Three-dimensional Imaging of Cystoid Macular Edema in Retinal Vein Occlusion

Abstract

To study the pathomorphologic features of cystoid macular edema (CME) associated with retinal vein occlusion by three-dimensional (3D) optical coherence tomography (OCT) and to study the relationship of the ocular findings to visual function. Observational case series. Twenty eyes of 20 patients with retinal vein occlusion. A prototype 3D OCT system based on Fourier-domain OCT technology was fabricated for patient examination in this study. This system uses a superluminescent diode, which has a center wavelength of 830 nm and a bandwidth of 50 nm, as the light source, resulting in 4.3-microm axial resolution in tissue. Data acquisition rates of approximately 18 700 axial scans per second and a sensitivity of 98 dB were achieved. Three-dimensional imaging was performed by volume rendering based on the 3D data set acquired with a raster scan of 256x256 axial scans. Images of CME pathologic features obtained by 3D OCT and by Stratus OCT (Carl Zeiss, Dublin, CA). The 3D OCT imaging system generates a realistic 3D image of CME with high resolution. In 16 eyes, 3D OCT showed large foveal cystoid spaces, most of which were accompanied by small cystoid spaces in the parafoveal region. Cystoid spaces were seen often in the inner nuclear layer and outer plexiform layer, but were detected to some extent in all retinal layers. The 3D OCT showed clearly a thin back-reflecting line corresponding to the external limiting membrane (ELM) in 18 eyes; of these, cystoid spaces were located on the inside of the ELM in 7 eyes and appeared to be in contact with the ELM in 9 eyes. In 2 eyes, the ELM line could not be seen clearly beneath the large foveal cystoid spaces. Integrity of the ELM in the foveal region had a direct correlation with visual acuity. Observation of CME using 3D OCT enabled visualization of its spatial extent in each retinal layer and discernment of its relationship to the ELM. The use of 3D OCT thus may improve the monitoring of CME progression and its response to treatment.