's vision is better, both eyes balance themselves; however, little dominance always remains.

When the electrical impulses from only one eye are strong enough to stimulate the brain, the weaker impulses coming from the poor eye, which fails to stimulate the brain, are suppressed or ignored. This gives rise to a lazy eye, which is also called as Amblyopia.

How is Lazy Eye Condition Caused?

You must have had this in your childhood itself but you didn’t notice it because of the following reasons:-

  • One eye was doing the job of both the eyes.
  • You must have thought that the eyesight is normal.
  • You hadn’t checked the vision with one eye closed.
  • You hadn’t gone for a regular eye examination then.
  • Let’s Understand Lazy Eye’s Life Cycle Precisely right From childhood 

    Infographic Lazy Eye

    Kids can grow in any environment they are put into. That is because they have no previous experience with which they can compare themselves to.

    The connections between the brain and the eye develop during the first 8 -10 years of life. Anything that blurs the vision in one or both eyes can slow down or prevent the formation of these connections.

    So during those formative years, whatever impulses the brain gets from the eyes will determine the brain’s neural connections.

    If the brain is used to blurred impulses from one eye, right from the beginning, it will start thinking that it is normal for that eye because it has nothing to compare with (no prior experience registered in the brain). In this case, when the brain is already getting stronger and better impulses from the other eye, the brain will start ignoring the weak eye’s weak impulses and hence lead to lazy eye condition.

    What Are the Medical Conditions that Causes Blurring of Vision that Leads to Lazy Eye?

    Any condition in the eye, which causes blurring of vision or blocks the vision in that eye, causes lazy eye. The most common conditions are as follows:

    - Refractive Errors

    If the child has blurred vision in one eye due to near-sightedness or far-sightedness, or astigmatism, then the vision from that eye is blocked by the brain3TR;, B. B. (2013). 'The relationship between anisometropia and amblyopia' Source.

    - Cataracts

    Some children are born with cataracts due to some genetic diseases. The cataract can block the entry of light itself inside the eye and cause lazy eye, if not treated well on time4Louison S;Blanc J;Pallot C;Alassane S;Praudel A;Bron AM;Creuzot-Garcher C;. (2019). 'Visual outcomes and complications of congenital cataract surgery' Source.

    - Droopy Eyelid or Ptosis

    Not all cases of ptosis cause lazy eye. If the droopy eyelids are present since birth and are left untreated. In that case, the child can develop a lazy eye because the eyelids cannot open fully due to nerve issues and cover the pupils blocking the entry of light in the eye5Wang Y;Xu Y;Liu X;Lou L;Ye J;. (2018). 'Amblyopia, Strabismus and Refractive Errors in Congenital Ptosis: A systematic review and meta-analysis' Source.

    - Cross Eye or Squint

    In this medical condition, the alignment of both eyes is in different directions. One eye (the dominant eye) may be aligned straight, while the other eye can be in any other direction. Hence two images will be formed in the brain, leading to double vision. The brain will suppress the vision in one eye to maintain a single vision6J;, A. N. (2019). 'Eye Conditions in Infants and Children: Amblyopia and Strabismus' Source.

    - Diseases of the Cornea

    Cornea is generally transparent. Any disease or injury of the cornea can cause scarring like herpes simplex7MI;, B. (2019). 'Case Series: Pediatric Herpes Simplex Keratitis' Source and cause opacity thus preventing the light from entering inside the eye. If untreated, can lead to lazy eye8K;, P. E. (2018). A five-year retrospective study of the epidemiological characteristics and visual outcomes of pediatric ocular trauma' Source.

    - Glaucoma

    In some rare cases where the eye structures are not formed properly, there can be an increase in the ocular pressure (pressure in eyes) during birth. This can cause blurring of vision, and hence the visual impulses coming from this eye are ignored and hence result in the lazy eye9H;, S. (2011). 'Visual development and amblyopia prophylaxis in pediatric glaucoma' Source.

    - Tumor in Eye

    Tumors like retinoblastoma is known to occur only in childhood. If a child undergoes treatment for retinoblastoma there are chances, lazy eye condition may still develop due to the diseased state of that eye10CL;, P. R. (2020). 'Benefit of Patching Therapy to Minimize Amblyopia After Retinoblastoma Treatment' Source.

    When is the Right Age to Fix Lazy Eye?

    It is in childhood; the treatment has to start. Once the condition causing the blurred vision is rectified; the brain starts receiving clearer impulses from the lazy eye.

    As a result, the brain realizes that it is getting better vision, thereby leading to the correction of the lazy eye.

    However, this correction of the lazy eye doesn’t happen in adults. If the lazy eye is diagnosed later in life, the brain that has already grown up thinking that the lazy eye has to be ignored will resist the changes or the treatment11LB;, V. A. (2016). 'Amblyopia update: New treatments' Source, 12D;, D. (2014). 'Amblyopia' Source.



    Will My Child Suffer from Lazy Eye Condition?

    This condition can happen with or without a family history. The following are the different conditions that may result in a lazy eye.

    - If the child was born before time/ premature. Prematurity has its own sets of eye complications like retinopathy of prematurity (ROP). ROP is also known to cause lazy eye13Hennein L;Koo E;Robbins J;de Alba Campomanes AG;. (2019). 'Amblyopia Risk Factors in Premature Children in the First 3 Years of Life' Source.

    - Low weight at the time of birth14A;, B. P. (1991). 'Ocular defects in infants of extremely low birth weight and low gestational age'. Source

    - If anyone in the family has the similar condition15Guimaraes S;Vieira M;Queirós T;Soares A;Costa P;Silva E;. (2017). 'New pediatric risk factors for amblyopia: Strabismic versus refractive'. Source

    - If the child has other developmental disorders

    How Early Can We Diagnose Lazy Eye?

    The condition can be diagnosed as early as three months of age, where the infant can look at the light shown and follow the light wherever it goes.

    The present standard guidelines state that all children should be checked by an ophthalmologist at least four times before they turn 5 years old16Atowa, U. C., Wajuihian, S. O., & Hansraj, R. (2019, July 18). A review of paediatric vision screening protocols and guidelines. Source.

    Further, if anybody in the family has squint or cataracts or any eye diseases, the eye examination must be done even earlier.

    The appropriate age to get an eye check-up for your child to detect lazy eye medical condition well on time is as follows:-

    • Before the child turns three months old
    • In between the six months and one year of age
    • When your child turns three
    • When your child turns five years old

    However, the pediatrician usually checks for these during your regular visits and will direct you to the ophthalmologist if required.

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    How is it Diagnosed?

    A pediatric ophthalmologist diagnoses lazy eye by doing a series of age-appropriate tests.

    Diagnosis in Children Older than 5 Years

    The ophthalmologist will ask the child to read the numbers or the alphabets or recognize pictures in the chart and after that will do a glass check to see if the vision improves.

    If the vision improves, it means that the child needs a small correction in the vision for which glasses will be prescribed and the possibility of lazy eye is ruled out.

    However, while doing the glass check, if the vision doesn’t improve as much as the other eye, then the ophthalmologist shall recommend treating the lazy eye.

    Diagnosis in Children Younger than 5 Years

    In babies, the ophthalmologist will first show the light and check if the baby sees the light and follows the light when moved. In this test, both the eyes of the baby are kept open.

    In the second test, the ophthalmologist will check with one eye (of the baby) closed and see how the child behaves. If the child follows the light with one eye closed, it indicates that the open eye is normal; however, if the child tries to push away the thing blocking the closed eye, it suggests that the open eye has a blurring vision.

    The ophthalmologist may also perform a retina check by putting eye drops and seeing any condition in the eye causing blurring of vision like cross-eye or drooping eyelids, cataracts, refractive errors, etc.

    What Are The Symptoms of Lazy Eye?

    Following are the symptoms of lazy eye17Blair, K. (2020, August 10). 'Amblyopia' Source:-

    - Cross eye or squint

    - A child going closer to the object of interest because of the lack of ability to focus on it from a distance

    - Difficulty in catching and throwing objects

    - Improper depth perception

    - Head tilting

    - Complaints of objects being blurry

    How Can I Prevent Lazy Eye?

    Following are some of the ways to prevent lazy eye:-

    - Routine Eye Examination

    The best way to prevent it is by subjecting your child to routine eye examinations as early as possible. This condition develops due to uncorrected refractive error in childhood. Hence if required, the treatment should start as soon as it is diagnosed.

    - Blurred Vision Should be Taken Seriously

    Any complaints of blurring of vision by your child shouldn’t be taken lightly. A thorough evaluation shall be required to determine the reason for the blurred vision and thereby follow the visual correction prescribed by your ophthalmologist to prevent lazy eye medical condition.

    - Diet

    The child should be given a diet that is rich in vitamin A and E.

    - Self Checkup

    A simple routine home check-up of each eye’s vision (with the one eye closed) can help in the early diagnosis of the reason for blurriness and thereby, if treated well on time, can prevent lazy eye.

    - Quit Alcohol and Smoking

    There is an entity called as toxic amblyopia. This happens due to increased consumption of alcohol18SA;, P. (1988). 'Alcohol amblyopia' Source and tobacco19A;, G. (2005). 'The development of research on the effect of tobacco consumption on the visual organ over the last 200 years' Source. This can be prevented by reducing or quitting alcohol and tobacco.

    Why Is It Important to Treat Lazy Eye?

    - Permanent Loss of Vision

    Lazy eye, if not treated, can cause permanent visual loss20 Blair, K. (2020, August 10). 'Amblyopia' Source

    - Poor Vision

    In the later part of the life, if the child cannot use to his/her good eye because of any disease or injury, he or she will have to depend upon the poor vision of the lazy eye. Therefore, it would be better if the lazy eye is treated as early as possible.

    - Behavioral Issues in Children

    Sometimes, uncorrected refractive errors and lazy eye in small kids can cause behavioral issues that may look like developmental disorders but in reality, the problem is purely visual. In a small population of cases, the kids with lazy eye can develop problems in fine motor skills21 B;, W. A. (2008). 'The effect of amblyopia on fine motor skills in children' Source.



    References

    1. 1
      Birch, E. E. (2013, March).
      Amblyopia and binocular vision.
      Retrieved November 15, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3577063/
    2. 2
      CV;, C. D. (2013).
      Looking at eye dominance from a different angle: Is sighting strength related to hand preference?
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/23357202/
    3. 3
      LB;, V. A. (2016).
      Amblyopia update: New treatments.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/27152486/
    4. 4
      D;, D. (2014).
      Amblyopia.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/24852148/
    5. 5
      TR;, B. B. (2013).
      The relationship between anisometropia and amblyopia.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/23773832/
    6. 6
      Louison S;Blanc J;Pallot C;Alassane S;Praudel A;Bron AM;Creuzot-Garcher C;. (2019).
      Visual outcomes and complications of congenital cataract surgery.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/30898370/
    7. 7
      Wang Y;Xu Y;Liu X;Lou L;Ye J;. (2018).
      Amblyopia, Strabismus and Refractive Errors in Congenital Ptosis: A systematic review and meta-analysis. 
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/29844360/
    8. 8
      J;, A. N. (2019).
      Eye Conditions in Infants and Children: Amblyopia and Strabismus.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/31454213/
    9. 9
      MI;, B. (2019).
      Case Series: Pediatric Herpes Simplex Keratitis.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/30801497/
    10. 10
      K;, P. E. (2018).
      A five-year retrospective study of the epidemiological characteristics and visual outcomes of pediatric ocular trauma.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/29347941/
    11. 11
      H;, S. (2011).
      Visual development and amblyopia prophylaxis in pediatric glaucoma.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/21725660/
    12. 12
      CL;, P. R. (2020).
      Benefit of Patching Therapy to Minimize Amblyopia After Retinoblastoma Treatment.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/32507274/
    13. 13
      Hennein L;Koo E;Robbins J;de Alba Campomanes AG;. (2019).
      Amblyopia Risk Factors in Premature Children in the First 3 Years of Life.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/30889262/
    14. 14
      A;, B. P. (1991).
      Ocular defects in infants of extremely low birth weight and low gestational age.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/1995049/
    15. 15
      Guimaraes S;Vieira M;Queirós T;Soares A;Costa P;Silva E;. (2017).
      New pediatric risk factors for amblyopia: Strabismic versus refractive.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/28967080/
    16. 16
      Atowa, U. C., Wajuihian, S. O., & Hansraj, R. (2019, July 18).
      A review of paediatric vision screening protocols and guidelines.
      Retrieved November 15, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6629797/
    17. 17
      Blair, K. (2020, August 10).
      Amblyopia.
      Retrieved November 15, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK430890/
    18. 18
      SA;, P. (1988).
      Alcohol amblyopia.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/3397491/
    19. 19
      A;, G. (2005).
      The development of research on the effect of tobacco consumption on the visual organ over the last 200 years.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/16521981/
    20. 20
      B;, W. A. (2008).
      The effect of amblyopia on fine motor skills in children.
      Retrieved November 15, 2020, from https://pubmed.ncbi.nlm.nih.gov/18235004/

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