Amblyopia (Lazy Eye) / Strabismus (Turned Eye)

Amblyopia or lazy eye is a treatable form of vision loss. It occurs when the brain and eyes are not working together efficiently, causing reduced vision in one or both eyes. Because the neural connection from the lazy eye to the brain is decreased, this can sometimes result in a turned eye or strabismus, where the eye can turn up, down, in or out. This disruption in vision leads the brain to blunt the image coming in from one eye in favour of the other.

The decreased neural signal from the amblyopic eye to the brain can also lead to a turned eye. Alternatively, amblyopia can also occur the other way due to an image disruption through the turned eye. Therefore lazy eye and turned eye often occur hand in hand.

Non-surgical treatment for Strabismus

Source: Wow Vision Therapy
The most common indicator is an obvious difficulty with depth perception, has trouble catching and throwing objects, or is frequently bumping into things.

What Causes Amblyopia/Strabismus?

Amblyopia and strabismus typically develop during infancy and early childhood, but can also occur in adulthood after a traumatic brain injury. It affects approximately 3% of the world’s population.

The exact reason why amblyopia and strabismus develops is not definite, but it is thought to occur when the images coming through both eyes cannot be reconciled by the brain during a person’s development. The brain therefore develops a solution to the problem by suppressing, blurring, or turning one of the eyes out of the way. There can also be cases where the images of both eyes are affected, and the brain never develops the ability to see clearly with both of the eyes.

The human visual system is designed to use both eyes to explore visual space. When both eyes cannot see similarly and the brain can’t easily combine the images, the person loses many of the skills essential for good visual development.

 

What are the symptoms?

The human visual system is designed to use both eyes to explore visual space. When both eyes cannot see similarly and the brain can’t easily combine the images, the person loses many of the skills essential for good visual development.

Because amblyopia can look normal from the outside, it is difficult to detect by simple observation.  The most common indicators are:

  • Impaired depth perception
  • Poor hand-eye coordination
  • Frequent tripping or bumping into things
  • Trouble with processing visual information
  • Struggling with reading or comprehension

As children often don’t have a concept of what ‘normal vision’ is, it can go undiagnosed until their first eye test. Therefore some children can go through their whole schooling life never realising that they have it. Having one eye suppressed can impact on the development of visual processing skills, which in turn can prevent them from reaching their potential.

Esotropia strabismus
Exotropia strabismus

Image Source: Community Eye Health Journal

Lazy Eye / Turned Eye Treatment Options

Vision Therapy & Treatment Glasses

Vision Therapy and treatment glasses provided by a trained Behavioural Optometrist and Vision Therapist.

Patching

Patching, maximum plus glasses and surgical realignment provided by an Ophthalmologist.

Our Philosophy of Lazy Eye / Turned Eye Treatment

Our method of treatment for amblyopia and strabismus is vastly different from the recommendations of Ophthalmologists. This is the same method that is currently being taught in Optometry school at QUT, under the ‘paediatric special needs’ course of 4th and 5th year.

Please be aware that there are ophthalmologists, particularly in Queensland, who disagree with Vision Therapy to treat lazy eye and turned eye. This is because the philosophy behind Vision Therapy is not part of their training and they do not believe that therapy can help with strengthening the neural connections between the brain and eyes. This is why you may find that they will generally not support vision therapy.

At Grace & Vision Optometrist, we believe in the general medicine treatment principal. Non-invasive treatments should be the first-line of treatment, and invasive treatments, such as the irreversible structural changes during surgery, should be the second line.

Currently, the exact cause for strabismus is not completely known, and therefore an absolute cure does not exist. This is why this is the only area where there is a debate between optometrists and ophthalmologists on the best treatment plan. Because strabismus is a very complicated condition, we choose to do a more conservative approach with Vision Therapy.

The purpose of Vision Therapy is to assist patients in achieving maximum function with what they have. Our principle goal is to provide an opportunity for the eye to function at its best capacity. The fact that Vision Therapy inevitably prevents further deterioration (such as larger and more permanent eye turns) is an added bonus. In saying this, we have been able to help our own patients correct a 40 prism turn, to less than a 10 prism turn (which is virtually undetectable by most people and has the same outcome as surgery).

To date, 80% of our Vision Therapy patients have experienced large improvements and been empowered with the skills to gain more awareness and control of the eyes.

The exact degree of improvement can vary from patient to patient, but all have experienced:

  • improved visual clarity,
  • better eye movement control,
  • better eye teaming,
  • better focusing ability,
  • and reduced double vision.

The purpose of this informed consent form is to ensure you have a full understanding of your treatment options by highlighting the differences and expected outcomes of both methods.

Our Method vs. Ophthalmologist Method

1. Patching (covering the good eye to improve the visual acuity of the lazy eye)

Ophthalmologist method (patching only): The first treatment is often to prescribe patching for a few hours a day and reviewing progress in 12 months. Doing so has been shown to improve vision in the lazy eye; however, the likelihood of regression, once the patch has been removed, is high. This is because the fundamental issue causing amblyopia is that the two eyes are unequal and therefore find it difficult to work together. Patching alone and without any specific visual tasks does not necessarily mean that the information coming from each eye will become equal. This is why the “lazy eye” may inevitably regress once patching has stopped.

In most cases, Ophthalmologists commonly recommend patching and hope the child will work things out on their own for the next 12 months. Then if things don’t happen to work out, surgical intervention is recommended.

Behavioural Optometry method (patching and Vision Therapy):

We perform patching in conjunction with visual activities in a step-by-step manner to coach the eye to perform at its best, and eventually to learn to work with the other eye.  It is similar to teaching a baby the fundamentals of running: you must first crawl to be able to walk, and then be ready to run.

Step 1 in vision therapy is to work on accommodation (focusing), convergence (look close) and divergence (look far) of each individual eye (monocularly). Step 2 is to teach each eye to work independently from each other (bi-ocularly) without one eye over-powering the other. The final step 3 is to teach the eyes how to work together as a team (binocularly).

Vision Therapy may not 100% correct the turned or lazy eye, but we are at least giving the child a chance to rehabilitate their eyes to utilise the best of what they have, build self-confidence, and maximise learning potential.

2. How to Prescribe Glasses

Ophthalmologist: Ophthalmologists generally prescribe stronger plus prescriptions in glasses help the muscles around the eye to relax and therefore straighten the eye. This is done by administering cycloplegic eye drops to paralyse the eye’s focusing muscles so that the prescription can be obtained when the eye is at complete rest. However, providing this prescription can cause too much muscle relaxation and prevent the eyes from developing normally.

In most cases, Ophthalmologists commonly recommend patching and hope the child will work things out on their own for the next 12 months. Then if things don’t happen to work out, surgical intervention is recommended.

Behavioural Optometry: Research shows that children require slightly lower prescriptions to encourage emmetropization (giving the eyes room to develop to a normal level). This is why we will prescribe just enough plus power to relax and straighten the eye whilst still retaining muscle function in the eyes. This gives children the opportunity to use their eye muscles to participate in their vision. Doing so also lowers the chance of prescription rejection i.e. not wanting to wear the glasses.

We then regularly monitor the child’s progress and titrate the prescription as needed to provide the best balance between:

  1. clarity of vision, 
  2. straight eyes,
  3. visual needs (e.g. if starting school, they will need a prescription that provides more support for near work),
  4. and room for development and growth.

This means there is the possibility of changing the glasses prescription as the child’s visual demands change, which could range from three to twelve months. Since we don’t always give children the maximum prescription, we might not perform a cycloplegic refraction (stinging eye drops) every time.

2. Stabismus Surgery

Surgery is often recommended by ophthalmologists when patching hasn’t been successful. This means undergoing general anaesthesia to operate on the eye muscle to shorten and re-attach to the eye.

However, over time, we have seen in many cases that surgery can over-correct the eye turn i.e. go from turning inward to turning outward, or result in an upwards/downwards turn, or rotational turn. This will then require further surgeries to re-correct the eye’s alignment.

In many cases, a patient may need two or more surgeries to achieve good cosmetic alignment and more as they get older. Even if the eyes are almost straight but not perfect, they can not work together. This can cause double vision or suppression of one eye, and the brain can start to develop a lazy eye or turn the eye once more.

As the brain is ever-growing and learning, the brain can be trained how to more efficiently communicate with both eyes as a team, and effectively treat amblyopia and strabismus. Of course, some individuals do require surgical intervention, but Vision Therapy prior to surgery will improve the success of the surgery, and prevent the likelihood of multiple surgeries in the future. Vision Therapy after surgery is also beneficial to help stabilise the eyes in their new alignment.

As a mother of two children, I feel strongly about trying options that are non-invasive, and can give your child an opportunity to grow and develop themselves. This is why we believe Vision Therapy should be the first line of treatment to give the individual the chance to non-invasively teach their eyes how to coordinate together, and also to know their own bodies.

Once the irreversible changes of surgery have been made, it is hard to say how children cope with the sudden change of vision. As children often lack the sophistication and experience to express their frustrations, they may instead resort to anger, screaming, or disengaging from the world.

4. Critical Period of Treatment is Before 8 Years of Age

Historically in the 1960s, Nobel Prize-winning research using monkeys and cats were used to improve our understanding of binocular vision development. It theorised that there is a critical period for which treatment for strabismus and amblyopia must be done; after which it is no longer possible to develop binocular vision. However, in recent years, there have been many studies that disprove this theory, showing that it is entirely possible to treat strabismus and amblyopia well over age twelve.

Although the critical period does correlate with enhanced neuroplasticity (the ability for the brain to learn and change), the brain is very capable of neuroplasticity at any age. For example, if you learn to read Braille even as an adult, the number of neurons in your brain that receive touch input from your reading index finger increases.

The following papers indicate that significant visual plasticity does extend beyond a critical period in early life:

  • Levi DM. Perceptual learning in adults with amblyopia: a reevaluation of critical periods in human vision. Dev Psychobiol. 2005;46:222–232.
  • Bao S, Chang EF, Davis JD, Gobeske KT, Merzenich MM. Progressive degradation and subsequent refinement of acoustic representations in the adult auditory cortex. Journal of Neuroscience 23, 2003; 10765-75
  • Kasamatsu T, Matabe K, Heggelund P, Scholler E. Plasticity in cat visual cortex restored by electrical stimulation of the locus coeruleus. Neuroscience Research 2. 1085; 365-86
  • Keuroghlian AS, Knudsen ET. Adaptive auditory plasticity in developing and adult animals. Progress in Neurobiology 82. 2007; 109-21
  • Ostrovsky Y, Andalman A, Sinha P. Vision following extended congenital blindness. Psychological Science 17. 2006; 1009-14
  • Pascual-Leone A, Torres F. Plasticity of the sensorimotor cortex representation of the reading finger of Braille readers. Brain 116. 1993;39-52

What questions should I ask my ophthalmologist before surgery?

  • Will surgery cure amblyopia?
  • Will it help with learning difficulties?
  • Will my child be able to have 3D vision?
  • What is the likelihood of multiple surgeries?