Amblyopia, sometimes called 'lazy eye,' is a vision condition that develops in early childhood when neural pathways between the eyes and the brain are not functioning properly. This improper visual development occurs when certain visual factors are present in early life, causing decreased vision in one or both eyes. As the child is unable to see 20/20 from a very young age, the brain habituates to seeing the blurry image, thus impacting vision development. 

As amblyopia is the result of improper vision development, it does not respond to correction with glasses or contacts in the same way as an uncorrected prescription. This means that even with correction in place a child is unlikely to see 20/20. Amblyopia is a neurologically active process, meaning that vision must be treated by modifying the defective communication between the eyes and the brain.

Causes and Types of Amblyopia

Amblyopia occurs when an eye is prevented from seeing clearly in early life. Chronic blurred vision results in deficient neural pathways between the eyes and the brain and the resultant visual deficits characteristic of amblyopia.

There are different types of amblyopia that are classified by the cause of the reduced vision: 

REFRACTIVE AMBLYOPIA

Refractive amblyopia is caused by uncorrected refractive error (prescription) and the resultant blurry image that is transmitted to the brain. Refractive amblyopia occurs when large or unequal amounts of nearsightedness (myopia), farsightedness (hyperopia), or astigmatism go uncorrected in the early years of life. Refractive amblyopia can affect either one or both eyes, depending on the prescription.

Amblyopia is by far the most common cause of vision impairment in children. As refractive amblyopia is caused by an uncorrected prescription, it can easily be prevented with early intervention in the form of glasses. An eye examination with a residency-trained pediatric optometrist will determine if a prescription is present in a young child that is likely to cause refractive amblyopia. Our residency-trained pediatric optometrist, Dr. Jill Kronberg, performs dilated eye examinations on infants, toddlers, and children and routinely treats amblyopia at very young ages.

DID YOU KNOW?  The American Optometric Association recommends that all children have their first visit with the eye doctor before their first birthday.

Dr. Jill Kronberg received her residency training in pediatric optometry at the University of California, Berkeley. A comprehensive eye examination with a residency-trained pediatric optometrist can identify far more than a vision screening is able to. This allows for early diagnosis and treatment of childhood vision conditions, such as amblyopia.

DEPRIVATION AMBLYOPIA

Deprivation amblyopia is caused when a child is 'deprived' of clear vision due to a cataract, trauma, drooping lid, or other process. When vision is obstructed at a very young age, the brain is unable to develop the neural pathways appropriately and deprivation amblyopia results.

DID YOU KNOW?  Vision screenings miss as much as 66% of vision problems.

A comprehensive eye examination with a residency-trained eye doctor detects conditions affecting vision and development. It is important to remember that vision screenings at the pediatrician's office or at school do not replace the need for routine vision care and comprehensive eye examinations. Many childhood vision conditions are better treated when detected early in life.

Visual Effects of Amblyopia

Amblyopia affects much more than the ability to see 20/20. Vision is a complex process that involves 2/3 of the connections in the brain to produce vision, make sense of visual information (visual perception) and integrate vision with the other senses.

Amblyopia affects several aspects of vision, including:

ACCOMMODATION (Eye focusing)

Accommodation is often reduced in individuals with amblyopia, meaning that they have a difficult time making things clear or keeping them clear. This makes many aspects of classroom learning more difficult. 80% of learning occurs through vision, and when a child has a vision condition it can negatively impact learning. Difficulties with eye focusing can make copying notes from the board, reading and other near activities more difficult. While a child may be able to read an eye chart from across the room during a vision screening, they may find it extremely difficult to see clearly when trying to read and learn.

BINOCULAR VISION (Eye teaming)

Amblyopia is not only one eye seeing blurry but is also a form of binocular vision dysfunction, meaning the eyes have difficulty working together in a coordinated manner. The ability to use the two eyes together is a crucial visual skill. Difficulty with eye teaming results in a number of symptoms, including: double vision, headaches, eyestrain, difficulties with reading fluency, skipping or re-reading lines of text, words moving on the page, difficulty concentrating during visual tasks and fatigue. Optimum binocular vision functioning is important for both academic and athletic success.

CONTRAST SENSITIVITY (Ability to distinguish differing shades of gray)

Contrast sensitivity is an important aspect of vision. Low levels of contrast sensitivity impair mobility. Contrast sensitivity helps one judge the terrain. For someone with poor contrast sensitivity a sloped incline and a set of stairs may look the same, making it difficult to navigate through the world. Conversely, excellent contrast sensitivity helps athletes track moving objects and perform at high levels.

DEPTH PERCEPTION (3D vision)

Depth perception is important for many reasons. For some, the ability to see depth lets them enjoy their favorite movie in 3D. For others, depth perception is important for work or hobbies. Depth perception is important for everything from driving, hitting a baseball, and threading a needle. The importance of depth perception is easily realized by covering one of your eyes. It is much more difficult and uncomfortable to move through the world while only using one eye.

SUPPRESSION (Ignoring one eye)

Suppression is a neurological response to stress on the binocular vision system. When amblyopia is present, one eye may see much better than the other. This creates a situation where the brain begins to ignore the visual input from the lesser-seeing eye. With time the brain begins to rely on the visual input from the better-seeing eye to eliminate double vision, eyestrain, or other symptoms. Suppression must be properly treated to restore proper binocular vision functioning.

VISUAL-MOTOR INTEGRATION (Eye-hand coordination, gross motor and fine motor abilities)

When amblyopia negatively impacts the aspects of vision just discussed, it also makes motor tasks more difficult. Many motor tasks are driven by the eyes and vision. The eyes tell the body when and how to react. People with amblyopia may appear clumsy or have difficulty with athletics. It is possible for someone with amblyopia to achieve some success with visual-motor tasks, however it is extremely difficult for them to achieve their full potential.

VISUAL-AUDITORY ABILITIES (Ability to connect visual and auditory information)

If a child with amblyopia sees someone mouth a word, what they hear can actually be different from what was said. When a child is learning they are required to match visual materials (pictures, words, etc) with auditory materials (the sound of the word, etc). A pilot study recently published in the Journal of the American Medical Association - Ophthalmology indicated that children who have amblyopia may also have impaired visual-auditory speech perception. 

Treatment of Amblyopia

The specific treatment protocol developed by your doctor depends on the specific type of amblyopia as well as several factors that will be evaluated during the examination. Overall, the treatment protocol will progress through three phases of intervention to provide improved visual functioning. 

The three phases:

ADDRESS THE INITIAL CAUSE OF THE AMBLYOPIA

For refractive amblyopia, the underlying cause is an uncorrected refractive error. The first step is for the doctor to prescribe full-time glasses to correct nearsightedness, farsightedness or astigmatism. It is important to remember that even after the vision is corrected to 20/20 your child will still need to correct their vision full-time with glasses or contacts.

For strabismic amblyopia, the underlying cause is an eye turn. The eye turn must be corrected (typically with surgery) in order to then address the amblyopia. Although a strabismus surgery (eye muscle surgery) does not guarantee that binocular vision will be achieved, it does allow for closer alignment of the eyes.

For deprivation amblyopia, it is important to remove the obstruction to clear vision. For example, if vision is obstructed by a cataract the surgeon will remove the cataract and allow for a clear image to reach the retina. 

IMPROVE VISION IN THE AMBLYOPIC EYE

When one eye is affected by amblyopia, occlusion therapy is used to improve the vision in the amblyopic eye. Occlusion therapy consists of using an eye patch or medicated eye drops (pharmacological occlusion) to block the better-seeing eye. This creates a situation where the lesser-seeing amblyopic eye is forced to perform visual tasks. Over time, and communication between the brain and the eye improves, the vision begins to improve.

Extensive research has been conducted regarding the treatment of amblyopia. Most notably, the Pediatric Eye Disease Investigator Group (PEDIG) has conducted several clinical trials that have shown both patching and medicated eye drops to be effective in the treatment of amblyopia. The choice of therapeutic approach and exact amount of occlusion therapy required depends on the case. Our doctors use a research-based approach to treating amblyopia and will help determine the most effective treatment protocol for your child.

IMPROVE BINOCULAR VISION FUNCTIONING

Amblyopia negatively impacts the ability to use both eyes together, thus it should be viewed as a form of binocular vision dysfunction. When treating amblyopia it is important to recognize the effects on binocular vision, including suppression, impaired depth perception, accommodative dysfunction, vergence dysfunction, and the effects on visual integration. Treatment of amblyopia is incomplete if binocular vision dysfunction is not addressed.

In-office vision therapy is used to improve binocular vision dysfunction in those with amblyopia. Vision therapy effectively addresses suppression and other binocular vision deficits where glasses and occlusion therapy cannot. While it may be important to isolate the amblyopic eye during occlusion therapy to improve vision, working with one eye does not support a binocular (two eyed) system as vision therapy is able to. Vision therapy allows amblyopic patients to achieve higher levels of binocular vision and positively affect visual performance.

When choosing a vision therapy program it is important to choose a program conducted under an optometrist who is residency-trained in binocular vision, neuro-optometry, and vision therapy. It is also important to choose a program that uses a research-based approach to treatment and employs licensed therapists who work one-on-one with the patient. Advanced Vision Therapy Center is Idaho's recommended vision therapy center.

DID YOU KNOW?  Treatment of amblyopia is effective in children and adults

It was once believed that treatment of amblyopia was only possible for young children. As more clinical trials have been performed and more research has been published, it is now known that amblyopia can be treated at any age. Both children and adults respond well to treatment and see improvement in vision and binocular vision functioning.

Whether you are a child or an adult, it is important to work with an eye care professional who specializes in pediatrics, binocular vision, and vision therapy. At Artisan Pediatric Eyecare, our team of doctors includes Dr. Jill Kronberg, Idaho's first residency-trained pediatric optometrist, and Dr. Ryan Johnson, Idaho's first residency-trained neuro-optometrist. 

Strabismic Amblyopia

Strabismic amblyopia is caused by certain types of strabismus, or eye turn. With strabismus, one eye turns in, out, up or down. When the eye is turned relative to the other it interferes with normal binocular vision functioning. As a result of this eye misalignment amblyopia develops in one eye. Along with reduced vision, the brain also develops suppression, a process by which the visual input from one eye is ignored by the brain. Suppression cannot be treated with glasses, contacts, or LASIK and instead one must restore binocular vision functioning through an active process.

DID YOU KNOW?  The American Optometric Association recommends a child's second eye examination occur at three years old.

Strabismus is one of the many vision conditions that can be identified during a comprehensive eye examination. There are several treatments available for strabismus, including glasses, vision therapy, and surgery. Dr. Ryan Johnson received his residency training in binocular vision, neuro-optometry, and vision therapy at the University of California, Berkeley. He is the first optometrist in Idaho with this advanced training in these areas. He routinely manages patients with strabismus, determining how the condition has affected their visual functioning and the most appropriate treatment method for their specific type of strabismus.

Visual Acuity (Clarity of vision)

Individuals with amblyopia experience blurry vision in one or both eyes. When present in one eye, a child may adopt an abnormal head posture (tilt or turn) to compensate for the vision in one eye. When present in both eyes, a child may sit closer to the television or hold a book closer than expected when reading. Children with blurry vision rarely complain because their level of visual functioning is 'normal' for them. Children with one blurry eye complain even less often because they are able to use their better-seeing eye to perform daily tasks.

If you're looking for highly-trained pediatric optometrists to treat or diagnose your child's amblyopia, then call us at 208-900-3336.