Purpose: The reflectivity of optical coherence tomographic (OCT) images has been used to evaluate retinal diseases. The purpose of our study was to determine whether a significant correlation exists between the reflectivity of the subretinal fluid (SRF) and the concentration of intravitreal cytokines in eyes with diabetic macular edema (DME).
Methods: A retrospective comparative study was done of eyes with DME with SRF before vitrectomy. The reflectivity of the SRF was determined from the OCT images. Vitreous samples were collected during vitrectomy, and analyzed for the concentrations of VEGF, IL-6, and IL-8. To determine the factors in the SRF that could affect the reflectivity, the aqueous humor of isolated swine eyes was replaced by saline with plasma, albumin, or fibrinogen, and the reflectivity of the anterior chamber was determined by anterior segment OCT.
Results: The average OCT reflectivity of the SRF was 3.52 arbitrary units (AU; 15 eyes; range, 0.01-20.7 AU). The average concentration of VEGF was 870.1 pg/mL, that of IL-6 was 131.7 pg/mL, and that of IL-8 was 224.1 pg/mL. The degree of OCT reflectivity was correlated significantly with the intravitreal VEGF concentration (r = 0.516, P = 0.049, Spearman's rank correlation coefficient), but not with IL-6 or IL-8. In the swine eyes, the presence of plasma, bilirubin, and fibrinogen in the anterior chamber led to significant increases in the reflectivity.
Conclusions: The significant correlation between the reflectivity of SRF and intravitreal VEGF indicates that OCT can be used to monitor the level of VEGF in eyes with DME.
Keywords: OCT; VEGF; diabetic retinopathy; reflectivity.