DIC (digital image correlation) combined with OCT (optical coherence tomography) serves as a crucial experimental approach for investigating retinal deformation during CME (cystoid macular edema). However, the measurement of retinal deformation in CME is often hindered by the difficulty in obtaining an accurate initial guess for DIC. By analyzing OCT image characteristics of CME, it is observed that regions distal to the fovea largely satisfy the rigid-body planar motion assumption. Based on this observation, a dual-seed-point-based method for DIC initial value estimation was proposed, along with three strategies for seed point selection. The proposed initial estimation method, integrated with DIC, was applied to measure the displacement fields of both healthy and retina affected by CME. Results indicate that the smallest initial estimation error is achieved when the intersection points of blood vessels on both sides of the fovea with the ellipsoid zone are selected as seed points. Furthermore, the method was applied to full-field deformation measurement in the retinal thickness direction of a CME patient, and the deformation evolution of the retina during CME was analyzed. The proposed initial value estimation method can assist DIC in achieving full-field retinal deformation measurement and analysis, providing an effective experimental tool for investigating the deformation mechanisms in CME.