Open Access

Claudia Bäumer

• Amblyopia is a developmental disorder of the visual system that leads to reduced vision in one or both eyes. People suffering from amblyopia show different perceptual deficits like reduced contrast sensitivity, reduced or no stereopsis, spatial uncertainty, and spatial and temporal distortions when viewing with the amblyopic eye. In the following thesis, different psychophysical methods are used to investigate anomalous perception of amblyopic participants in detail with the main focus on the perception of temporal instability. In the qualitative experimental paradigms it is shown that temporal instability is mainly perceived by strabismic and strabismic-anisometropic amblyopes. The temporal deficits occur only at spatial frequencies higher than 1.6 c/deg, and are perceived in addition to the spatial distortions. Illusory colours sometimes accompany the temporal distortions. There seems to be a relationship between crossed hand and eye dominance and the perception of temporal instability. In the quantitative experiments it is shown that temporal instability in amblyopic perception has a negative impact on the performance in psychophysical tasks. Amblyopes perceiving temporal instability show enhanced spatial uncertainty and spatial distortions for different types of stimulus presentation (auditive vs. visual) when compared to amblyopes without temporal instability. This might be due to deficits in auditive-visual mapping. These deficits in auditory-to-visual mapping suggest an impairment of the dorsal “where” pathway. Thus, it might be that amblyopes with temporal distortions have deficits in the dorsal pathway that come up in addition to the known deficits of the ventral “what” pathway and are related to the perception of temporal instability. The different results of the experiments found in this thesis seem to confirm this hypothesis. Studies using functional imaging techniques might be appropriate for a further investigation of amblyopic deficits involving the dorsal pathway.