Abstract
PurposeTo evaluate the repeatability of the new spectral domain optical coherence tomography (HOCT-1F), and also to evaluate the agreement between vertical and horizontal scan protocols. In addition, we also evaluated the relation between the repeatability and age.MethodsThree consecutive measurements of the inner limiting membrane–retinal pigment epithelium (ILM-RPE), inner limiting membrane–inner plexiform layer (ILM-IPL) from macular horizontal and vertical scans, and inner limiting membrane–retinal nerve fiber layer (ILM-RNFL) from optic disc horizontal scan. 159 subjects were included in the analysis. The within subject standard deviation (Sw) and the repeatability limits (Rlimit) are used to represent the repeatability of the parameters for the different sectors.ResultsThe Sw for the ILM-RPE thickness was less than 3.5 μm for each sector and scan direction. The Sw values varied within the sectors and scan modes, with horizontal scan modes resulting in better values for the horizontal sectors, and vice versa. The Sw for the GCL-IPL thickness was less than 2 μm, and was similar between the vertical and horizontal scan modes for each sector map. For the optic disc scan, the Sw was not symmetric along the clock-hour map sectors, the largest Sw values were seen in the vertical sectors (8.6 μm). The mean difference between the vertical and horizontal scans was less than 2 μm for each retinal thickness sector map. Significant but weak correlation between the Sw and the subject’s age was seen in both macular and optic disc scans.ConclusionsThe repeatability of the HOCT-1F to measure the ILM-RPE-, ILM-IPL- and ILM-RNFL-thickness is good. The repeatability of the ILM-RPE thickness is dependent on the scan direction, which should be taken into account when calculating retinal thickness. There is a weak correlation between the repeatability and the subject’s age.
Highlights
Optical coherence tomography (OCT) has an irreplaceable role in the field of ophthalmology
Three consecutive measurements of the inner limiting membrane–retinal pigment epithelium (ILM-RPE), inner limiting membrane–inner plexiform layer (ILM-IPL) from macular horizontal and vertical scans, and inner limiting membrane–retinal nerve fiber layer (ILM-RNFL) from optic disc horizontal scan. 159 subjects were included in the analysis
The Sw for the ILM-RPE thickness was less than 3.5 μm for each sector and scan direction
Summary
Optical coherence tomography (OCT) has an irreplaceable role in the field of ophthalmology. Both clinicians and researchers use OCT to envisage and understand retinal and choroidal pathologies[1,2,3]. The segmentation provides useful quantitative information about each individual layer of the retina. In order to know how consistent the quantitative measurements of the retinal layers are, it is important to assess the repeatability of the measurements. The repeatability of the measurement is dependent on scan resolution, acquisition time, segmentation algorithm and the retinal condition[9,10,11,12,13]. Current generation OCT instruments provide better resolution, faster measurements and better segmentation algorithms which in turn provides us with reliable quantitative data. The three-dimensional scan can be performed with various scan resolutions and with both vertical and horizontal scan lines, both with auto- and semi-auto scanning protocols
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