Optical coherence tomography (OCT). A, OCT scan showing normal foveal depression and retinal thickness. Note that the RPE/Bruch membrane appears red and the vitreous appears dark. B, Scan of a patient with diabetic macular edema and vitreous traction. Note the posterior hyaloid (yellow arrow) pulling on the retina, a fine epiretinal membrane (white arrow) on the retinal surface, and the increased retinal thickness.