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Amblyopia Treatment - Then and Now 

The definition of amblyopia to the majority of medical professionals is: Partial or complete loss of vision in one eye caused by a condition that affects the normal development of vision, in the absence of ocular pathology and which does not improve with the use of corrective lenses. Amblyopia is the most common cause of preventable blindness and, according to the World Health Organization, affects 1-5% of the world's population, including 12 million children under the age of 15. It has been given the layman's term, "lazy eye". 
But developmental optometrists see amblyopia in a different light and there is a growing body of research emerging which acknowledges that amblyopia is more than just an eyesight or acuity problem and is, in fact, a problem of binocular vision which affects the whole brain, not just one eye. The condition therefore must be treated binocularly, not monocularly as is the current standard of care among most optometrists and ophthalmologists. 
All professionals agree that amblyopia is not caused by a disease process, but rather by a lack of development of the visual brain - the child has healthy eyes, but the brain "cannot see". Interference in an infant's binocular visual development results in decreased acuity in the affected eye. The most common causes of amblyopia are strabismus (crossed eyes), unequal refractive errors (a high prescription in one eye and little to no prescription in the other eye) and obstruction of the visual axis creating form deprivation (ex: from cataracts, corneal opacity and/or eyelid ptosis). 
So despite the broad understanding that amblyopia ultimately stems from a disruption to binocular vision, why is the gold standard of treatment, that has been in practice for over 100 years, still monocular occlusion therapy (patching) to improve the eyesight? 
The traditional gold standard of care for amblyopia consists of prescribing the full refraction amount in the glasses with or without full or part-time patching. Proponents of the patching methodology believe that patching the "good eye" for hours on a daily basis (often for months to years at a time) will strengthen and improve the acuity in the "bad eye". According to these individuals, this must take place before 9-10 years of age in order to take advantage of the "critical period" of development. However, Robert Hess, director of vision research at McGill University, was part of a research team in 2013 which disproved this myth by confirming plasticity in the human visual brain at nearly any age.  Also by Hess et al. in 2013, direct evidence was gathered showing that suppression prevents the amblyopic eye/brain from learning to gather and process visual information and that treatment with lenses, occlusion and active vision therapy can improve visual acuity and binocular function at any age. Additionally, results from the Pediatric Eye Disease Investigator Group study (PEDIG) show that in patients aged 7-17 years, decreasing patching from full time to part time (2-6 hours daily) leads to a 53% increase in response to amblyopia treatment. Our team at HVTC has successfully treated adult amblyopes, including a gentleman in his 90s. 
The traditional form of monocular treatment does show some improvement in acuity in the amblyopic eye, however these visual gains have been shown to decrease in some patients once the patching schedule ends. Additionally, monocular patching teaches the child to be "one-eyed" since it does not address the lack of binocular vision development which created the amblyopia in the first place - the eyes have not been allowed to "play together" and thus do not develop as a team. Subsequently, there will be no improvement in depth perception, and the patient will inevitably be left "stereo blind" despite undergoing patching therapy for months, to sometimes years.
In addition to not resolving the underlying cause of the amblyopia, as well as not creating lasting acuity and/or depth perception improvements, traditional occlusion therapy has a significant impact on the child's family and social life, activities, and feelings and behaviours. A 2011 systematic review of studies examining amblyopia and its effects on quality of life found some of the following implications of amblyopia and/or occlusion therapy:
Family Life
  • Increased stress and anxiety for the parent.
  • Negative impact on parent-child and sibling-child relationships.
Social Interactions
  • Bullying from peers.
  • Feeling isolated from peers.
Activities
  • Negative impact on career choice and educational attainments.
  • Negative impact on school activities (patching while at school).
  • Long term negative impact on adulthood career choices. 
Feelings and Behaviours
  • Low self-esteem and negative self-image.
  • Depression.
  • Frustration.
  • Embarrassment.
Another 2011 research review looked at how amblyopia affects real-world visuomotor tasks. From eye-hand coordination deficits in movement, speed and accuracy (even upon conclusion of a patching program, due to the lack of improvement in binocular function), to an increased risk of tripping and colliding with obstacles/barriers while walking and driving, and reduced reading speed due to continued suppression of the amblyopic eye after patching, amblyopes suffer from the complex visual problems associated with the condition on a daily basis. The review concluded, "Amblyopes show a range of visuomotor impairments with the affected eye alone, but also in the binocular mode the amblyope is slower and less accurate than normally sighted individuals."
Developmental optometrists are using the principles laid out in more recent research to treat the underlying binocular vision disorder instead of simplifying this complex disorder down to a problem of acuity in one eye. The goals for a patient in an amblyopia vision therapy program include working the whole body and brain to restore as much as possible the eyesight or acuity in the amblyopic eye as well as to improve depth perception so that the individual has the opportunity to become truly binocular. 
This is not to say that patching has no role in the treatment of amblyopia by developmental optometrists - occlusion therapy is used in specific, supervised instances during vision therapy activities that require only minutes of time. The new approach to amblyopia treatment begins by addressing binocular vision development in conjunction with perceptual, visual processing and oculomotor therapy - it is an active process of the body and mind, requiring full participation by the patient.  
Developmental optometrists are making a difference in the lives of those affected by amblyopia - children and adults alike - by treating the condition with a new methodology that is rooted in neuroscience. By treating amblyopia as the binocular vision problem it is, patients are spared the frustration and emotion often associated with an outdated model of treatment, and can be guided with vision therapy to regain their binocularity.  
 
 
A BIG congratulations to all of the PVTAP (Practical Vision Therapy Accredited Program) participants who successfully passed the written component of their final examination! These therapists have been working very hard this year on learning the ins and outs of providing gold-standard office-based vision therapy to their patients. Throughout the course, therapists were taught relevant theory and had lots of hands-on experience learning and practicing many different therapy techniques. The participants will be taking their oral examinations at COVT&R's annual general meeting in August. We are all rooting for you! 
And another BIG congratulations to our vision therapist Pia and her husband Mike who welcomed their beautiful baby boy into the world on June 25. John Elijah came just a little bit early (and on his daddy's birthday too!). All of the staff and doctors send you warm hugs and congratulations. We are glad we were able to shower you with love just a week before Elijah was born!
Copyright © 2017 Halton Vision Therapy Center, All rights reserved.


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