Optimal optical coherence tomography-based measures in the diagnosis of clinically significant macular edema: retinal volume vs foveal thickness.

OBJECTIVE: To compare optical coherence tomography-based measures of retinal thickness and volume as quantitative tests for clinically significant macular edema (CSME). DESIGN: Diagnostic validation study. METHODS: Sixty-five eyes with diabetic retinopathy underwent stereo photographic and optical coherence tomographic examination. Stereo photographs were examined in a masked fashion to determine the presence or absence of CSME according to criteria from the Early Treatment Diabetic Retinopathy Study. Optical coherence tomography-based measurements of central foveal thickness as well as retinal volumes within a series of radii of fixation were generated. The main outcome measures were areas under receiver operating characteristic curves. Likelihood ratios, sensitivities, and specificities for the diagnosis of CSME were also evaluated. RESULTS: Retinal volumes within radii of 0.50 mm and 1.11 mm of fixation and central foveal thickness were the best variables for discriminating between those with and without CSME as evidenced by analysis of receiver operating characteristic curves. There were no significant differences among these 3 variables in their performance as diagnostic tests for CSME. CONCLUSIONS: Optical coherence tomography-based retinal volume and central foveal thickness variables display comparable abilities to discriminate between those with and without CSME. Both measures may have clinical applications as quantitative diagnostic tests for CSME.

Effect of eccentric and inconsistent fixation on retinal optical coherence tomography measures.

OBJECTIVE: To assess the relative stabilities of optical coherence tomography (OCT)-based retinal volume and central foveal thickness measurements in the setting of eccentric or inconsistent fixation. METHODS: Ten healthy right eyes underwent multiple macular OCT centered at fixation. To model the effect of eccentric or inconsistent fixation, OCT was repeated with scan centers precisely shifted by 0.50, 1.00, and 1.50 mm in each of 4 directions. At each scan location, retinal volumes within a series of radii of the scan center, as well as central foveal thickness, were calculated. The main outcome measure was the percentage effect of decentered scanning on each OCT-based variable. RESULTS: Central foveal thickness was the variable most affected in this model of eccentric and inconsistent fixation. This variable demonstrated changes from baseline-centered scans of up to 69.4%. Retinal volumes within a radii of the scan center measuring 1.11 mm or greater were least affected by decentered scanning, demonstrating maximum changes from baseline-centered scans of only 15.7% (P<.001 vs foveal thickness). CONCLUSION: Optical coherence tomography-based retinal volume quantification provides a more stable measure than foveal thickness in the setting of eccentric or inconsistent fixation as may occur in the setting of macular pathologic conditions.