Amblyopia: Definition, Types, Symptoms, Causes, Diagnosis, Treatment, Investigation and Outlook

You probably know this childhood eye condition by its more common name, lazy eye.

It happens when the vision in one of your child’s eyes does not develop as it should.

If left untreated, your child’s brain will learn to ignore the image coming from that eye. That could permanently damage your vision.

Amblyopia or lazy eye is a common eye condition found in about 1 in 30 people. It is usually caused by an undetected need for glasses in an infant or young child, but it can be the result of an eye roll.

When one eye has normal sight and the other has poor sight, the person learns to see through the eye with good sight. Vision in the weaker eye does not grow and develops as the child grows. This can affect the ability of both eyes to coordinate efficiently.

Some children seem unaffected by this when they are young, but when they are older they may have problems with school and athletic performance.

If left untreated, amblyopia can affect a child’s self-image, work, school, friendships, and can also lead to depression .

Amblyopia produces a lack of depth perception and teaming in the eyes, focus, and tracking. These difficulties can result in struggles at school or uncertainty in daily activities and sports.

Later in life, an adult with amblyopia may be restricted in the careers of their choice.

Office-based vision therapy programs offer the highest cure rates for lazy eye compared to eye surgery, lenses alone, or patches without therapy.

Children do not want to wear the eye patch because it affects their quality of life and other treatment methods such as eye drops can cause sensitivity to light and disorientation.

As a result, amblyopia does not always go away with patch therapy alone.

Even the patient who has undergone patch therapy will generally have a condition, known as suppression, in which the amblyopic eye turns off, resulting in stereo blindness and poor depth perception, being prone to accidents and poor eye coordination. -hand.

The first step is to get a pair of glasses or goggles that can be worn comfortably. This starts the process of correcting the original problem in one eye so that you can see more clearly than the other.

So the ability for the two eyes to work together as a team must be developed through an individualized vision therapy program. The person may still need glasses after completing the vision therapy program.

The goal is for the patient to have normal vision, eye teaming, eye focus, and eye movement skills.

The earlier the condition is found and treated, the better the functional outcome; however, our office successfully treats patients into adulthood.

Vision therapy should be started with anyone who does not have 20/20 vision with glasses or contact lenses in each eye or anyone who has impairments in any of the visual skills necessary for visual success.

Types and symptoms

Amblyopia has three main causes:

Strabismus : due to strabismus (misaligned eyes).

Refractive : by anisometropia (difference of a certain degree of myopia, hyperopia or astigmatism), or by a significant amount of equal refractive error in both eyes.

Private : from vision deprivation early in life from disorders that obstruct vision, such as congenital cataract.

Amblyopia extremism

Strabismus, sometimes also incorrectly called lazy eye, is a condition in which the eyes are misaligned.

Strabismus usually results in normal vision in the preferred observing (or ‘companion’) eye (the eye the person prefers to use), but can cause abnormal vision in the deviated eye or strabismus due to the difference between the images that they are projected to the brains of both eyes.

Adult-onset strabismus usually causes double vision (diplopia), as the two eyes are not fixed on the same object.

Children’s brains, however, are more neuroplastic, so they can more easily adapt by suppressing images from one of the eyes, eliminating double vision.

This plastic response of the brain, however, disrupts normal brain development, resulting in amblyopia. Recent evidence points to a cause of infantile strabismus that lies with the entrance to the visual cortex.

Those with strabismic amblyopia tend to show eye movement deficits when reading, even when using the non-adlopopic eye.

In particular, they tend to do more pulls per line than people with normal stereoscopic vision, and have a reduced reading speed, especially when reading text with a small font size.

Strabic amblyopia is treated by clarifying the visual image with glasses, or by encouraging the use of the amblyopic eye with a patch on the dominant eye or the pharmacological penalty of the better eye.

The penalty generally consists of applying atropine drops to temporarily paralyze the accommodation reflex, leading to blurred vision in the good eye.

It also dilates the pupil. This helps prevent bullying and teasing associated with wearing a patch, although applying eye drops is sometimes challenging.

The ocular alignment itself can be managed with surgical or nonsurgical methods, depending on the type and severity of the strabismus.

Refractive or anisometropic amblyopia

Refractive amblyopia can be the result of anisometropia (uneven refractive error between the two eyes).

Anisometropia exists when there is a difference in power between the two eyes. The eye that provides the brain with a clearer image typically becomes the dominant eye.

The image in the other eye is blurred, resulting in abnormal development of one half of the visual system.

Refractive amblyopia is usually less severe than strabismic amblyopia and is often overlooked by primary care physicians because of its less dramatic appearance and lack of obvious physical manifestation, as with strabismus.

Since refractive correction of anisometropia by means of glasses generally leads to a different image magnification for the two eyes, which in turn can prevent binocular vision, a refractive correction with contact lenses should be considered.

Pediatric refractive surgery is also a treatment option, particularly if conventional approaches have failed due to aniseikonia or non-compliance or both.

Amblyopia is often associated with a combination of anisometropia and strabismus. In some cases, the vision between the eyes may differ to the point where one eye has twice the average vision while the other eye is completely blind.

Privatization and occlusive amblyopia

Withdrawal amblyopia (amblyopia ex anopsia) occurs when the ocular media becomes opaque, as in the case of congenital cataract or corneal clouding.

These opacities prevent adequate visual input from reaching the eye and disrupt development. If not treated promptly, amblyopia can persist even after removing the cause of the clouding.

Sometimes a drooping eyelid (ptosis) or some other problem causes the upper eyelid to physically occlude a child’s vision, which can quickly cause amblyopia.

Amblyopia due to occlusion can be a complication of a hemangioma that blocks part or all of the eye.

Other possible causes of occlusion deprivation and amblyopia include vitreous obstruction and aphakia. Deprivation amblyopia accounts for less than 3% of all people affected by amblyopia.

What causes it?

Amblyopia usually begins when one eye has much better focus than the other. Sometimes one has more farsightedness or astigmatism, but the other does not.

When your child’s brain gets both a blurry and a clear image, it begins to ignore the blurriness. If this continues for months or years in a young child, the vision in the blurry eye will worsen.

Sometimes a child’s eyes don’t line up the way they should. One could go in or out. The doctor will call this strabismus and it can also lead to amblyopia. Children who have it cannot focus their eyes on one image, so they often see twice as much.

If your child has it, his brain will ignore the image of the eye that is not aligned. The vision in that eye will get worse. It is this misalignment that led to the term “lazy eye.”

Some children cannot see well with one eye because something is blocking the passage of light. It could be a cataract or a small amount of blood or other material at the back of the eye.

How is amblyopia diagnosed?

All children should be tested before reaching school age. Your child’s doctor or the vision program at the school will verify that:

  • Nothing blocks the light that enters your eyes.
  • Both eyes see equally well.
  • Each eye moves as it should.

If there are any problems, your doctor or school nurse may suggest that you take you to an eye doctor. If you feel that something is wrong with your child’s vision, even if nothing shows up on the eye exam, make an appointment with a pediatric eye doctor.

Some eye care experts say that children should have an eye exam at 6 months, 3 years, and then every year while they are in school. Ask your doctor what is right for your child.

If the family has amblyopia, your child is more likely to have it. Remember, you can’t tell just by looking at her if she has it. Early diagnosis and treatment are the key to getting good results.

How is it treated?

The most common method is to force your child’s brain to start using the weak eye. First, the doctor will correct any underlying problems in that eye, such as nearsightedness, farsightedness, or astigmatism.

Most children with amblyopia also need glasses to help focus their eyes. If a cataract blocks the light from your eye, your doctor may recommend surgery to remove it.

Follow the doctor’s instructions carefully and take your child to scheduled visits so the doctor can see how the treatment is working.

In mild cases of amblyopia, the doctor may suggest the use of an eye drop called atropine. Erase the strong eye so your child does not need to wear a patch.

If strabismus keeps your eyes from moving the way they should, your doctor may recommend surgery on your eye muscles. You can talk about which treatment is best for her.

Treatment of anisometropia and refractive errors should occur next. The amblyopic eye must have the most precise optical correction possible. This should happen before any occlusion therapy because vision can improve with glasses alone.

This improvement is frequently seen in patients with unilateral refractive amblyopia.

Complete cycloplegic refraction should be administered to patients with accommodative esotropia and amblyopia. In other patients, a prescription less than the full plus refracted measurement may be prescribed since the decrease in plus is symmetrical between the two eyes.

Because accommodative range is believed to be decreased in amblyopic eyes, care must be taken to reduce the amount too much too much. Refractive correction alone has been shown to improve amblyopia in up to a quarter of patients in a nationwide trial.

Patients with bilateral refractive amblyopia do well with spectacle correction alone, with most 3- to 10-year-olds achieving 20/25 or more within a year.

The next step is to force the use of the amblyopic eye through occlusion therapy. Occlusion therapy has been the foundation of treatment since the 18th century. The following are general guidelines for occlusion therapy:

Patches can be full-time or part-time. The standard teaching has been that children should be observed at intervals of 1 week per year of age, if they undergo occlusion full time to avoid occlusive amblyopia in the good eye.

Amblyopia Treatment Studies (ATS) have helped provide new information on the effect of various amounts of patches.

Always consider non-compliance in a child where visual acuity is not improving. Compliance is difficult to measure, but it is an important factor in determining the success of this therapy.

In addition to adhesive patches, opaque contact lenses, eyeglass-mounted occluders, and eyeglass tape were used.

It is important to establish that the vision of the better eye has degraded sufficiently with the chosen therapy.

Amblyopia treatment studies have helped define the role of the full-time patch versus the part-time patch in patients with amblyopia.

Studies have shown that, in patients aged 3-7 years with severe amblyopia (visual acuity between 20/100 and 20/400), full-time patching produced an effect similar to that of 6 hours of patching per day.

In a separate study, 2 hours of daily patches produced an improvement in visual acuity similar to that of 6 hours of daily patches when treating moderate amblyopia (visual acuity better than 20/100) in children aged 3 to 7 years.

In this study, the patch was prescribed in combination with 1 hour of close visual activities.

Data from amblyopia treatment studies are also available for older patients, although patients younger than 7 years are the best responders to treatment.

For patients between 7 and 12 years old, studies of treatment with amblyopia suggest that prescribing 2 to 6 hours a day of patching can improve visual acuity, even if the amblyopia has been previously treated.

Among patients aged 13-17 years, the prescription of 2-6 hours a day of patch improves vision in 47% of patients whose amblyopia had not been previously treated and improves vision in 25% of patients whose amblyopia it had previously been treated with patches.

Amblyopia treatment studies have also found that about a quarter of children with amblyopia who were successfully treated experience a recurrence within the first year after stopping treatment.

Data from these studies suggest that patients treated with 6 or more hours per day of patching are at increased risk of recurrence when the patch is stopped abruptly rather than when it is reduced to 2 hours per day before the patch is stopped.

There is some evidence that having children wear an eye patch for 6 hours a day instead of 2 hours can lead to greater improvement in visual acuity at 10 weeks.

The significantly greater improvement in visual acuity seen with the more intense patching protocol suggests that this strategy is worth considering in children with residual amblyopia. The results have the following implications:

If there is stable residual amblyopia after 12 weeks of 2-hour patching, an increase to the 6-hour patch may produce further improvement.

If the goal is to achieve the best result in the shortest amount of time, it may be worth skipping the 2-hour patch and starting with the 6-hour patch.

In the past, penalty therapy was reserved for children who did not wear a patch or where compliance was an issue.

Amblyopia treatment studies, however, have shown that atropine penalty in patients with moderate amblyopia (defined by the study as visual acuity better than 20/100) is as effective as patch.

Amblyopia treatment studies were conducted in children aged 3 to 7 years.

Amblyopia treatment studies have also shown that weekend atropine use provided an improvement in visual acuity similar to daily atropine use when treating moderate amblyopia in 3- to 7-year-old children.

Atropine drops or ointment are instilled into the non-amlomopic eye. This therapy is sometimes used in conjunction with eyeglass patching or occlusion (such as tape, nail polish) by individual practitioners.

In amblyopia treatment studies evaluating patching versus atropine penalty, atropine penalty and patching were used in conjunction with 1 hour of near vision activities.

This technique can also be used for maintenance therapy, which is helpful, especially in patients with mild amblyopia.

Other options include optical blur through contact lenses or raised bifocal segments.

In a prospective cohort study of 105 children who had previously participated in a randomized trial that compared atropine and patch for moderate amblyopia.

The researchers observed, after controlling for the initial refractive error, a decrease in the amblyopic equivalent spherical refractive error at less farsightedness.

This shift toward emmetropia was associated with ocular alignment, supporting the idea that better motor and sensory fusion promotes emmetropia.

The desired end point of therapy is spontaneous alternation of fixation or equal visual acuity in both eyes.

When visual acuity is stable, patching may decrease slowly, depending on the child’s tendency for amblyopia to reappear.

There is no set standard for tapering the treatment of patches.

Because amblyopia recurs in a large number of patients (see Prognosis), maintenance therapy or treatment reduction should be seriously considered.

This narrowing is controversial, so individual physicians vary in their approaches.

Although there have been many advances in the treatment of amblyopia, tailoring treatment with individual treatment plans remains difficult because the dose / effect response of the amount of occlusion is not fully understood.

Treatment of strabismus generally occurs last. The end point of strabismic amblyopia is free alternating fixation or equitable vision. Surgery is usually done when the end point has been reached.

epidemiology

Between 2 and 5% of the population in Western countries have amblyopia. In the UK, 90% of child eye appointments are related to amblyopia.

Depending on the criteria chosen for diagnosis, between 1 and 4% of children have amblyopia.

Investigation

A 2009 study, widely reported in the popular press, has suggested that repetitive transcranial magnetic stimulation can temporarily improve contrast sensitivity and spatial resolution in the affected eye of adults with amblyopia.

This approach is still under development and the results await verification by other researchers.

It has also been suggested that comparable results can be achieved using different types of brain stimulation, such as anode transcranial direct current stimulation and repetitive theta transcranial magnetic stimulation (rTMS).

A 2013 study concluded that convergent evidence indicates that uncorrelated binocular experience plays a critical role in the genesis of amblyopia and associated residual deficits.

Another 2013 study suggests that playing a version of the popular Tetris game that is modified so that each eye sees separate components of the game may also help treat this condition in adults.

Furthermore, it has been proposed that the effects of this type of therapy can be further enhanced by non-invasive brain stimulation, as shown in a recent study using transcranial anode direct current stimulation (tDCS). .

A 2014 Cochrane review sought to determine the effectiveness of occlusion treatment in people with sensory deprivation amblyopia, but no trials were found eligible to be included in the review.

However, the good results of occlusion treatment for sensory deprivation amblyopia probably depend on adherence to treatment.

What is the long-term outlook?

With early diagnosis and treatment, most children will gain vision. Amblyopia becomes much more difficult to treat after age 7-9, so make sure your child has eye exams early on.

And follow your doctor’s advice on treatment, even when it’s difficult. Most children don’t want to wear an eye patch every day. Ask your doctor if atropine is an option for your child.