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Sarim Mohammad, Irene Gottlob, Robert A Dineen, Viral Sheth, Frank A Proudlock, University of Leicester; Comparison of Retinal and Optic Nerve Head Structure in Albinism Imaged Using OCT with the Post Orbital Visual Pathway Imaged using MRI. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5100.
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OCT allows the quantification of optic nerve head (ONH), retinal nerve fibre layer (RNFL) and macular abnormalities in albinism with a high degree of objectivity. However, it is unclear whether these measures relate to visual pathway abnormalities posterior to the eye. We have compared retinal abnormalities to chiasmal and cortical abnormalities quantified using magnetic resonance imaging (MRI).
OCT: Macular and optic nerve scans were acquired using, a high-resolution SD-OCT device (SOCT Copernicus HR, OPTOPOL Technology S.A.). ImageJ (http://rsbweb.nih.gov/ij/) was used to correct nystagmus associated motion artefacts through alignment of ONH and retinal vascular contours and measure retinal layer thickness. SOCT Copernicus Software (version 4.2) was used calculate the cup, disc and rim dimensions and measure the peripapillary RNFL thickness. MRI: 23 patients underwent 3T MRI (Philips Achieva) using a 3-dimensional magnetization-prepared rapid gradient-echo sequence. Cerebral cortical thickness was derived using Freesurfer software (http://surfer.nmr.mgh.harvard.edu) with automated cortical parcellation. Cortical thickness values for the occipital pole region-of-interest (ROI) were used in the statistical analysis. ROIs for the optic nerves, tracts and chiasm were drawn manually using ImageJ.
The temporal peripapillary RNFL thickness was related to the ipsilateral optic nerve areas (p<0.001, r=0.608) and contralateral optic tract areas(p<0.001, r=0.608). The optic tracts also related significantly with contralateral disc and cup areas while both optic nerves and tracts correlated to retinal pigment epithelium thickness at the fovea (p<0.05). The chiasm area was significantly correlated with the averaged cup area of both eyes (p<0.05, r=0.414). The occipital pole cortical thickness was significantly correlated to the disc area (p<0.05, r=0.493) and rim volume (p<0.05, r=0.429).
Using a combination of OCT and MRI, we have been able to investigate the relationship between various retinal, optic nerve, chiasmal and cortical abnormalities found in albinism. This will help further our understanding of the visual deficits in patients with albinism and aid their optimal management.
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