29.1.1 Clinical Features

PVD may be asymptomatic or may be associated with variable symptoms, typically new-onset floaters and/or photopsias. Characteristically, floaters move with eye movements and continue to show motion after eye movements have stopped. Patients sometimes have difficulty separating a truly floating dark spot from a central scotoma, which also moves with eye movements but remains in exactly the same position relative to the center of gaze.

Photopsias, or light flashes, may be caused by stimulation of the retina from a partial or complete detachment of the formed vitreous from the retina and are usually perceived as crescents of light in the peripheral visual field. Photopsias are most visible in the dark or in dim light conditions. In some cases, if vitreous hemorrhage accompanies the PVD, the presenting symptom may be blurred vision, which may vary in severity.

29.1.2 Diagnosis

Although a PVD is generally a benign occurrence, it must be differentiated from pathologic conditions that may present with similar symptoms and findings.

Examination of the vitreous after an uncomplicated PVD may yield only subtle clues to its occurrence. The most convincing evidence of PVD is the finding of a complete or partial ring of tissue suspended in the vitreous cavity (Vogt or Weiss ring; Fig. 29-1), representing the fibrous remnants of the relatively tight attachment of the vitreous to the optic disc. ⁴ An optically empty zone posterior to biomicroscopically visible formed vitreous is frequently taken as evidence of PVD, although this often represents a pocket of liquified vitreous with a layer of cortical vitreous still adherent to the retina. The truly separated posterior hyaloid has a characteristic appearance, like that of wrinkled cellophane, anterior to an optically empty region.

The presence of anterior or posterior vitreous pigment clumps (also called “tobacco dust” or “Shafer’s sign”) in an eye that has not undergone surgery or other trauma is suggestive of a retinal tear. Vitreous white blood cells may indicate an inflammatory condition such as multifocal choroiditis/panuveitis, which often presents with both floaters and photopsias. Any inflammatory condition capable of producing vitreous inflammatory cells, or the presence of malignant cells in the case of intraocular lymphoma, can produce floaters.

The finding of blood in the vitreous cavity should prompt a search for sources of bleeding, particularly a retinal tear. An acute PVD with vitreous hemorrhage has an up to 70% incidence of retinal tears, compared with a 2 to 4% incidence in acute PVD without hemorrhage. Other sources of blood, with or without PVD, include retinal or optic disc neovascularization secondary to such etiologies as branch retinal vein occlusion or proliferative diabetic retinopathy, and choroidal neovascularization with breakthrough bleeding.

29.1.3 Pathogenesis

The vitreous is an important structure during embryologic development, and undergoes three distinct stages of development. ⁵ Initially, the primary vitreous supplies vasculature to the developing eye. The primary vitreous reaches its most vascular stage near the ninth week of gestation, after which the vessels normally atrophy. The primary vitreous is then replaced by an avascular, clear secondary vitreous, leaving the primary vitreous occupying a central tubular structure extending from the optic disc to the posterior surface of the lens, Cloquet’s canal. At the time of birth, the blood vessels have normally disappeared, although remnants of Cloquet’s canal may persist near the posterior pole of the lens (Mittendorf dot) or on the optic disc (Bergmeister’s papilla). Rarely, the primary vitreous fails to involute, and the resulting condition, persistent fetal vasculature (formerly called “persistent hyperplastic primary vitreous”), is associated with cataract, vitreous opacities, and a poor prognosis for vision.

Vitreous is comprised of 99% water. Contained in the water are collagen fibrils, cross-linking the entire volume of formed vitreous, and dissolved hyaluronic acid, forming a clear gel. ⁶ In the adult, the normally clear vitreous serves no apparent essential function, and changes in the vitreous can be responsible for a number of abnormal conditions.

In the normal young eye, the vitreous fills virtually the complete posterior cavity of the eye and is in contact with the entire retina. It is anchored most securely at the vitreous base, a zone of 3 to 4 mm that extends from the pars plana posteriorly across the ora serrata and into the anterior retina. Weaker zones of vitreous attachment include the optic disc, retinal vessels, and sites of abnormal vitreoretinal conditions, such as at the margins of lattice degeneration.

As a consequence of aging, the vitreous fibrils condense and shrink. Initially, large clear spaces or lacunae, which may be difficult to differentiate from vitreous detachment, may be visible at the slit lamp. With continued shrinkage of the vitreous body, the vitreous usually separates from the retina beginning at the macula. Once vitreous detachment has begun, it typically proceeds rapidly to a funnel-shaped configuration, with attachment anteriorly in a large annulus at the vitreous base; posteriorly, a small annulus is attached to the optic disc. Finally, the attachment at the disc releases and the posterior hyaloid becomes free-floating. Once the posterior hyaloid face has completely separated from the retina up to the vitreous base, no further spontaneous separation can occur (Fig. 29-2).

29.1.4 Management and Course

The most important consideration in the management of a patient with PVD is to search for retinal tears. Once the symptoms of floaters and/or photopsias have begun, the patient should be examined at intervals until the separation has completed. A reexamination in 4 to 6 weeks after the symptoms have begun is generally appropriate, along with the admonition to return sooner if symptoms increase or change substantially.

29.2.1 Clinical Features

The term retinal tear is usually used to describe a full-thickness defect or break in the retina caused by traction exerted from the vitreous. A tear, as opposed to a round hole, contains a flap that gives the characteristic appearance of a horseshoe (Fig. 29-3). In contrast, atrophic retinal holes are full-thickness retinal defects in which vitreous traction is not the primary pathogenetic mechanism. The term hole should not be used interchangeably with tear because their appearance, pathogenesis, and risk for associated retinal detachment are different (Fig. 29-4).

Occasionally, the flap of a retinal tear will separate and create a free-floating operculum. In an operculated tear, vitreous traction on the retina is released. The resulting retinal defect is usually round, and the avulsed flap of retina (the operculum) can be seen floating in the vitreous cavity in the vicinity of the tear (Fig. 29-5).

Lattice retinal degeneration may be associated with atrophic holes, retinal tears, or both. ¹¹ Lattice is found in about 5 to 10% of the population and is bilateral in one-third of affected individuals. It can have a variable ophthalmoscopic appearance. Often, there is increased pigmentation in lattice lesions, and the overlying blood vessels may appear white, giving the appearance of latticework (Fig. 29-6). Another variant of lattice is termed “snail track” degeneration, in which the appearance is white rather than hyperpigmented. ¹² There may be a pocket of fluid in the overlying cortical vitreous and retinal thinning (Fig. 29-7). Increased vitreoretinal adhesion at the edge of lattice may give rise to retinal tears at the posterior margin.

Lattice retinal degeneration typically occurs in curvilinear patches between the equator and ora serrata, near the posterior margin of the vitreous base. These patches are usually oriented circumferentially in one or more rows, although lattice may occur radially along retinal blood vessels. Atypical presentations of lattice degeneration may be seen in hereditary vitreoretinal degenerations (e.g., Wagner’s syndrome, Stickler’s syndrome) in which multiple patches of lattice, some of which are radial, occur in conjunction with a liquified or optically empty vitreous cavity. Retinal tears may occur at the margins of lattice degeneration. Byer ¹¹ noted, however, that in eyes with lattice degeneration, many retinal tears that occur do so in previously normal-appearing retina.

In contrast to lattice degeneration, cobblestone or pavingstone degeneration is a peripheral fundus finding that is not associated with retinal breaks and that should not be confused with lattice degeneration. Areas of cobblestone are sharply demarcated zones through which bare sclera or large choroidal vessels may be seen (Fig. 29-8).

Retinal tears may range in size from only a fraction of a millimeter up to several clock hours. A giant retinal tear, by definition, extends 3 or more clock hours (=90 degrees). ¹³ The vitreous is adherent to the anterior retina in a giant retinal tear, just as it is in a horseshoe tear. The posterior edge of retina has no adherent vitreous, which allows it to detach and scroll up, exposing a large area of bare retinal pigment epithelium (RPE) (Fig. 29-9). On casual viewing, the exposed RPE may have the appearance of a normal fundus, but closer scrutiny reveals the absence of retinal vessels.

A type of retinal break that may be confused with a giant retinal tear is a retinal dialysis. Unlike other retinal tears, which typically occur at the posterior margin of the vitreous base, a retinal dialysis (from the Greek for “separation”) occurs at the ora serrata. Therefore, in a dialysis, the vitreous spans the break and is adherent to both the anterior and the posterior retinal edges (Fig. 29-10). This very important difference from a giant tear prevents the posterior edge of the retina from folding over, and helps to give the dialysis a far better surgical prognosis. ¹⁴ As with the giant retinal tear, a dialysis can extend circumferentially over several clock hours. The most common location for a dialysis is in the inferotemporal quadrant, but it may also occur in the superonasal quadrant following blunt trauma.

29.2.2 Diagnosis

The detection of retinal breaks may be an arduous task, the success of which depends greatly on the skill and experience of the examiner, using slit-lamp biomicroscopy with hand-held condensing lenses, indirect ophthalmoscopy, or both. Scleral depression may be very helpful for viewing the retina in profile. Because retinal flap tears are three-dimensional, viewing the retina in profile with scleral depression may allow detection of breaks that are not visible when viewed frontally.