This chapter provides detail description of elementary OCT lesions. This chapter has 48 well illustrated diagrams, pictures and images. Elementary lesions index, retinal outline elementary lesions, retina and choroid cavities, cystoids edema, juvenile X linked macular retinoschisis, vascular cavities, arterial macroaneurysm, outer retina tabulation, nicotinic acid maculopathy, peripapillary choroidal cavities, dense formation and deposits, exudates, subretinal deposits, neovascular membranes, variations in thickness of retinal layer, atrophy-dystrophy of retinal layers, pigment epithelium alterations, choroid lesion and decreased choroidal thickness are given in detail. 10 flow charts are given to highlight lesions, holes and cavities in retina. 57 tables are given to depict salient features of different retina diseases and conditions seen on OCT.