Section 4 presents materials in two parts: Part I, Ophthalmic Pathology; and Part II, Intraocular Tumors. Part I uses a hierarchy that moves from general to specific to help derive a differential diagnosis for a specific tissue. Part II is a compilation of selected clinical aspects of importance to the general ophthalmologist. Additionally, this section has a variety of images and videos. Upon completion of Section 4, readers should be able to: Describe a structured approach to understanding major ocular conditions based on a hierarchical framework of topography, disease process, general diagnosis and differential diagnosis. Summarize the steps in handling ocular specimens for pathologic study, including obtaining, dissecting, processing, and staining tissues. Identify those ophthalmic lesions that indicate systemic disease and are potentially life threatening.