Abstract
Purpose: To evaluate the precision of individual and combined macula and optic disc volumetric analysis, and the agreement between these two scan modes with spectral domain optical coherence tomography (OCT).Methods: Macular and optic disc volumetric measurements were performed with individual and combined scan protocols in one eye of 75 healthy subjects. Three repeated measurements were performed with each protocol. From the macular area, retinal thickness in nine different sectors and ganglion cell complex thickness in eight different sectors were analyzed from both scan modes. From the optic disc area, the peripapillary retinal nerve fiber layer (pRNFL) thickness in 12 clock sectors and the optic disc parameters were evaluated. For all the parameters, repeatability limit and agreement analysis were performed.Results: For the retinal thickness measurements in macula, the combined scan had two to three times larger repeatability limit than the individual scan for all the sectors except the central sector, where the repeatability limit was five times larger. The limits of agreement intervals were lower than 20 μm for all sectors, except the central. The ganglion cell complex measurements also had larger repeatability limits for the combined scans, and the limits of agreement intervals were <10 μm for all sectors. For the pRNFL thickness, the repeatability values were distributed like a vertically elongated ellipse for both scans, but still the repeatability was better for individual scan compared to the combined scan. The shortest and widest interval are obtained for sectors 9 (9 μm) and 12 (40 μm), respectively. The repeatability limit was <0.15 units for all disc parameters with both scan modes.Conclusion: The individual macula and optic disc scans had better repeatability than the combined scan mode, and the two scan modes cannot be used interchangeability due to the wide limits of agreement.
Highlights
Optical coherence tomography (OCT) is an irreplaceable imaging technology that allows the acquisition of in vivo and non-invasive cross-sectional images of the retina and choroid [1, 2]
Current-generation OCTs allow wide-field visualization of the retina with a scan area that can cover both macula and optic disc [18,19,20]
In the previous studies mentioned, the thickness parameters obtained with the wide-field scanning protocol from the swept-source OCT were compared to the individual scanning protocol obtained with the spectral domain OCT
Summary
Optical coherence tomography (OCT) is an irreplaceable imaging technology that allows the acquisition of in vivo and non-invasive cross-sectional images of the retina and choroid [1, 2]. Current-generation OCTs allow wide-field visualization of the retina with a scan area that can cover both macula and optic disc [18,19,20]. The wide-field scan protocol has been shown to be comparable and has a diagnostic ability that is similar to that of the individual macula and optic disc scans [19, 20]. In the previous studies mentioned, the thickness parameters obtained with the wide-field scanning protocol from the swept-source OCT were compared to the individual scanning protocol obtained with the spectral domain OCT. The Canon OCT HS-100 (Canon Europe, the Netherlands), which is a spectral domain OCT, has an updated scanning protocol that performs volumetric measurements on an area of 13 × 10 mm, allowing simultaneous imaging and combined volumetric analysis of both macula and optic disc. It would be interesting to know the precision and how comparable are the thickness values obtained with individual and simultaneous scanning protocols
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