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T. Buehren, M. Durbin, G. Kunath-Fandrei, M. Whitby, S. Meyer; Retinal Layer Segmentation and Interpretation Using High-Definition Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1881.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate performance of retinal layer segmentation using CirrusTM HD-OCT. To compare CirrusTM HD-OCT retinal subfield thickness measurements to those of standard OCT.
24 subjects with healthy eyes, mean age 41.8 years (range 21 to 58 years) were recruited for the study. For all subjects, 6x6 mm macular cube scans (200x200 i.e. total of 40000 A-scans) for quantitative segmentation analysis were collected using the CirrusTM HD-OCT (Carl Zeiss Meditec Inc.). 6x6 mm macular cube scans(512x128 i.e. total of 65536 A-scans) and 6 mm Raster Scans (5 lines with each 4096 A-scans) for qualitative separation of retinal layers were collected for a subset of subjects. Automatic segmentation of inner limiting membrane (ILM) and retinal pigment epithelium (RPE) as well as 3-D reconstructions of total retinal thickness maps, ILM HD-layer maps and RPE HD-layer maps were performed.
Generally, three distinct layers within the highly reflective band below the neuro-sensory retina could be discerned in the high resolution cross sectional B-scans. CirrusTM HD-OCT’s segmentation algorithms (200x200 & 512x128 cube scans) detected the RPE at the upper edge of the third layer of the three distinct layers within the highly reflective band for most of our subjects. The ILM was detected along the interface of inner retina and vitreous body. Mean 1 mm central subfield thickness (ILM - RPE) based on this segmentation was 263.2 microns (range 230 - 312) which was 59.8 microns above the mean and 24.2 microns above the 95 percentile of the age matched central subfield thickness of the Stratus normative database (range 168 - 239 microns). Peripheral sub-field sectors (3 mm and 6 mm) also showed increased values compared with Stratus normative retinal thickness.
The CirrusTM HD-OCT, which uses the outer highly reflective band as reference point for the RPE, results in increased thickness measurements compared with standard resolution OCT. Increased resolution in optical coherence tomography provides new insights into retinal layer separation but also opens up new questions regarding interpretation and standardization of gained information. General agreement and establishment of a new gold standard of retinal layer interpretation based on high- and ultra-high-resolution OCT is yet to be accomplished.
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