Abstract
Abstract: :
Purpose: Visual deficits in amblyopia are commonly defined by low–level losses in spatial resolution and contrast sensitivity. However, it has become increasingly apparent in recent years that the extent of the deficit can depend on the visual function measured; losses in the accuracy of spatial localisation are uncorrelated with contrast or acuity loss. It is also widely assumed that intervention treats the whole condition and that all aspects of visual function are equally affected. The purpose of the study was to establish which visual functions are most amenable to therapy. Methods: 20 amblyopic children with a mean age of 6.2±1.3years were recruited. These patients had not received treatment previously and provided the rare opportunity to investigate the condition prior to and during occlusion therapy. In addition to routine orthoptic and optometric evaluation, resolution, contrast detection and spatial alignment thresholds were measured psychophysically. These measures were repeated in both the amblyopic and non–amblyopic eye as the children underwent a prescribed occlusion therapy regime, following parental consent. Results: All amblyopes demonstrated a functional loss in each of the tests used. With the exception of the spatial alignment thresholds, occlusion therapy appeared to improve all other aspects of amblyopic visual function with a significant difference in pre– and post–therapy results. There was no improvement in sensitivity to spatial position during occlusion and in the majority of amblyopes alignment deficits were scale invariant. Conclusions: The well–established resolution and contrast sensitivity deficits in amblyopia showed concurrent improvement with traditional acuity measures during occlusion therapy. However, spatial alignment performance demonstrated no such improvement. In the same way that different visual functions have different developmental periods it appears that the recovery of visual function, that accompanies occlusion therapy is itself task specific.
Keywords: amblyopia • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials • perception