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Nathaniel P Miller, Tapan Gandhi, Pawan Sinha, Bas Rokers; White-Matter Plasticity Following Sight-Restoration in Congenitally Blind Patients. Journal of Vision 2019;19(10):277d. doi: https://doi.org/10.1167/19.10.277d.
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In the developing world congenital cataracts are a major cause of visual impairment. While treatable, poor access to care means that many infants grow up effectively blind. Project Prakash, a humanitarian and scientific initiative based in India, has shown that congenitally blind children who receive cataract surgery in late childhood and adolescence can recover significant visual function. Here we evaluated the neuroanatomical basis for sight-restoration in these patients and its relationship to critical periods of human visual development. We assessed longitudinal white-matter changes in 10 congenital cataract patients (aged 12.6 ± 3.47 years) and 4 socioeconomically-matched controls (aged 16.5 ± 5.92 years) using diffusion weighted imaging (dMRI) tractography. Patients were screened and treated under the purview of Project Prakash (Delhi, India) and received bilateral cataract surgery with intraocular lens implantation. To track postoperative changes in white-matter structure, 1–6 longitudinal dMRI scans (AP phase-encoding, 40-directions, b=1000, 2 mm slices) were acquired for each participant. We assessed the structural integrity of 10 visual and non-visual pathways, measuring changes in mean diffusivity (MD) and fractional anisotropy (FA). We evaluated the effects of age, post-op time, and group (patient/control) on white-matter integrity with linear mixed effects models. Consistent with neural maturation, we found age-related changes in white-matter properties in most pathways. Evaluating structural changes specific to sight-restoration, we found little impact in early visual pathways (optic tract) and most non-visual pathways (both MD and FA FDR>0.05). However, significant effects of cataract surgery were observed in the optic radiation (FA, FDR=0.042), callosum forceps major (MD, FDR=0.015), and cingulum cingulate (MD, FDR=0.021). Critically, the nature of these changes in optic radiation and callosum forceps major depended on age. In summary, our results indicate that while sight-restoration has little effect on early visual pathways, it does lead to white-matter changes in specific later visual and visuo-motor pathways.
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