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Editors Selection IGR 8-3
Optical Coherence Tomography: Longitudinal change ONH and PPA by SD-OCT
Comment by Linda Zangwill on:
27761 Longitudinal change detected by spectral domain optical coherence tomography in the optic nerve head and peripapillary retina in experimental glaucoma, Strouthidis NG; Fortune B; Yang H et al., Investigative Ophthalmology and Visual Science, 2011; 52: 1206-1219
In this important paper, Strouthidis et al. (192) clearly demonstrate for the first time that longitudinal spectral domain optical coherence tomography (SDOCT) imaging using dense radial scanning of the optic nerve head (ONH) can detect deep optic nerve head changes in the laminar and pre-laminar regions in experimental glaucoma eyes of non-human primates. In addition, the investigators found that these changes are present at the onset of HRT-detected optic nerve head surface height depression that the authors suggest may reflect 'conformational' changes in the neural and non-neuronal rim tissue. This study highlights an important potential advantage of SDOCT imaging ‐ that deep ONH changes are detectable at early stages of the disease, at least in this experimental monkey model. Using manual segmentation techniques, the authors elegantly show in a series of figures how the delineation of the retinal nerve fiber layer, Brunch's membrane/retinal pigment epithelium, neural canal opening (NCO) and anterior lamina cribrosa surface (ALCS) is completed, and how histological information was used in that process. Their results demonstrate that progressive glaucomatous changes include thinning of preliminary tissue, posterior displacement of the ALCS and NCO, and reduction in neuroretinal rim width and volume. Moreover, the authors show how the NCO can be used as a reference plane for SDOCT optic nerve head measurements. Despite posterior movement of the NCO relative to the more stable peripheral Bruch's membrane ( in these experimental glaucoma eyes), the authors argue convincingly that NCO may still be a reasonable reference plane for SDOCT measurements. The issue of the most appropriate reference plane for SDOCT measurements will be a topic of further investigation.
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