Abstract
Purpose
To compare macular thickness measurements obtained from time domain optical coherence tomography (TD-OCT) and 2 spectral domain (SD) OCTs and to evaluate their repeatability and agreement in normal subjects and diabetic macular edema patients.
Methods
Fifty-four healthy, normal subjects and 26 diabetic macular edema patients were participated in this study. In a randomly selected eye from each subject, two serial macular measurements were obtained from TD-OCT (Stratus OCT) and SD-OCTs (Cirrus HD-OCT, Spectralis HRA+OCT) by an experienced technician in random order. Nine areas of macular thickness map and repeatabilities obtained by the 3 OCTs were compared.
Results
In relative repeatability, SD-OCT showed better results overall compared to TD-OCT. Macular thickness was greatest in the Spectralis HRA+OCT in both normal subjects and diabetic macular edema patients, followed by Cirrus HD-OCT and Stratus OCT. In normal subjects, regardless of the type of comparison between the machines there was a statistically significant difference in all 9 areas.
Conclusions
While the TD-OCT and the 2 SD-OCTs are reliable for macular thickness measurement, SD-OCT has better measurement repeatability compared with TD-OCT. Because macular measurements obtained from the 3 OCT systems cannot be interchanged, an effort should be made to standardize the measurement of each system.
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Figure 1.
AREDS grid at right used for reporting retinal thickness (F=fovea; S1=superior inner;, N1=nasal inner; I1=inferior inner; T1=temporal inner; S2=superior outer; N2=nasal outer; I2: inferior outer; T2=temporal outer).
![jkos-50-1050f1.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f1.gif)
Figure 2.
Comparison of macular thickness among the three OCTs in nine areas (A=normal; B=diabetic macular edema) (F=fovea; S1=superior inner; N1= nasal inner; I1=inferior inner; T1=temporal inner; S2=superior outer; N2=nasal outer; I2=inferior outer; T2=temporal outer).
![jkos-50-1050f2.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f2.gif)
Figure 3.
Comparison of the three OCT's relative repeatability (%) (A=normal; B=diabetic macular edema) (F=fovea; S1=superior inner; N1=nasal inner; I1= inferior inner; T1=temporal inner; S2=superior outer; N2=nasal outer; I2=inferior outer; T2=temporal outer).
![jkos-50-1050f3.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f3.gif)
Figure 4.
Bland-Altman plots of the three OCTs. The mean difference is represented by the blue solid line and the 95% confidence limits, by the dotted lines (A=normal; B=diabetic macular edema).
![jkos-50-1050f4.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f4.gif)
Figure 5.
Illustration of how time domain and spectral domain OCT samples the retina differently (Right= SD-OCT; Left=TD-OCT).
![jkos-50-1050f5.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f5.gif)
Figure 6.
Tomographies of the macula taken by the three OCTs with reference lines. All three anterior lines are similar to the ILM, but each posterior line is situated differently.
![jkos-50-1050f6.tif](/upload/SynapseXML/0035jkos/thumb/jkos-50-1050f6.gif)
Table 1.!
Mean values and reliabilities of macular thickness parameter in Stratus OCT
Table 2.!
Mean values and reliabilities of macular thickness parameter in Cirrus HD-OCT
Table 3.!
Mean values and reliabilities of macular thickness parameter in Spectralis HRA+OCT
Table 4.
Mean and standard deviation of each OCT's macular thickness measurement difference. In the comparison of each OCT's macular thickness, all 9 areas showed a significant difference of p<0.001 (* paired t-test. all of them (9 areas))