The vitreous humor makes up most of the volume of the globe and is important in many diseases that affect the eye (Fig 10-1). The vitreous body is divided into 2 main topographic areas: the central, or core, vitreous; and the peripheral, or cortical, vitreous. See BCSC Section 2, Fundamentals and Principles of Ophthalmology, and Section 12, Retina and Vitreous, for discussion of the anatomy of the vitreous. The strength of vitreoretinal adhesion or attachment is important in the pathogenesis of retinal tears and detachment, macular hole formation, and vitreous hemorrhage from neovascularization.
The embryologic development of the vitreous is generally divided into 3 stages: primary, secondary, and tertiary (see Figure 4-11 in BCSC Section 2, Fundamentals and Principles of Ophthalmology). The primary vitreous consists of fibrillar material, mesenchymal cells, and vascular components (hyaloid artery, vasa hyaloidea propria, and tunica vasculosa lentis [see Fig 4-3 in BCSC Section 11, Lens and Cataract]). The secondary vitreous begins to form at approximately the ninth week of gestation and is destined to become the main portion of the vitreous in the postnatal and adult eye. The primary vitreous atrophies with formation of the secondary vitreous, leaving only a clear central zone through the vitreous (called the hyaloid canal, or Cloquet canal) and its anterior extension, the hyaloideocapsular ligament (also known as ligament of Weiger) (see Fig 10-1). The secondary vitreous is relatively acellular and completely avascular. It is composed of thin collagen fibrils and hyaluronic acid (hyaluronan), which is extremely hydrophilic. Although the vitreous cavity typically appears empty on routine histologic sections, the hyaluronic acid will stain with alcian blue. The rare cells present in the secondary vitreous are called hyalocytes. The lens zonular fibers (also referred to as the zonule of Zinn) represent the tertiary vitreous.
Figure 10-1 Schematic of the topography of the vitreous body demonstrating distribution of the collagen fibrils (lines) at the vitreous base, at the cortex, in the macular region, and at the optic nerve head.
(Illustration by Cyndie C. H. Wooley.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.