Types of Lazy Eye

Amblyopia, commonly called lazy eye, is the most common type of vision impairment in children.⁸ It causes poor vision in one eye due to improper visual development early in life. There are various types of lazy eye that have different causes and treatment needs.

People with amblyopia have normal eyes, but the brain favors one eye over the other. As the brain continues to rely on one eye, vision in the other eye gets worse. Rarely, this can affect both eyes. Without treatment, it can lead to partial or total vision loss.

Development of amblyopia usually occurs between birth and 7 years of age. About 2% to 3% of people have amblyopia.⁸

Types of Lazy Eye

There are three main types of lazy eye:

Strabismic Amblyopia

Strabismic amblyopia is the most prevalent type of lazy eye. This type occurs when one eye turns in or out.

Strabismus is a muscle imbalance that causes the eyes to cross in or turn out. When the eyes aren’t aligned, they don’t work together properly. 

Children with strabismus may develop amblyopia if the brain stops registering visual information from the misaligned eye.

Refractive Amblyopia

Refractive amblyopia occurs when the eyes have a significant difference in vision. 

This type of lazy eye is typically due to farsightedness (hyperopia). However, it can result from other refractive errors, such as:

• Nearsightedness (myopia)
• Astigmatism

These vision problems are usually easy to fix with eyeglasses or contact lenses. Left untreated, the brain may start to favor the eye with better vision, leading to amblyopia.

Deprivation Amblyopia

This is usually the most severe type of lazy eye. Deprivation amblyopia is when a problem in one eye—such as a cataract—causes impaired vision in that eye. 

Although cataracts are common in older adults, infants with deprivation amblyopia require urgent treatment to prevent vision loss.

What Causes Lazy Eye? 

Anything that interferes with normal vision during a child’s development can lead to a lazy eye. Amblyopia occurs when the brain begins ignoring visual signals from the eye with the worse vision.

Some children are at a higher risk of developing a lazy eye. These include children who have:¹

• A family history of amblyopia
• Developmental disabilities
• Complications at birth (including premature birth)

Several types of vision issues can cause a lazy eye:

Refractive Errors

Certain refractive errors can cause a lazy eye. They include:

• Nearsightedness (myopia). This refers to difficulty seeing objects at a distance.
• Farsightedness (hyperopia). This refers to trouble seeing things up close.
• Astigmatism. This refers to a curve in the cornea that causes blurred or distorted vision.

Strabismus

Childhood strabismus can lead to other eye problems like amblyopia. To avoid double vision, a child’s brain may ignore images from the misaligned eye. This prevents the eye from developing normal vision.

Physical Eye Problems

Any eye condition that causes reduced vision or vision loss in one eye can lead to amblyopia. Examples include:

• Childhood cataracts (congenital cataracts)
• Droopy eyelids (ptosis)
• Corneal ulcers
• Eye injuries
• Glaucoma
• Eye surgery

Symptoms of Lazy Eye

Unlike strabismus, amblyopia is difficult to notice with a simple observation. But some signs may indicate amblyopia in children. 

Children with amblyopia may display poor depth perception by not knowing how near or far an object is. You may notice other signs that your child is having difficulty seeing clearly, such as:

• Squinting
• Tilting their head
• Shutting one eye

Most of the time, parents aren’t aware their child has amblyopia until a doctor diagnoses it during an eye exam. That’s why all children should have a vision screening by their fourth birthday.

Treatment

Amblyopia treatment is most effective when started as early as possible. Constant suppression of signals from the lazy eye can lead to vision loss in that eye. After a child turns 8, the chances of vision improvement drop dramatically.

There are two approaches to amblyopia treatment:

• Addressing the underlying eye problem
• Training the lazy eye to work so it can develop normally

Treating Underlying Eye Problems

When amblyopia is due to a refractive error or physical eye problem, treatment may include:

Corrective Lenses

Sometimes, corrective eyewear is all it takes to treat amblyopia. Eyeglasses and contact lenses can correct refractive errors like:

• Nearsightedness
• Farsightedness
• Astigmatism

A child needs to wear their glasses or contacts consistently for the treatment to be effective.

Surgery

Eye surgeries that may treat various types of amblyopia include:

• Cataract surgery. To remove a clouded lens and restore clear vision.
• Eyelid surgery. To treat a droopy eyelid.
• Strabismus surgery. To correct eye alignment.

Training the Lazy Eye

There are several ways to train a lazy eye. Here are four options:

Eye Patch

Your child may cover the better-seeing eye with a patch to stimulate the weaker eye, making it stronger over time. They wear the eye patch for 2 to 6 hours a day or more.

Bangerter Filter

This special filter is an alternative to an eye patch and achieves the same goal of stimulating the weaker eye. A Bangerter filter fits over the eyeglass lens of the dominant eye.

Eye Drops

Atropine eye drops cause temporary blurry vision in the stronger eye. Similar to using a patch or filter, this approach encourages using the weaker eye.

Side effects of atropine include eye irritation and sensitivity to light.

Vision Therapy Exercises

Vision therapy exercises like eye movement control and strengthening techniques can help strengthen vision in the weaker eye.

Outlook

The outlook for amblyopia depends on how early treatment begins—the sooner, the better.

Without  treatment, a lazy eye can worsen. If the brain continues suppressing images from the lazy eye, permanent vision loss may occur. 

Treatment before age 8 is necessary to provide the best chances of preserving a child’s vision.

Can You Prevent Amblyopia? 

Some lazy eyes are preventable. If your child has strabismus or a structural eye problem, you may be able to treat it before it leads to amblyopia.

In other cases, treatments like eye drops or eye patches can help strengthen the weaker eye. But the lazy eye might always be slightly weaker than the other.

Summary

Amblyopia, or lazy eye, occurs when the nerve pathways between the brain and eye don’t develop properly in childhood. 

Amblyopia is very common, especially if you have a family history of eye problems. Having one weaker eye can cause blurred vision and other issues.It is important to treat amblyopia as early as possible. An early childhood eye exam can diagnose this condition.