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Dr. Sue Barry, PhD Both a researcher and an individual with Strabismus & Amblyopia
Below is a 'translation into common language" of a technical paper that reviewed literature on Amblyopia, commonly known as lazy eye, and then a review by Dr. Susan Barry, PhD, who is both a researcher, college professor, and an individual who had several surgeries as a young child to address her eye turn and lazy eye. As an adult, she had Vision Therapy and was then able to gain the ability to use her two eyes as a team and resolve both the amblyopia and the strabismus.
Amblyopia (lazy eye) is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experience early in life.
Amblyopia is clinically important because it is a major cause of vision loss in infants and young children.
Amblyopia is not a problem of the eye, but rather a brain based problem that is caused when someone does not have normal visual development. Yes, VISION DEVELOPS.
Undestanding Amblyopia and how it is "fixed" also helps us understand how changable the brain is, and how it can recover, for example, after a brain injury.
There are now much more effective ways of treating amblyopia than the old "patching" way that did not work, and still does not work. Why do some doctors still hold on to treatments that don't work?
Why do many doctors still think that after a certain "critical period" you cannot effectively treat amblyopia?
There are new clinical trials and new basic research studies that suggest othewise.
Difficulty in using the two eyes together as a team, and then the ability to judge depth (stereoscopic depth perception) is the most common problem associated with amblyopia.
Amblyopia has a substantial impact on visuomotor tasks, difficulties in playing sports in children and moving safely in older adults. Problems in using the two eyes together as a team and the ability to judge dept can also limit career choices for people who have amblyopes.
The ability to judge depth is greater in people who have a lazy eye due to an eye turn rather than those who have a lazy eye due to a large difference between the two eyes.
Various approaches have been used to treat amblyopia, including patching, perceptual learning, and videogames.
There are several promising new approaches to recovering stereopsis in both anisometropic and strabismic amblyopes.
Recovery of stereoacuity (the ability to judge depth) may require more active treatment in strabismic than in anisometropic (where there is a large difference between the two eyes) amblyopia.
Treating only one eye, when there is an eye turn, (for example, patching) is not likely to improve conditions.
The likelihood of permanent improvement is much greater when someone learns how to use the two eyes together (through vision therapy) and even better with direct stereo training.
This paper by Levi and colleagues challenges 2 assumptions that have persisted in the medical literature for the past 2 centuries. The first is that the principle deficit in amblyopia is reduced visual acuity in the affected eye so that the optimal treatment is occlusion of the non-amblyopic eye. However, current research suggests that amblyopia results from poor binocular cooperation between the 2 eyes, leading not only to reduced visual acuity in the affected eye but also to reduced or absent stereopsis. Accordingly, the authors reviewed the impact of amblyopia on stereopsis and the consequences of reduced or absent stereopsis on visuomotor skills, career opportunities, and self-image. Occlusion therapy, even if it results in enhanced visual acuity in the amblyopic eye, produces only modest improvements in stereopsis.
Treatment for amblyopia has traditionally been applied only to children because it was generally assumed that the visual system is malleable only during a critical period in early childhood. However, as the authors point out, a large degree of plasticity in the very young brain does not imply that plasticity comes to an end after childhood. Indeed, the authors review 21 experimental treatments involving 259 subjects, mostly adults. These studies involved monocular and dichoptic perceptual learning protocols, monocular and dichoptic videogame play, and direct stereo training. Across all treatments, 55% of anisometropic amblyopes and 26% of strabismic amblyopes showed substantial improvement in stereoacuity after training, with the dichoptic and direct stereo training protocols proving the most effective. In summary, Levi and colleagues provide evidence that amblyopia can be treated in adulthood. Limited recovery from amblyopia to date may result from the narrow scope of treatments standardly available and an overly pessimistic view of adult visual plasticity.