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Oh, Moon, and Kim: Repeatability and Agreement of Macular Thickness Measurement Using Time and Spectral Domain OCT in Diabetic Macular Edema
Original Article

J Korean Ophthalmol Soc 2010;51(3):372-378.

Published online: 25 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.3.372

Repeatability and Agreement of Macular Thickness Measurement Using Time and Spectral Domain OCT in Diabetic Macular Edema

Se Beum Oh, MD, Jun Woong Moon, MD, Hyung Chan Kim, MD, PhD

Department of Ophthalmology, Konkuk University School of Medicine, Seoul, Korea

Address reprint requests to Hyung Chan Kim, MD, PhD Konkuk University Medical Center, Konkuk University School of Medicine #4-12 Hwayang-dong, Gwangjin-gu, Seoul 143-729, Korea Tel: 82-2-2030-5270, Fax: 82-2-2030-5273, E-mail: eyekim@kuh.ac.kr

Received 15 May 2009       Accepted 2 December 2009

Copyright © 2010 Korean Ophthalmological Society

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To evaluate the repeatability of macular thickness measurements using time domain (TD) OCT and spectral domain (SD) OCT in diabetic macular edema.

Methods

In 42 eyes of 42 patients with diabetic macular edema, three consecutive macular measurements were performed with TD OCT and SD OCT, and measurements for macular thickness and total macular volume obtained by the two OCTs were compared. The within-subject standard deviation (Sw), coefficient of variation (CVw), and intraclass correlation coefficient (ICC) were calculated to assess repeatability, with agreement between measurements assessed with Bland Altman plots. The correlations were also evaluated via the Pearson's correlation coefficient.

Results

The Sw of TD OCT and SD OCT for foveal thickness, total macular volume were 29.67 μ m/16.44 μ m, 1.26 mm3/0.23 mm3, respectively, and were significantly lower in SD OCT. The ranges of the respective CVw and ICC values were 1.10–2.78%, 0.78∼0.96 for TD OCT, and 0.29∼0.94%, 0.92∼0.99 for SD OCT. The SD OCT showed better repeatability for macular thickness measurements (all p≤0.001). The 95% limits of agreement for foveal and total macular volume were 88.9 μ m, 2.4 mm3, respectively. The Pearson's correlation coefficients of macular thickness and total macular volume between the two OCT methods were statistically significant (p=0.88–0.99).

Conclusions

Although both OCTs proved reliable for macular thickness measurements in diabetic macular edema, SD OCT shows better repeatability than TD OCT. Although macular thickness measurements obtained from the two OCTs cannot be used interchangeably, there were statistically significant correlations between measurements obtained using the two OCTs.

Keywords: Coefficient of variation, Intraclass correlation coefficient, Spectral domain OCT, Time domain OCT, Within-subject standard deviation

References

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Figure 1.
Bland-Altman plots of foveal thickness measurements obtained by Stratus OCT and Spectralis OCT. Solid line indicates the average mean difference, while dotted lines delineates the 95% confidence limits of agreement.
jkos-51-372f1.tif
Figure 2.
Bland-Altman plots of total macular thickness obtained by Stratus OCT and Spectralis OCT. Solid line indicates the average mean difference, while dotted lines delineates the 95% confidence limits of agreement.
jkos-51-372f2.tif
Table 1.
Baseline characteristics
Number of Eyes 42
Mean age ± SD* (years) 58.6 ± 8.2
Type of DME†  
Diffuse retinal thickness 16
CME‡ 23
Serous RD§ 3
Signal Strength  
Stratus OCT∏ 6.5 ± 0.5
Spectralis OCT (dB) 24.0 ± 3.7

* SD=standard deviation

† DME=diabetic macular edema

‡ CME=cystoid macular edema

§ RD=retinal detachment

∏ OCT= optic coherence tomography

Table 2.
Comparison of regional and total macular thicknesses measured by spectral domain and time domain optical coherence tomography
  Stratus OCT Spectralis OCT p-values Mean difference 95% limits of agreement
(mean± SD) (mean± SD) (SD OCT-TD OCT)
Foveal thickness 367.2±155.0 427.6±147.4 <0.001 60.4 88.9 (16.0–104.9)
Inner subfield thickness          
   Temporal 352.3± 96.1 413.7± 88.3 <0.001 61.4 113.5 (2.4–116.0)
   Superior 358.2± 89.4 419.8± 90.0 <0.001 61.6 100.1 (11.5–111.7)
   Nas al 358.1±102.8 425.1±100.6 <0.001 67.0 91.9 (16.0–107.9)
   Inferior 347.3± 94.2 404.8± 86.7 <0.001 57.4 120.7 (−2.9–117.8)
Outer subfield thickness          
   Temporal 274.4±+65.6 331.4± 67.0 <0.001 57.0 82.8 (15.6–98.4)
   Superior 286.2± 63.6 341.5± 63.7 <0.001 55.3 82.4 (14.1–96.5)
   Nas al 307.5± 70.6 361.3± 68.5 <0.001 53.7 92.0 (7.7–99.7)
   Inferior 274.9± 60.2 331.4± 54.5 <0.001 56.5 81.1 (6.0–87.1)
Total macular thickness 312.1± 96.6 367.0±100.0 <0.001 55.0 66.7 (21.6–88.3)
Total macular volume 8.6± 1.7 10.0± 1.6 <0.001 1.4 2.4 (0.2–2.6)
Table 3.
Within-subject standard deviation (Sw), coefficient of variation (CVw), and intraclass correlation coefficient (ICC) of total and regional macular thicknesses obtained with time domain OCT and spectral domain OCT
  Foveal Inner subfield thickness
 Outer subfiled thicknes
 Total Total
Thickness Temporal Superior Nasal Inferior Temporal Superior Nasal Inferior Thickness Volume
Sw TD OCT 29.67 T 23.71 31.84 20.94 34.73 13.81 17.31 14.27 31.38 8.56 1.26
SD OCT 16.44 T 24.54 16.15 14.93 13.10 8.88 8.97 12.54 9.50 5.08 0.23
CVw TD OCT 2.92 T 2.43 3.21 2.11 3.61 2.82 2.18 2.68 4.12 2.99 2.10
SD OCT 1.39 T 2.14 1.39 1.28 1.17 1.97 1.45 1.25 2.07 1.50 1.97
ICC TD OCT 0.921 T 0.934 0.937 0.932 0.924 0.917 0.893 0.784 0.843 0.912 0.801
SD OCT 0.952 T 0.963 0.962 0.956 0.942 0.931 0.919 0.903 0.924 0.897 0.932
p-value*   0.014 0.233 0.004 0.128 <0.001 0.005 0.001 0.018 <0.001 <0.001 0.002

* Companson of within-subject variances between stratus OCT and Spectralis OCT (paired t test on log-transformed data).

Table 4.
Within-subject standard deviation (Sw), coefficient of variation (CVw), and intraclass correlation coefficient (ICC) of total and regional macular thicknesses obtained with time domain OCT and spectral domain OCT between below 400 μm and over 400 μm
    FT< 400 μm (26 eyes)
   FT≥400 μm (16 eyes)
Fovea Total Total Fovea Total Total
Thickness Thickness Volume Thickness Thickness Volume
Sw TD OCT 21.64 8.31 0.26   44.03 10.52 0.32
SD OCT 14.25 3.77 0.16   27.15 7.42 0.45
        p=0. .012    
CVw TD OCT 2.48 2.03 1.85   3.07 3.04 2.38
SD OCT 1.19 1.38 1.60   1.72 2.65 2.48
        p=0. .043    
ICC TD OCT 0.930 0.922 0.825   0.909 0.899 0.782
SD OCT 0.961 0.925 0.941   0.937 0.882 0.920
p-value*   0.004 0.002 <0.001 0.269   0.052 0.015

* Companson of within-subject variances between stratus OCT and Spectralis OCT (paired t test on log-transformed data).

Table 5.
Pearson correlation coefficient of macular thicknesses and total macular volume obtained with time domain OCT and spectral domain OCT
  Foveal Inner subfielld thickness
 Outer subfiled thicknes Total Total
  Thickness Temporal Superior Nasal Inferior Temporal Superior Nasal Inferior Thickness Volume
Pearson                      
correlation coeffcient 0.98 0.94 0.97 0.97 0.94 0.91 0.97 0.93 0.88 0.99 0.95
p-value* <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

* Pearson's correlation coefficient between stratus OCT and spectralis OCT.

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