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Alekya Rajanala, M Ali Shariati, Yaping Joyce Liao; Long Distance Homonymous Hemi-Macular Retrograde Degeneration of the Visual Pathway: A Comparison of Anterior and Posterior Visual Pathway Lesions. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5861.
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© ARVO (1962-2015); The Authors (2016-present)
Trans-synaptic degeneration of the visual pathway following ablation of the striate cortex is well established in non-human primates and involves parvocellular retino-geniculate connections. In humans, trans-synaptic degeneration is more controversial but has been described recently. In this study, we used optical coherence tomography (OCT) to examine the severity and timing of retrograde degeneration in human visual pathway lesions.
We performed a retrospective chart review of patients with homonymous visual field loss and confirm lesions of the visual pathway on brain imaging studies. Patients were categorized by location of brain lesion. We analyzed over 70 high quality OCT studies and correlated the findings with visual field loss and MRI.
We studied the changes in macular ganglion cell complex in 15 patients with anterior and 20 patients with posterior visual pathway lesions. There was significant hemi-macular thinning of the ganglion cell complex (GCL+IPL) in patients with anterior (abnormal: 56.2±2.5 µm, normal: 78.2±1.5 µm, N=15, P<0.0001) and posterior (abnormal: 63.6±2.3 µm, normal: 71.7±2.6 µm, N=19, P=0.01, Mann-Whitney). At one year after onset, anterior lesions led to significantly more severe GCC thinning than posterior lesions (anterior: 59.2±2.9 µm, N=10; posterior: 67.8±2.8 µm, N=6; P=0.03). At two years after onset, the rate of thinning of the anterior lesions was significantly faster and more than three times that of the posterior lesions (anterior: 4.6±1.0 µm/month, posterior: 1.2±1.1 µm/month; P=0.05). Patients with congenital or incidentally noted homonymous hemifield defects often exhibited significant hemi-macular thinning, presumably because the thinning has had years to develop. Correlation between the pattern of retinal thinning and that of visual field loss indicated that a decrease of 1 dB in visual field sensitivity predicts a decrease of 0.1543 µm in GCC thickness.
Retrograde, homonymous, hemi-macular thinning occurred in the human visual pathway over long distance, even trans-synaptically. There was more rapid and more severe thinning in anterior visual pathway lesions (optic tract, LGN) compared with that of occipital lobe lesions. Further investigation of trans-synaptic degeneration can assist regeneration therapy and efforts to restore patient vision.
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