I. Anterior (see Chapter 18)

II. Posterior (congenital retinal septum; ablatio falciformis congenita)

A. Posterior persistent hyperplastic primary vitreous (PHPV; see Fig. 12.3) is most often unilateral and present at birth. Poor vision and strabismus are the most common presenting complaints.

B. Posterior PHPV consists of vitreous membranes extending from the disc usually toward the equatorial zone, posterior radial retinal fold (usually in the area of the vitreous membrane), disturbances of macular function, and neural retinal detachment.

I. Collapse and condensation of vitreous sheets with aging, especially in myopes, frequently cause the formation of strands and floaters.

II. Separation of the vitreous attachment to the optic disc after posterior vitreoretinal separation may cause a complete or incomplete ringlike floater (vitreous “peephole”; see subsection on vitreous detachment, later).

III. Symptomatic degenerative vitreous floaters may have a negative impact on the quality of life.

I. “Snowball” opacities (microabscesses) may occur with mycotic infections (especially with the mold fungi).

II. Whitish masses (“white balls”) may be seen inferiorly with vitreitis (e.g., sarcoidosis).

III. Numerous vitreous opacities, foamy “Whipple” macrophages, may be found in persons with Whipple’s disease (Fig. 12.4).

A. Whipple’s disease is a disorder of men, usually older than 35 years of age.

1. The detection of the causative agent, Tropheryma whippelii, by polymerase chain reaction allows confirmation of the clinical diagnosis.

2. The gram-positive bacteria, Arthrobacter species, phylogenetically related to T. whippelii, may also be causative agents.

B. Arthritis, fever, serous effusions, cough, lymphadenopathy, and malaise may occur for several years preceding the intestinal malabsorption, steatorrhea, and cachexia.

C. Ocular findings, in addition to vitreous opacities, include inflammations and ophthalmoplegia.

D. Foamy macrophages containing periodic acid–Schiff (PAS)-positive cytoplasm may be found in intestinal and rectal mucosa, mesenteric and extra-abdominal lymphatic tissue, heart, lungs, liver, adrenals, spleen, serous membranes, neural retina, and vitreous.

1. In addition, intracellular and extracellular rod-shaped bacillary bodies and serpiginous membranes are found by electron microscopic examination of macrophages.

2. It is now assumed that the characteristic macrophages derive their PAS-positivity from ingested rod-shaped bacilli (Tropheryma whippelii) and also from their residue in autophagic vacuoles of the macrophages.

I. Red blood cells in the vitreous compartment (see Figs. 12.11 and 12.12) are most often caused by neural retinal tears but may have other causes. Red blood cells may be subvitreal (between vitreous body and internal limiting membrane of the neural retina) or intravitreal (within the vitreous body).

II. Hypoxia of the vitreous body may be demonstrated when blood enters it in a patient who has sickle-cell trait or disease.

A. Sickling and hemolysis of the erythrocytes increase toward the central vitreous, the most hypoxic area.

B. On histologic examination of a vitreous specimen or an enucleated globe, occasionally the diagnosis of sickle-cell trait or disease is made in a person not known previously to be so affected.

I. Asteroid hyalosis (Benson’s disease; Figs. 12.5 and 12.6) consists of complex lipids embedded in an amorphous matrix containing mainly calcium and phosphorus and attached to the vitreous framework.

A. Diabetes mellitus is a major risk factor; other risk factors include systemic hypertension, atherosclerotic vascular disease, and hyperopia.

B. Asteroid hyalosis has the following clinical properties:

1. Asteroid bodies remain attached to collagenous framework and move only when the framework oscillates. They are seen as gold balls when viewed with side illumination (e.g., with the ophthalmoscope) and appear white with direct illumination (e.g., with the slit lamp).

2. The condition is usually unilateral and most common in the seventh and eighth decades of life. It is infrequently associated with neural retinal detachment.

C. Histologically, asteroid bodies consist of an amorphous matrix that is both PAS-positive and acid mucopolysaccharide-positive and contains birefringent, small crystals when viewed with polarized light. Electron microscopically, the bodies are composed of finely laminated ribbons of complex lipids, especially phospholipids, lying in a homogeneous background and intertwined with filaments of vitreous framework.