DME is defined as retinal thickening within 2 disc diameters of the center of the macula. Focal edema is associated with hard exudate rings resulting from leakage from microaneurysms. Diffuse edema results from breakdown of blood-retinal barrier with leakage from microaneurysms, retinal capillaries, and arterioles. Poor control of blood sugar increases the risk of diabetic retinopathy. Renal disease can be a marker for the development of diabetic retinopathy.
Systemic hypertension increases the risk of diabetic retinopathy.
Elevated lipid levels increase the risk of leakage and exudate deposits. It distinguishes and localizes areas of focal versus diffuse leakage, thereby guiding the placement of laser photocoagulation. The proximity of the leakage to the foveal avascular zone should be noted. Color stereo fundus photographs provide an opportunity to evaluate long-term changes in the retina. Optical coherence tomography Optical coherence tomography captures reflected light from retinal structures to create a cross-sectional image of the retina, which is comparable to histologic sections as seen with a light microscope.