A morphological study of amblyopic eyes in children failing to achieve normal visual acuity after electronically monitored long-term occlusion treatment

Imaging Amblyopia: Insights from Optical Coherence Tomography (OCT)

Amblyopia refers to visual impairment resulting from perturbations in visual experience during visual development, typically secondary to strabismus, uncorrected refractive error, and/or deprivation. Amblyopia has traditionally been considered a cortical disease, but the depth of our understanding of this complex neurodevelopmental condition is limited by our ability to appreciate structural pathophysiology in the visual pathway. Recent advances in Optical Coherence Tomography (OCT) have facilitated numerous studies of the structural changes in the retina and optic nerve, thereby expanding our appreciation for the pathogenesis of this condition. In this review, we summarize findings from studies evaluating retinal, retinal nerve fiber layer, and choroidal thickness changes in patients with amblyopia. Focusing on the largest and most recent studies, we discuss common limitations and confounding variables in these studies. We summarize recent advances in ocular imaging technology and reconcile the findings of early histological reports with those of structural OCT in amblyopia.

[Occlusion treatment for amblyopia. Age dependence and dose-response relationship]

BACKGROUND

Based on clinical experience and studies on animal models the age of 6-7 years was regarded as the limit for treatment of amblyopia, although functional improvement was also occasionally reported in older patients. New technical developments as well as insights from clinical studies and the neurosciences have attracted considerable attention to this topic.

OBJECTIVE

Various aspects of the age dependence of amblyopia treatment are discussed in this article, e. g. prescription, electronic monitoring of occlusion dosage, calculation of indicators for age-dependent plasticity of the visual system, and novel, alternative treatment approaches.

METHODS

Besides a discussion of the recent literature, results of studies by our "Child Vision Research Unit" in Frankfurt are presented: results of a questionnaire about prescription habits concerning age limits of patching, electronic recording of occlusion in patients beyond the conventional treatment age, calculation of dose-response function and efficiency of patching and their age dependence.

RESULTS

The results of the questionnaire illustrate the uncertainty about age limits of prescription with significant deviations from the guideline of the German Ophthalmological Society (DOG). Electronic recording of occlusion allowed the quantification of declining dose-response function and treatment efficiency between 5 and 16 years of age. Reports about successful treatment with conventional and novel methods in adults are at variance with the notion of a rigid adult visual system lacking plasticity.

CONCLUSION

Electronic recording of patching allowed new insights into the age-dependent susceptibility of the visual system and contributes to a more evidence-based treatment of amblyopia. Alternative approaches for adults challenge established notions about age limits of amblyopia therapy. Further studies comparing different treatment options are urgently needed.