The pluripotential responses of retina, pigment epithelium, and choroid to a variety of pathogens produce a fascinating multiplicity of lesions which modify, often characteristically, the clinical picture of macular disease. The Retina I. Opacities of the Macular Retina. —Any foreign matter deposited within the retinal layers, as a result of either infiltrative, exudative, or proliferative processes, changes its index of refraction and becomes clinically visible as an opacity in the otherwise almost transparent structure. Unless caused by hemorrhage or pigment invasion the opacity is light in color. Three of the four types of whitish opacities occur frequently in the macular region. Lipoid Deposits: Clinically the individual lesion is small, discrete, and of brilliant pure white or yellowish-white color, depending upon the intensity of illumination. There is a tendency for grouping and confluence into arborescent or circinate patterns. They arise in areas of chronic relative anoxia, and in and around