Anisometropic Amblyopia

Having already discussed amblyopia in general, its molecular basis, and the ways of treating it, we shall now discuss perhaps the most tricky of all amblyopia conditions: anisometropic amblyopia.

In this guide, we will explain anisometropic amblyopia, clarify the difference between anisometropia vs amblyopia, and explore symptoms, diagnosis, and treatment options to help you recognize and address the condition early.

What is Anisometropic Amblyopia?

Anisometropic amblyopia is a type of amblyopia that develops due to untreated anisometropia.

As the name suggests it is amblyopia that arises due to anisometropia. You are probably asking yourselves what anisometropia is then.

Anisometropia is simply an expression that describes the difference in the refractive power of the two eyes.

In other words, it occurs when the two eyes have different glasses prescription, resulting in unequal focus between the eyes. This is frequently caused by one eye being somewhat larger or smaller than the other.

Anisometropia vs Amblyopia: What’s the Difference?

Understanding anisometropia vs amblyopia is essential.

Anisometropia is a refractive problem. It describes unequal prescriptions between the eyes. It does not automatically mean vision loss.

Amblyopia, on the other hand, is a neurodevelopmental condition. It occurs when the brain does not fully process input from one eye, resulting in reduced best-corrected vision.

In simple terms:

• Anisometropia = unequal focus
• Amblyopia = reduced brain-eye connection

How Common Is Anisometropic Amblyopia

Anisometropic amblyopia might not be the most prevalent. According to some authors, its prevalence is second to the strabismic one.

However, others report that up to 50% of cases of amblyopia are due to anisometropia.

Nonetheless, it is one of the hardest to recognize. The prevalence of anisometropia varies with age, with adults having a higher prevalence than children.

Causes and Risk Factors

The primary cause of anisometropic amblyopia is a significant refractive difference between the eyes.

Risk factors include:

• Family history of refractive errors
• Premature birth
• Lack of early vision screening
• Uncorrected prescription differences

If there is a notable difference in the refractive power of the two eyes, one retina gets a much clearer image than the other, which leads to the development of amblyopia in the eye with the lesser image quality.

”Differences in refraction between the two eyes can lead to the development of amblyopia.”

Due to high brain plasticity in children, the lesser quality image can be easily suppressed and children usually do not notice any abnormalities. According to the American Academy of Ophthalmology, anisometropia is likely to trigger amblyopia if refractive differences between the two eyes are greater than:
– 1.50 D of hyperopia (plus diopter),
– 2.00 D of astigmatisms (cylinder diopter),
– and 3.00 D of myopia (minus diopter). 

Symptoms of Anisometropic Amblyopia

One of the biggest challenges with anisometropic amblyopia is that symptoms are subtle.

In deprivation amblyopia, for instance, lens opacification is rather apparent by white pupillary reflex (leukocoria) on screening eye examination. Similarly, when the amblyopia etiology is strabismic, eye misalignment is usually easily recognized and children are soon referred to an ophthalmologist for examination.

In anisometropic amblyopia, though, there are no apparent abnormalities evident to the naked eye. Thus, in many cases, it is only recognized and addressed later, which is why it often requires more aggressive treatment.

”The eyes of children with anisometropic amblyopia appear perfectly normal to the naked eye.”

However, if you have long-term untreated anisometropia, you may experience the following symptoms:
– Double vision (diplopia),
– Blurred vision,
– Headaches,
– Poor depth perception,
– Dizziness,
– Eye pain.

Anisometropic Amblyopia: How is it Diagnosed?

In most countries, vision screening examinations at the pediatrician’s office or in the school system catch those children and refer them to an ophthalmologist so that amblyopia caused by anisometropia can be addressed early enough.

How is the anisometropic amblyopia diagnosed?

Diagnosis begins with a comprehensive eye examination.

Amblyopia can be discovered by assessing natural and corrected visual acuity with standard or optotype charts. Moreover, screening tests for stereopsis can quickly detect stereopsis deficits linked with amblyopia and anisometropia.

Treatment options

Once diagnosed, the treatment approach for anisometropic amblyopia is like any other amblyopic etiology, with an emphasis on the refractive correction that will eliminate amblyogenic anisometropia.

1. Glasses:

The first and most important step is full refractive correction.

Some children will respond to refractive correction alone, meaning wearing glasses or contact lenses. This may be all that the brain need to begin using both eyes simultaneously.

However, if the vision the in the amblyopic eye does not improve sufficiently with glasses, you will need to encourage the brain to pay attention to the weak eye with additional approaches.

2. Eye patching, penalization and vision therapy

Other individuals will benefit from the addition of patching, penalization and/or vision training.

One of the most important factors of treatment is compliance. To get the functional benefits of a therapy, some studies suggest the best visual acuity is achieved after 150 to 250 cumulative hours of therapy and 3 to 5 months for the amblyopia to be treated or stabilized. AmblyoPlay vision training is perfectly tackling the compliance problem.

Is your kid not motivated to do vision therapy? AmblyoPlay is here to help individuals achieve optimal compliance through fun and engaging therapeutic exercises. It is a gamified vision therapy performed through a tablet or computer for thirty minutes a day, specializing in treating amblyopia.

What to Expect From Treatment

The prognosis is generally very good when the condition is recognized early and addressed soon.

Furthermore, the earlier the treatment, the better the chance of enhancing the brain-eye connection.

Consequently, the outcome is heavily influenced by:
– the age at which therapy is initiated,
– whether treatment is carried out as prescribed,
– and how the glasses prescription varies over time.

Thus, frequent and thorough screenings are crucial in order not to leave the refractive differences unrecognized. 

Conclusion

Anisometropic amblyopia, characterized by unequal vision between the eyes, can significantly impact an individual’s daily life.

Understanding the prevalence, causes, symptoms, diagnosis, and available treatment options is essential for early detection and intervention.

During the treatment, compliance plays a major role in achieving desired results. AmblyoPlay vision therapy can be one of the treatment options for anisometropic amblyopia.

Frequently Asked Questions