Elsevier

Ophthalmology

Volume 115, Issue 8, August 2008, Pages 1366-1371.e1
Ophthalmology

Original article
Optical Coherence Tomography Measurements and Analysis Methods in Optical Coherence Tomography Studies of Diabetic Macular Edema

https://doi.org/10.1016/j.ophtha.2007.12.004Get rights and content

Objective

To evaluate optical coherence tomography (OCT) measurements and methods of analysis of OCT data in studies of diabetic macular edema (DME).

Design

Associations of pairs of OCT variables and results of 3 analysis methods using data from 2 studies of DME.

Participants

Two hundred sixty-three subjects from a study of modified Early Treatment of Diabetic Retinopathy Study (mETDRS) versus modified macular grid (MMG) photocoagulation for DME and 96 subjects from a study of diurnal variation of DME.

Methods

Correlations were calculated for pairs of OCT variables at baseline and for changes in the variables over time. Distribution of OCT measurement changes, predictive factors for OCT measurement changes, and treatment group outcomes were compared when 3 measures of change in macular thickness were analyzed: absolute change in retinal thickness, relative change in retinal thickness, and relative change in retinal thickening.

Main Outcome Measures

Concordance of results using different OCT variables and analysis methods.

Results

Center point thickness correlated highly with central subfield mean thickness (CSMT) at baseline (0.98–0.99). The distributions of changes in CSMT were approximately normally distributed for absolute change in retinal thickness and relative change in retinal thickness, but not for relative change in retinal thickening. Macular thinning in the mETDRS group was significantly greater than in the MMG group when absolute change in retinal thickness was used, but not when relative change in thickness and relative change in thickening were used. Relative change in macular thickening provides unstable data in eyes with mild degrees of baseline thickening, unlike the situation with absolute or relative change in retinal thickness.

Conclusions

Central subfield mean thickness is the preferred OCT measurement for the central macula because of its higher reproducibility and correlation with other measurements of the central macula. Total macular volume may be preferred when the central macula is less important. Absolute change in retinal thickness is the preferred analysis method in studies involving eyes with mild macular thickening. Relative change in thickening may be preferable when retinal thickening is more severe.

Section snippets

Materials and Methods

The specific objectives of this report are (1) to identify the optimal OCT measurement for central macular thickening in DME; (2) to identify roles for paracentral and global macular OCT measurements and explore correlations between these measurements and their changes in DME and treatments for DME; and (3) to identify limitations and advantages in 3 methods of analysis of OCT measurement changes—namely, (a) absolute change in thickness, (b) relative change in thickness, and (c) relative change

Optical Coherence Tomography Outcomes for the Center of the Macula

Center point thickness and central subfield mean thickness are 2 measures of the central portion of the macula printed on the Zeiss OCT Retinal Map Analysis. For the 2 studies, the correlation between these 2 measures at baseline was 0.98, and 0.99, respectively.2, 3 The correlation coefficients for change in CPT and change in CSMT in the mETDRS versus MMG trial and the diurnal variation study at their primary follow-up end points were 0.98 and 0.87, respectively.

As a result of these high

Preferred Optical Coherence Tomography Measurement for the Central Macula

Published studies on OCT measurements in DME have reported CPT and CSMT, often under synonymous names (Table 1 [available at http://aaojournal.org]). Chan and Duker were the first to identify the basis for preferring CSMT as a measurement of the central macular thickness, and we agree with their published rationale. They noted that CSMT should have a higher reproducibility because it is based on more scans than CPT. A DRCR.net reproducibility study in DME has confirmed this prediction.16 The

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    Manuscript no. 2007-1111.

    Supported through a cooperative agreement from the National Eye Institute, Bethesda, Maryland (nos. EY14231, EY14269, EY14229).

    A current list of the Diabetic Retinopathy Clinical Research Network and DRCR.net investigator financial disclosures are available at http://www.drcr.net.

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