Relationship between fluorescein pooling and optical coherence tomographic reflectivity of cystoid spaces in diabetic macular edema

Objective: To study the characteristics of the reflectivity of the cystoid spaces and serous retinal detachment (SRD) on spectral-domain optical coherence tomography (SD-OCT) and the correlation with fluorescein findings in diabetic macular edema (DME).

Design: Retrospective, observational, cross-sectional study.

Participants: Consecutive 134 eyes of 114 patients with clinically significant macular edema for whom SD-OCT and fluorescein angiography (FA) were performed on the same day.

Methods: Fluorescein angiography using Heidelberg Retina Angiograph 2 (Heidelberg Engineering, Heidelberg, Germany) and OCT images using Spectralis OCT (Heidelberg Engineering) were obtained. The reflectivity of the cystoid spaces and SRD on the OCT images was evaluated qualitatively and quantitatively and compared with the fluorescein pooling intensity on FA images.

Main outcome measures: The relationship between the fluorescein pooling and the reflectivity characteristics of the cystoid spaces on SD-OCT images.

Results: A total of 141 cystoid spaces in 101 eyes were delineated on OCT images, and 138 spaces (97.9%) had fluorescein pooling. Fifty-five cystoid spaces (39.9%) with marked fluorescein pooling intensity had lower reflectivity on OCT images than those with modest pooling (12.1±10.4 vs. 22.0±15.4, P < 0.001). The heterogeneity of the reflectivity of the cystoid spaces on the OCT images was associated significantly (P < 0.001) with modest fluorescein pooling. The hyperreflective foci in the cystoid spaces were correlated significantly with modest fluorescein pooling and higher or heterogeneous reflectivity on OCT images (P < 0.001, P < 0.001, and P=0.005, respectively). In addition, the cystoid spaces with microaneurysms had higher or heterogeneous reflectivity on OCT images more frequently than those without microaneurysms (P < 0.001 and P=0.019, respectively). The reflectivity levels in the SRD were significantly (P=0.005) lower than in the cystoid spaces, and only 1 eye (3.3%) had heterogeneous reflectivity on OCT images.

Conclusions: The results provided a novel interpretation of fluorescein pooling and OCT characteristics of cystoid spaces and SRD in DME and suggested several mechanisms by which the blood-retinal barrier is disrupted and concomitant edematous changes develop.