Histopathology of the Ocular Surface

Three integral parts that cover the ocular surface are the conjunctiva, limbus, and cornea. The conjunctiva is a see-through mucous membrane that lines the internal surface of the eyelids and the front surface of the eyeball, ending at the limbus. It is highly vascular with a dense lymphatic network. The limbus forms the boundary between the transparent cornea and the opaque sclera. The cornea is a complex structure that provides a protective function and is responsible for about 75% of the optical power of the eye. Histology of these highly specialized biological materials as well as the ways in which individual components are structurally and functionally related will be discussed in this chapter. Then, we will go over the pathological oncology processes that can affect the ocular surface

Optic Nerve: Developmental Anomalies and Common Tumors

The optic nerve, also known as the second cranial nerve, is composed of axons that transmit visual information from the neurosensory retina to the visual cortex. There are multiple pathologies that can affect the human optic nerve. Congenital anomalies of the optic nerve include myelinated nerve fibers, morning glory syndrome, optic nerve choristoma, optic nerve coloboma, optic nerve hypoplasia and aplasia, and others. Tumors that can affect the optic nerve (ON) may occur primarily from within the nerve itself, from the surrounding optic nerve sheath (ONS), or secondarily spreading to the nerve from a distant site. They include optic pathway glioma, medulloepithelioma, oligodendroglioma, optic nerve sheath meningioma, and others. Here in this chapter, we will review the optic nerve anatomy, embryology, and physiology in addition to assessment of optic nerve function. Moreover, the clinical features, imaging findings, pathology, and treatment options of the most common and some rare congenital anomalies and primary tumors of the ON and sheath will be reviewed

Corneal Dystrophies and Degenerations

The cornea is a complex structure with complex functions aiming to protect the internal ocular tissues and transmit and refract the coming light rays. Corneal dystrophies are a group of relatively infrequent genetic corneal disorders in which an abnormal material accumulates in the cornea causing variable loss of its clarity. On the other hand, corneal degenerations are more common and usually result from physiologic changes related to aging, particular disease, or long-standing environmental insults to the cornea. Ectatic corneal disorders are usually characterized by bilateral loss of corneal biomechanical strength leading to progressive thinning and bulging of the cornea with resultant astigmatism and decreased visual acuity. In this chapter, we will describe the basic embryological, anatomical, histologic, and physiological features of the cornea. Then, we will go over the clinical, histopathologic, medical, and surgical aspects of dystrophic, degenerative, and ectatic corneal disorders

History and Genetics of Retinoblastoma

The history of retinoblastoma (RB) goes back to 1597 when Pieter Pawius of Amsterdam described a tumor that resembled retinoblastoma. “Fungus haematodes” was the first term used to describe retinoblastoma. Later, the American Ophthalmological Society approved the term retinoblastoma in 1926. The retinoblastoma protein is encoded by the RB1 gene located at 13q14. The functioning model of the tumor suppressor genes was first proposed by Alfred Knudson in the 1970s who precisely explained the hereditary mechanism of retinoblastoma. If both alleles of this gene are mutated, the protein is inactivated and this results in the development of retinoblastoma. One mutation can be either germline or somatic and the second one is always somatic. Differentiation between sporadic and germline retinoblastoma variants requires the identification of the RB1 germline status of the patient. This identification is important for assessing the risk of additional tumors in the same eye, the other eye, and the risk of secondary tumors. Thus, genetic testing is an important component of the management of all children diagnosed with retinoblastoma. In this chapter, we will go over the history, genetics, and counseling for patients with retinoblastoma