專家教學

Amblyopia

Author: Vanessa Thai
Developmental and Behavioural Optometrist
Central Health Southside – Child Development Team

What Is It?

Amblyopia, often referred to as lazy eye, is a condition characterised by the reduced vision in one or both eyes, which cannot be corrected by glasses or contact lenses. It typically occurs in childhood and is most commonly associated with early childhood strabismus or significant differences in refractive errors between the two eyes.

Causes of Amblyopia

Amblyopia can develop from eye and vision conditions including:

Strabismus

When the eyes are misaligned, the brain may receive conflicting visual information from each eye, leading to the perception of double vision. To avoid double vision and confusion, the brain may suppress or ignore the input from the misaligned eye. This suppression can prevent the normal development of visual acuity and other visual functions in that eye, leading to amblyopia.

Refractive Error

When there is a significant difference in the refractive errors/prescriptions (e.g., one eye has much more shortsightedness, longsightedness, or astigmatism than the other), the brain may favour the eye with better focus, causing amblyopia in the weaker eye.

Deprivation

This type of amblyopia occurs when a structural problem, such as a congenital cataract (cloudiness of the crystalline lens in the eye) or a droopy eyelid, obstructs light from entering that eye, leading to amblyopia.

Signs and Symptoms

Amblyopia often develops without noticeable signs or symptoms. The eye with reduced vision may appear normal, and the condition may not cause discomfort. However, some potential indicators include:

  • Reduced visual acuity – the amblyopic eye often has poorer visual acuity, meaning it does not see as well as the other eye.
  • Closing one eye – children with amblyopia may squint or close one eye to try to see better.
  • Poor depth perception – amblyopia can lead to reduced depth perception and problems with judging distances accurately because the eyes are not performing equally.
  • Eyesight cannot be optimally corrected – despite using prescription spectacle glasses or contact lenses, the vision in the amblyopic eye does not improve.
Diagnosis

The diagnosis of amblyopia often begins with a comprehensive eye examination with an optometrist involving:

Comprehensive History

Children with a family history of strabismus, amblyopia, and other serious eye diseases are at higher risk.

Cover Test, Eye Tracking, and Visual Acuity

Since young children may not be able to provide subjective responses, an optometrist may observe the child’s reactions when one eye is covered, their eye movements, or how well they follow an object. If there is a difference in visual clarity between the eyes, the child may display behaviours such as attempting to look around the patch, pushing it away, or expressing distress when the stronger eye is covered. If there is misalignment, the uncovered eye may move to fixate on the object when the other eye is covered.

Refractive Assessment

Determining if significant differences in refractive errors exist between the two eyes.

Pupil Responses

Assessing how the pupils react to changes in lighting and focusing.

Full Ocular Health Exam

By checking the external and internal structures of the eyes, other eye problems that may interfere with normal vision development can be ruled out.

Treatment Options

Common approaches to managing amblyopia often involve penalising the stronger eye, which forces the brain to rely on the weaker one, in turn encouraging it to develop a stronger visual connection.

Patching or Atropine Drops

Also known as occlusion therapy, the stronger eye may be patched for a specific number of hours each day. Alternatively, atropine eye drops can be used to blur the vision in the stronger eye, allowing the amblyogenic eye to improve its visual acuity.

Vision Therapy

Vision therapy may be recommended to improve eye coordination and visual skills in children with amblyopia, especially when strabismus is present. Engaging in visual activities that stimulate the amblyopic eye, such as using specific games, VR technology, and exercises, can complement the treatment program.

Correction of Refractive Errors

If amblyopia is associated with a significant difference in refractive errors between the eyes, prescription spectacle glasses or contact lenses may be prescribed to maximise visual acuity in both eyes. Sometimes, glasses may be prescribed to blur the vision in the stronger eye.

Treatment of Underlying Causes

In cases of deprivation amblyopia due to structural issues like cataracts or ptosis (drooping eyelid), referrals to an ophthalmologist for surgical correction of the underlying problem may be necessary. Occlusion therapy may still be recommended after surgery to continue the engagement of the weaker eye.

Amblyopia or Strabismus, Lazy Eye or Squint?

Amblyopia (lazy eye) and strabismus (squint) are terms often confused by parents and caregivers because they often occur at the same time. A misaligned eye can be ignored by the brain causing it to be lazy. Both conditions can be caused by uncorrected refractive errors (high prescriptions) and eye problems such as congenital cataracts.

An important point to note is that they are distinct conditions – while a misaligned eye can be lazy or not lazy, a perfectly aligned eye can also be lazy. Each must be treated individually on a case-by-case basis.

Early Detection and Intervention

Strabismus and amblyopia are two interconnected eye conditions that can significantly impact an individual’s vision and quality of life, particularly when they occur in childhood. Early detection, intervention, and regular eye examinations, both in infancy and throughout childhood, play a pivotal role in effectively managing these conditions and preventing long-term visual impairments.

An optometrist can provide a thorough evaluation, precise diagnosis, and a tailored treatment plan to optimise visual development and ensure a lifetime of healthy eyesight.

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