Dissertation > Medicine, health > Ophthalmology > Ocular adnexal organ disease > Ocular disease and strabismus > Amblyopia

The Researches of Deficit Mechanism of Motion Gratings Perception in Anisometropia and the Mechanisms of First-and Second-order Motion Detection in Normal Visual System

Author ChouZhuPing
Tutor ZhouYiFeng
School University of Science and Technology of China
Course Biophysics
Keywords anisometropic amblyopia contrast sensitivity perceptual learning first-order motion second-order motion
CLC R777.44
Type PhD thesis
Year 2007
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Amblyopia is one of the most common visual impairment and the condition affects approximately 2 to 3 out of every 100 persons in our country. Amblyopia is a developmental visual disorder that is usually defined as a deficit in optotype acuity without obvious structural or pathological ocular anomalies. The neural correlates underlying amblyopia are still unclear though it has been widely accepted that amblyopia develops as a result of abnormal visual experience during "sensitive period". Investigating the mechanisms of amblyopia will help the understanding of several related visual functions in normal visual system and benefit to the clinic treatment. The first part of the experiments focused on the deficit in perceiving moving grating detection and direction discrimination in adult anisometropic amblyopia. Our results suggest the deficit of spatio-temporal processing mainly depend on the loss of spatial vision in anisometropic amblyopia. For five anisometropic amblyopes and five normal controls, contrast sensitivities in both grating motion direction discrimination and moving grating detection were measured with the same moving sinewave stimuli over a wide range of spatial and temporal frequencies. We found that the grating motion direction discrimination deficits in anisometropic amblyopia can be almost completely accounted for by deficits in moving grating detection. Furthermore, the differences between the amblyopic and amblyopes’ non-amblyopic eyes are non-specific to temporal frequency in both motion direction discrimination and moving grating detection, and are quantitatively identical to the differences in their contrast sensitivities(the performance of the amblyopes’ non-amblyopic eyes have no significant difference from those of the normal eyes in the three tasks we used). Complementing an earlier study on strabismic amblyopia (Hess & Anderson, 1993), these results suggest that local motion sensitive mechanisms are largely intact in anisometropic amblyopia; the apparent local motion deficits in anisometropic amblyopia can be modeled with deficits in contrast sensitivity functions. The result may have major therapeutic implications, i.e., any procedure that improves contrast sensitivity would lead to improvements in motion perception in anisometropic amblyopia.Most of the early psychophysical researches in visual science focused on spatial vision. Recently, the processing of moving stimuli, especially the mechanisms of first- and second-order motion have been one of the most popular questions in visual science. In the second part, we work on the mechanisms for perceiving first- and second-order motion in normal vision system. Previous reports have confused views on one or two channels used in first- and second-order motion processing. To clarify the mechanisms in first- and second-order motion perception processing, we used sine-wave first- and second-order motion gratings and motion direction discrimination tasks in parafovea, and compared the contrast sensitivities of motion direction discrimination before and after training. Our results showed the first-order motion training only improved the performance in first-order motion direction discrimination tasks, while the second-order motion training improved the performance of both first- and second-order motion direction discrimination tasks. These results suggested there are partly separated mechanisms in perceiving first- and second-order motion.

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