The purpose of this text is to depict and analyze the photoreceptor integrity line (PIL) or the IS/OS junction of the inner and outer segments in the normal and abnormal eyes with macula and retinal diseases. This book includes 67 cases that fall into the following categories; congenital, acquired, retinal vascular disorders, hereditary chorioretinal dystrophies, myopic degeneration and age related macular degeneration. In each case presented, the PIL/junction serves as a biomarker that represents the integrity of both rods and cones.