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.