5 Years on

The title of this editorial makes reference to that previously published here in 2006¹ that introduced a series of amblyopia-related articles based on author presentations to an invited group of participants assembled under the auspices of the London-based Novartis Foundation. Now, in 2011, we are grateful once again to be given the opportunity to introduce a further series of articles arising out of contributions to the 1st City University Symposium* that recently reviewed progress in selected sub-fields of amblyopia research.

Casting our eyes over the subject matter and content of those articles published in 2006 and making comparison with those published in this issue allows us to gauge the depth and direction of progress that has occurred over the past 5 years. Two topics common to both the present and 2006 reviews are, not unsurprisingly, the neuroscientific underpinnings of amblyopia arising out of animal studies, and the treatment of children.

In the former case, Sengpiel here provides an overview of how experimental models of amblyopia have contributed to our understanding of the human condition focusing specifically on strategies that may prevent or reverse the effects of monocular deprivation. It is our experience that those working with animals often, and not without good reason, avoid extrapolating techniques and findings from the laboratory to human amblyopia specifically with regard to treatment. However, Sengpiel rightfully draws attention to how animal models of monocular deprivation can inform the practice of occlusion therapy with amblyopic children.

Where the treatment of human amblyopia is concerned, Stewart, Moseley, and Fielder focus their review on the abundance of clinical treatment trials conducted since 2006 (certainly exceeding the total number ever previously published) that have great potential to advance clinical practice. Progress highlighted includes the now firmly established benefits of refractive correction (optical treatment/refractive adaptation) as a therapy in its own right for all major subtypes of amblyopia and that atropine penalization appears to produce similar outcomes to the still more widely practiced occlusion therapy for those with moderate or severe amblyopia. Yet these authors observe that while trial outcomes have translated into practice guidelines, practitioner uptake and implementation of such knowledge is not universal. A subtopic not touched upon in the preceding 2006 review of treatment² was the role of education and family support in improving compliance with occlusion therapy, and given that we now more fully understand the relationship between visual outcomes and prescribed occlusion dose, this would seem an important advance.

Although by 2006, the potential of therapies other than mainstream penalization and occlusion had been demonstrated in the (psychophysics) laboratory,³ their implementation into routine clinical practice still appeared some way off. In 2011, Astle, McGraw, and Webb describe promising advances in what they term learning-based interventions among adult amblyopic observers (in whom it is now accepted retain sufficient neural plasticity that it may be manipulated). The effectiveness of this approach now appears to be on the cusp of emerging from the laboratory to await evaluation by randomized, controlled trial.

In a similar manner by which traditional views of neural plasticity are being overturned by findings such as those of Astle and colleagues, Hess, Mansouri, and Thompson describe an entirely new treatment modality underpinned by the notion that active suppression lies at the heart of the amblyopic deficit while cellular function remains intact. They further conjecture that contrary to the traditional view, which focuses on treatment of the monocular visual loss, it is the restoration of binocular function that should be prioritized. Demonstrating in the laboratory a technique for reducing interocular suppression, these authors proceed to describe its implementation using commercially available platforms. We await with anticipation the outcome of its use among clinically presenting amblyopic patients.

Last among the contributions to this issue is that of Grant and Moseley, who undertake a review of what must be the most under-researched subfield of amblyopia study: the functional or real-world consequences of possessing an amblyopic visual system. They review the performance of amblyopic subjects on everyday activities such as walking, driving, and reading, and on eye-hand coordination. They also re-examine the oft-debated issue of what precisely are the functional benefits of binocular over monocular vision, if any. A principal conclusion of these authors is that amblyopic observers lacking stereoacuity do demonstrate quantifiable deficits on real-world visuomotor tasks, particularly those that rely on stereo acuity and stereomotion processing.

It has been a privilege to act as guest editors for this issue of Strabismus. We would like to take this opportunity to thank all our contributors for their insightful and diverse accounts of current amblyopia research. It is our fervent hope that 5 years from now, many of the lab-based techniques for understanding and treating amblyopia described herein will have impacted upon, or become integrated into, our mainstream clinical practice.