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Spectral- and time-domain optical coherence tomography measurements of macular thickness in normal eyes and in eyes with diabetic macular edema.

ABSTRACT: To report macular thickness values in normal eyes and eyes with diabetic macular edema (DME) using time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT), and to derive a conversion equation.The index study was a prospective investigation conducted on 80 eyes from 40 normal subjects and 130 eyes from 118 patients with DME seen in our clinic. Retinal thickness values from the central 1 mm of the macula and surrounding four ETDRS subfields were acquired using TD-OCT (Stratus OCT) and SD-OCT (SPECTRALIS HRA+OCT). Measurements of the central (C) subfield from both devices were used to derive a conversion equation. The equation was used to predict SD-OCT values using measurements from TD-OCT. Agreement between predicted and actual SD-OCT measurements was assessed.In normal eyes, the mean difference between TD-OCT and SD-OCT measurements of the C subfield was 76 μm (CI(95)=74 and 77, respectively). The conversion equation, y=1.029x+72.49, was derived. In eyes with DME, using the equation, SPECTRALIS-predicted values were 5% higher than actual measurements, with 95% of predicted values falling within 9% of the actual measurements. Relocating SD-OCT grids to match the location on TD-OCT resulted in predicted values falling within 7% of actual measurements.The percent difference between actual thickness measurements from SPECTRALIS and predicted thickness measurements, using the conversion equation, was within reported limits of repeatability of Stratus in eyes with DME. Our equation may help correlate OCT values from both devices in standard care and clinical trials for DME.

SUBMITTER: Ibrahim MA

PROVIDER: S-EPMC3298977 | biostudies-other | 2012 Mar

REPOSITORIES: biostudies-other

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Project description:Understanding measurement variability and relationships between measurements obtained on different optical coherence tomography (OCT) machines is critical for clinical trials and clinical settings.To evaluate the reproducibility of retinal thickness measurements from OCT images obtained by time-domain (TD) (Stratus; Carl Zeiss Meditec) and spectral-domain (SD) (Cirrus; Carl Zeiss Meditec, and Spectralis; Heidelberg Engineering) instruments and formulate equations to convert retinal thickness measurements from SD-OCT to equivalent values on TD-OCT.A cross-sectional observational study was conducted in private and institutional practices. Persons with diabetes mellitus who had at least 1 eye with central-involved diabetic macular edema, defined as Stratus central subfield thickness (CST) of 250 ?m or greater, participated. An additional normative cohort (individuals with diabetes but without diabetic macular edema) was enrolled. Each study eye underwent 2 replicate Stratus scans followed by 2 replicate Cirrus or Spectralis scans (real-time image registration used) centered on the fovea.Optical coherence tomography CST and macular volume.The Bland-Altman coefficient of repeatability for relative change in CST (the degree of change that could be expected from measurement variability) was lower with Spectralis (7%) compared with Cirrus (14%) and Stratus (12% and 15% within Cirrus/Stratus and Spectralis/Stratus groups, respectively). For each cohort, the initial Stratus CST was within 10% of the replicate Stratus measurement nearly all of the time; the conversion equations predicted a Stratus CST within 10% of the observed thickness 86% and 89% of the time for Cirrus/Stratus and Spectralis/Stratus groups, respectively, which is similar to the agreement on Stratus test-retest. The Bland-Altman limits of agreement for relative change in CST between machines (the degree of change that could be expected from measurement variability [combining within and between instrument variability]) were 21% for Cirrus and 19% for Spectralis when comparing predicted vs actual Stratus measurement.Reproducibility appears to be better with Spectralis than with Cirrus and Stratus. Conversion equations to transform Cirrus or Spectralis measurements to Stratus-equivalent values, within 10% of the observed Stratus thickness values, appear feasible. Central subfield thickness changes beyond 10% when using the same machine or 20% when switching machines, after conversion to Stratus equivalents, are likely due to a change in retinal thickness rather than measurement error.

Project description:PurposeTo compare intra-retinal layer thickness measurements between eyes with no or mild diabetic retinopathy (DR) and age-matched controls using Spectralis spectral-domain optical coherence tomography (SD-OCT).MethodsCross-sectional observational analysis study. High-resolution macular volume scans (30° * 25°) were obtained for 133 type 2 diabetes mellitus (T2DM) patients with no DR, 42 T2DM patients with mild DR and 115 healthy controls. The mean thickness was measured in all 9 Early Treatment Diabetic Retinopathy Study (ETDRS) sectors for 8 separate layers, inner retinal layer (IRL), outer retinal layer (ORL) and total retina (TR), after automated segmentation. The ETDRS grid consisted of three concentric circles of 1-, 3-, and 6-mm diameter. The superior, inferior, temporal, and nasal sectors of the 3- and 6-mm circles were respectively designated as S3, I3, T3, and N3 and S6, I6, T6, and N6. Linear regression analyses were conducted to evaluate the associations between the intra-retinal layer thicknesses, age, diabetes duration, fasting blood glucose and HbA1c.ResultsThe mean age and duration of T2DM were 61.1 and 13.7 years, respectively. Although no significant differences in the average TR and ORL volumes were observed among the groups, significant differences were found in the volume and sectorial thicknesses of the inner plexiform layer (IPL), outer plexiform layer (OPL) and IRL among the groups. In particular, the thicknesses of the IPL (S3, T3, S6, I6 and T6 sectors) and the IRL (S6 sector) were decreased in the no-DR group compared with the controls (P < 0.05). The thickness of the OPL (S3, N3, S6 and N6 sectors) was thinner in the no-DR group than in mild DR (P < 0.05). The average IPL thickness was significantly negatively correlated with age and the duration of diabetes.ConclusionThe assessment of the intra-retinal layer thickness showed a significant decrease in the IPL and IRL thicknesses in Chinese adults with T2DM, even in the absence of visible microvascular signs of DR.

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Spectral- and time-domain optical coherence tomography measurements of macular thickness in normal eyes and in eyes with diabetic macular edema.

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