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S. S. Choi, R. J. Zawadzki, J. S. Werner; Applications of Adaptive Optics - OCT: Visual Sensitivity Correlated With Morphological Changes in Retinal and Optic Nerve Diseases as Revealed by Retinal Thickness Maps. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1058.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive optics - OCT (AO-OCT) provides retinal images sampled with 25 times higher density per unit area than Fourier-domain (Fd) OCT. This permits localized volumetric imaging with greater fidelity in identifying retinal layers for segmentation. The goals of this study were (1) to evaluate AO-OCT inner and outer retinal layer thickness maps in diseased retinas, (2) to compare them with visual function at the corresponding retinal locations, and (3) to test if these retinal thickness maps can detect retinal changes that have been missed by conventional clinical functional tests.
Twenty patients with various types of retinal and optic nerve diseases including retinal dystrophy, maculopathy, optic neuropathy and glaucoma were imaged with ultrahigh resolution AO-OCT (3.5 µm in all three dimensions) and high resolution Fd-OCT (4.5 µm axial and ~15 µm lateral resolution) instruments developed in our laboratory. Retinal locations were chosen based on functional test results so that both affected and unaffected retinal areas could be imaged and compared. Functional tests included visual field maps and mfERG. Three-dimensional AO-OCT image volumes were segmented into inner retinal layer [nerve fiber layer (NFL) + ganglion cell layer (GCL) + inner plexiform layer (IPL)] and outer retinal layer [layers from external limiting membrane (ELM) to retinal pigment epithelium (RPE)] using custom volume rendering and segmentation software.
Retinal and optic nerve disease patients showed significantly thinner outer and inner retinal layers respectively at the retinal locations showing reduced visual performance. The more severe the disease, the thinner the layers became. In retinal disease patients, the outer retinal layer thickness became normal at unaffected areas, however, in optic nerve disease patients, the inner retinal layer remained thinner than normal in unaffected areas as revealed by normal visual sensitivity from visual field testing. This finding suggests that AO-OCT inner retinal layer thickness maps are able to show thinning of retina in patients with optic nerve diseases even before manifestation of vision loss.
This study demonstrated that AO-OCT retinal thickness maps provide a reliable measure correlated with visual function in both retinal and optic nerve disease patients. Furthermore, it may also be more sensitive than visual field analysis in assessing integrity of the inner retinal layer of optic nerve disease patients.
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