Amblyopia, Sign and Symptoms, Causes, and Treatment

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What is Amblyopia or Lazy Eye?

Amblyopia is a vision deficit state, where vision loss occurs in one or both of the eyes even after Glass or contact lens prescription by an Optometrists. The term Amblyopia is also known as the “Lazy eye state“. The vision loss can be partial in most cases of Amblyopia. Amblyopia is diagnosed in early childhood or in infants. One eye or both of the eyes are affected by amblyopia resulting in reduced visual acuity. The most critical time for a child to suffer from amblyopia is below the age of 6.

 

Amblyopia is produced by certain factors that lead to visual disorder. If detected at an early age, it can be treated with the visual correction Aid or curing the disease that is causing the vision deprivation.

American Academy of Ophthalmology (AAO) denotes amblyopia as:

A two eyes vision difference is about 2 lines or more than 2 lines in a visual acuity table (without specifying any), or visual acuity equal to or worse than 6/9 with the best optical correction.

 

In research conducted in Nepal Eye hospital from June 2006 to 2011, it was found, the prevalence of amblyopia is 0.7% in schooling children.

Amblyopia is pronounced as am·blee·ow·pee·uh. 

 

Amblyopia Medical Definition

As per medicine.net, the medical definition of Amblyopia is

“Partial or complete loss of vision in one eye caused by conditions that affect the normal development of vision. These conditions include strabismus, in which the eyes are crossed inward (esotropia) or turned outward (exotropia) and anisometropia, in which there is a major difference in refractive error between the two eyes from nearsightedness, farsightedness, or astigmatism. Less common causes of amblyopia include ptosis (drooping) of one eyelid, disease of the cornea (preventing light from entering the eye), congenital cataract, and injury to the eye of a young child.”

 

Signs and symptoms of Amblyopia

The symptoms of amblyopia are usually not noticeable but some parents can notice the diversion of the eyeball in their children. The diversion is also known as “Strabismus” or “ Squint”. If you ever see your child looking with a nodded head, or misalignment of the eye, it is the best time to go see an Ophthalmologist or an optometrist at the nearest eye care centres. Children have blurred vision but they can’t able to tell at a small age.

 

How parents can know the child has a lazy eye or not?

Parents can determine if their child has amblyopia. All you got to do is cover a single eye while he/she is watching tv or doing any kinds of stuff and repeat the similar to the other eye. If your child is bothered while you cover the eye, it means he/she has blurred vision in one of the eyes. You probably have covered the good eye which means the other eye cant see properly.

But a simple test doesn’t define the state of the eye, you have to take your child to an eye care practitioners. 

 

What Ophthalmologists find while examining?

The pediatric ophthalmologist will find the following observation during the examination of your child.

  • The recognition of visual acuity is more affected than resolution acuity.
  • Eye squinting and lids are half-closed to see better.
  • Visual acuity is less than normal 6/6 when tested with different vision charts.

What causes amblyopia?

Based on the common types of amblyopia, here are the causes.

Strabismic Amblyopia

Prolonged squinting of an eye in child results in uniocular suppression. The brain ignores the visual stimuli from the squinting eye to maintain a clear vision of the other eye and prevent diplopia.

Refractive Amblyopia

It includes three major cases. It is caused by the refractive error in the eye. A child can have different refractive status in both eyes. That can be either, Anisometropia, Isometropia or Astigmatism even after perfect alignment of the two eyes.

Stimulation Deprivation

This happens when something impedes the light to reach the retina. Congenital and traumatic cataracts, Corneal opacity, ptosis covering the pupil are the major cause of stimulation deprivation.

Simplifying the above cause the main cause of amblyopia is due to the squinting eye, having a refractive error in one or both eyes which need optical correction, or the disease that blocks the light to reach to Retina (Due to Cataract, Opacity, Lid disease specially Ptosis).

Note: Longhairs or fringe/ bangs doesn’t cause amblyopia unless the bangs are thick and obstruct light continuously to reach the eye.

Girl with bangs that don't cause amblyopia
Girl with bangs that don’t cause amblyopia

How to Correct Amblyopia or Lazy Eyes?

Treatment

The treatment for amblyopia should be started as early as possible, a younger child has a better prognosis. Prevention is always better than cure so that earlier eye examination of child may prevent amblyopia.

The American Optometric Association recommends

“That all children have their first eye exam at 6 months of age, another exam at age 3 and a third exam prior to entering school to ensure the vision is developing normally in both eyes and there is no risk of amblyopia”

 

Treatment of amblyopia will be done according to the cause

In refractive error induced amblyopia, it is necessary to correct the errors with glasses or contact lens. If only one eye has more refractive error than others (Anisometropia) However the patching of the good eye is a must. It is done to force the brain to pay attention to the stimuli of the amblyopic eye.

The glass will make a clear vision in case of refractive error.
The glass will make a clear vision in case of refractive error.

Treatment of strabismic amblyopia involves surgery to straighten the squinting eye that is followed by Patching in the good eye. Some orthoptics aid could help both eyes work mutually also known as Vision therapy.

The prosthetic contact lens can be an option if your child throws away the patch. But prosthetic contact lenses are costly and it needs contact lens examination and proper care of the eye.

Atropine eye drops can also be a substitute for the patch. Atropine eye drops cause blur vision in one eye, forcing the other eye to work. It doesn’t require proper care of your child to notice if he/she is wearing the patch or not. But the atropine has its own side effects. Light sensitivity and paralysis of ciliary muscle due to long term use. Do not use Atropine Eye Drop without Doctor’s Prescription.

Any opacity in visual media-induced amblyopia like cataracts should be operated and opacified lenses should be removed. Changing of the cornea by surgery (Keratoplasty) for dense corneal opacity. The blue and opacified cornea of the recipient is changed by a clear donor cornea. If the child has ptosis (dropping of the lid) it may correct surgically or using Ptosis Crutch Glass suggested by Pediatric Ophthalmologist or Oculoplasty Surgeon.

 

How is patching done?

kids with amblyopia and patching done
Kids with lazy eye using patching therapy.

Patching is done in the ratio of the age of the child to the Amblyopic Eye. An ophthalmologist will suggest the best option of treatment. Example: If a child is 3 years of age, patching is done in the ratio of 3:1 i.e  3 days in the sound eye and one day in the normal eye.

Note: The amblyopic eye is also patched so as to prevent amblyopia in the good eye due to regular patching of the good eye.

Duration and Start of patching therapy

Patching should be done as sooner as possible. It may last as long as the vision is not fully restored or the visual improvement doesn’t occur even after strictly practised patching for 3 months from the start.

 

Where to Buy Eye Patch in Nepal?

Many major eye hospitals of Nepal advise buying specially made orthoptic eye patches for occlusion therapy available at their pharmacy or the optical shop, but some hospital and clinics ask their patients to make eye patch using tape and bandage (Cheaper method) which sometimes cause allergies to the skin of the child and it’s difficult to maintain hygiene may cause eye infections also (Pink Eye).

Key features of good lazy eye patching tape

  • Gentle Adhesive to Skin
  • Sticks well and remove easily so the child will not hurt while removing
  • Highly Breathable (Best for  children’s skin
  • Hypoallergic material
  • Latex-free material
  • 5*7.5 cm size (commonly available)

Please look for an adhesive eye patch that came with every single sterile packaging, which is the most important requirement to maintain ocular hygiene. You can find it easily at the nearest eye hospitals if you don’t find this in your nearest eye care service providers you can buy it online from Daraz online shopping.

How to treat amblyopia in adults?

To treat amblyopia in adult, it needs to rule out the causes of amblyopia and the effects on visual acuity and other visual parameters of the patients. Based on that optometrist and Ophthalmologist will suggest advice or tell about the prognosis of the amblyopic eye.

 References and notes:

  • Atropine an effective alternative to patching for amblyopia.
  • Review of Ophthalmology. October 2003.
  • Https://www.ncbi.nlm.nih.gov/pubmed/23584645

If you are from Nepal, Watch this video related to amblyopia (Lazy Eye) in the Nepali Language. Watch the video of Lazy Eye.

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