Image Quality Affects Macular and Retinal Nerve Fiber Layer Thickness Measurements on Fourier-Domain Optical Coherence Tomography

BACKGROUND AND OBJECTIVE: To investigate whether image quality is an important determinant of retinal nerve fiber layer (RNFL) and macular thickness measurements on Fourier-domain optical coherence tomography (OCT). PATIENTS AND METHODS: Seventy-five and 56 normal subjects were recruited in RNFL and macular thickness arms of the study, respectively. Each participant was scanned three times using both the 3D OCT-1000 (version 3.01, Mark II; Topcon Corporation, Tokyo, Japan) and the Cirrus OCT (version 3.0, Model 4000; Carl Zeiss Meditec, Inc., Dublin, CA). The scans for each participant were arranged in order of increasing image qualities, which were correlated with RNFL and macular thicknesses. Subgroup analyses were performed with identical versus different and high versus low image quality metrics. RESULTS: Higher image quality was significantly correlated with greater RNFL thickness measurements on the 3D OCT-1000, and when the signal strength was less than 7 on the Cirrus device. Image quality metrics were negatively correlated with measured macular thicknesses on Cirrus OCT but not on 3D OCT-1000. CONCLUSION: Image quality metrics should be considered when evaluating thickness measurements derived from Fourier-domain OCT devices.