Lazy Eye

Useful Terms

Amblyopic = the eye with poorer vision when one eye has good vision and the other does not; usually, only one eye is amblyopic; affects 2 – 3 out of every 100 people

Bilateral amblyopia = both eyes are “lazy” and have poor vision

Refraction = a visual image is formed through the focusing of light onto the retina

Refractive amblyopia = both eyes experience different amounts of the improper focusing of light

Common Symptoms

  • Poor vision in one eye
  • Generally poor overall vision
  • Resorting to squinting, tilting one’s head to the side, or closing an eye to see better
  • Dreadful depth perception (characterized by an ability to judge the relative distance between objects)
  • Inward or outward-wandering eye
  • Headaches

Risk Factors

  • Having misaligned eyes due to strabismus (either one of the eyes turns all of the time in one direction)
  • Significant near- or farsightedness in both eyes
  • Unequal amount of vision in both eyes (one eye may be more near- or farsighted than the other)
  • Having a cataract, droopy eyelid, or any other condition that prevents light from focusing and entering into the eye properly
  • Hereditary = medical history of amblyopia or strabismus in the family
  • Premature birth
  • Low birth weight

Causes

  • Mainly caused due to the hereditary risk factor
  • Can be caused by any condition that impairs normal use of the eyes and ongoing vision development
  • May usually be detected in early childhood
  • There are 3 main causes:

    • Strabismus

      • Most common cause of amblyopia
      • The misaligned / crossed / turned eye will be turned off so as to avoid double vision
      • This leads to the child using the eye with better vision exclusively
      • The misaligned / crossed / turned eye will have no visual development, thus failing to improve vision
    • Unequal Focusing of Light = Refractive Errors

      • If and when an eye is out of focus or blurred, it will “turn off” and develop amblyopia.
      • Amblyopia becomes difficult to detect because even though one eye has poor vision, both eyes will appear to have normal vision when they are open
      • This unequal focusing of light may be a symptom of another eye condition, such as nearsightedness, farsightedness, or astigmatism
      • If any of these conditions co-occur with amblyopia and are of a high degree, then amblyopia can occur in both the eyes, which will then encounter very blurred vision
    • Cloudiness in the Eye Tissues

      • Cataracts may lead to amblyopia
      • A cataract is characterized by a cloudiness in the naturally clear lens of the eye
      • This will prevent the focusing of clear images on the retina in the back of the eye, which directly leads to the development of amblyopia
      • This is usually the most dangerous form of amblyopia that can be developed
         

Diagnosis

  • Amblyopia is usually found by discovering a difference in the vision that the two eyes experience, whether it’s a situation of good vision in one and poor vision in the other or poor vision in both eyes.
  • The ophthalmologist will look for visual sensitivity by covering one eye up with a patch and observing how the child will use the other eye to follow or look at objects
  • Furthermore, the doctor will be able to test for the condition through the reaction of the child when an eye is covered

    • If the strong eye is the one covered with the patch and the eye being used is amblyopic, then the child will try to:

      • 1) Look around the patch
      • 2) Try to pull it off, or
      • 3) Cry
  • It is important to note that poor vision in one eye doesn’t always translate to amblyopia.
  • The doctor will also look for the presence of other eye conditions by examining the insides of the eyes for:

    • 1) Cataracts
    • 2) Inflammations and/or swelling
    • 3) Tumors, or
    • 4) Other problems within the eye

Treatment

  • Treatment needs to commence as soon as possible to allow visual development to occur properly
  • Lack of Treatment may lead to:

    • 1) The development of a significant and permanent visual weakness in the amblyopic eye
    • 2) Without good vision in both of the eyes, depth perception could be lost
    • 3) If the stronger eye is injured or contracts or disease, then the patient will forever have dreadful vision in both eyes
  • Lazy Eye Patching (Obscuring)

    • In the case of the occurrence of refractive amblyopia, eyeglasses may initially be prescribed as a way of correcting the focusing errors.
    • If the glasses by themselves are insufficient in improving the child’s vision, then the strong eye will be patched for a period lasting anywhere from weeks to months.

      • The patch forces the child to use the weaker, amblyopic eye to strengthen and mature its good vision
      • Patching can also be substituted with:

        • 1) Special eyedrops to blur the vision in the strong eye, or
        • 2) Prescribing eyeglasses with a blurry lens that covers the strong eye
      • It is necessary to maintain the patching on a part-time basis for several more years, even after the weaker eye has regained its vision in order to preserve the improvement
  • Surgery

    • If the ophthalmologist finds another eye condition, such as cataracts or the others aforementioned, that causes the poor vision, then surgery could be required to fix the problem that is causing amblyopia
    • It will be treated before surgery to correct any misaligned / crossed / turned eyes and after surgery with the continuation of the patching process
    • Even if surgery corrects the cause of the condition, the condition still needs to be treated to reverse the damage it has done
  • Successful treatment depends on the severity of the condition and the age of the child when treatment begins

    • Vision can improve for most children if the condition is found and treated early on
    • Within those cases that the condition is caused by strabismus or refractive errors, amblyopia can be successfully treated within the first 9 years of the child’s life and will never reoccur
    • When the cause is the cloudiness in the eye tissues, the issue needs to be found and treated very early within the first few months of life for successful treatment
    • Amblyopia that is not detected until after early childhood may not be successfully treated