Vitreous and Retina

Ferenc Kuhn

2.9.1 Introduction

In most cases the condition of the retina1 determines the outcome of an injury. In all cases of ocular (or systemic; see Chap. 3.3) trauma when posterior segment involvement can be suspected, vitreoretinal consultation should be sought. The earlier such consultation takes place the better. Many vitreoretinal surgeons also prefer if they are the one who sutures the cor-neal/scleral wound so that optimal conditions are established for vitrectomy, which may have be to performed in a very short period of time2 if this is deemed necessary to prevent secondary complications.

This chapter provides a summary of selected pathologies3 of the vitreous and retina,4 including management and certain prophylactic measures.5

1 More precisely, the viability the macula.

2 e.g., the corneal wound must remain watertight even if the IOP is raised during surgery, corneal edema must be minimized via the use of full-thickness sutures (see Chap. 2.2), and retinal incarceration into the scleral wound must be avoided.

3 Some of these conditions have a less obvious or direct relationship to trauma than others (e.g., vitreous opacities). Such conditions are discussed here because they may be a late, albeit rare, consequence of trauma.

4 The vitreous and retina are covered in a single chapter because many of their pathologies are interrelated.

5 Space limitations do not allow a complete description of all surgical techniques; for these the reader is referred to vitreoretinal textbooks.

2.9.2 Evaluation

If direct visualization of the vitreous and retina with the ophthalmoscope or at the slit lamp is not possible because of media opacity, several diagnostic tests are available that can provide important indirect information. These tests include determining the visual acuity (e.g., presence of LP and projection), ultrasonography, CT, MRI, UBM, and electrophysiology. Optical coherence tomography is an increasingly utilized test, although it requires clear media and its usefulness is mostly restricted for the chronic cases (Fig. 2.9.1). If concerns or doubts persist, surgical exploration (endoscopy or vitrectomy) must be considered (see Chap. 1.9).

2.9.3 Specific Conditions

2.9.3.1 Vitreous Penetration

Objects entering the vitreous cavity do not appear to cause adverse consequences if they are not contaminated, not retained, and do not cause concomitant damage6. In such cases the eye with vitreous penetration can simply be followed after wound closure7, and any intervention be deferred until a complication does occur. If the object was contaminated, is retained, or complications resulted, intraocular surgery is needed accordingly (see below and Chaps. 2.10, 2.13).

2.9.3.2 Vitreous Base Avulsion

Although the incidence after contusion reached 26% in one study [21], this is a rarely diagnosed condition. Even if neurofibromatosis [25] is one of the possible etiologies, vitreous base avulsion is pathognomonic of trauma8 [87].

6 e.g., significant vitreous hemorrhage or a retinal break

7 Wound closure is not always necessary (see Chaps. 2.2 and 2.3).

8 More precisely, contusion.

Fig. 2.9.1 Optical coherence tomography of an eye with traumatic macular pucker. The epiretinal membrane is clearly visible on the macular surface, causing full-thickness retinal folds

As a result of the blunt force applied to the eye, the vitreous base separates from the underlying retina and pars plana, which is recognized by a whitish line hanging from the periphery ("bucket handle sign"). No treatment is necessary unless secondary complications, such as retinal dialysis or tear, are also present. A careful retinal examination is therefore recommended.

2.9.3.3 Posterior Vitreous Detachment

This is perhaps the most commonly misinterpreted condition of all trauma-related posterior segment pathologies. By definition, this term should characterize a complete separation (Fig. 2.9.2a) of the postequatorial retina from the cortical vitreous, as opposed to a complete vitreous attachment (Fig. 2.9.2b). Posterior vitreous detachment (PVD) is often reported to occur in eyes with posttraumatic vitreous hemorrhage [16]. The vitreous may also be partially detached: there is strong vitreoretinal adhesion in an area surrounded by vitreoretinal detachment (Fig. 2.9.2c). Often, however, what is described after biomicroscopic, ultrasonographic, or OCT examination as a PVD is in reality a vitreoschisis (Fig. 2.9.2d). Such splitting of the vitreous can be present even if a Weiss ring is visible: separation of the vitreous from the retina at the optic disc does not necessarily imply that it has also detached at the macula [45].

Q Fig. 2.9.2 Vitreoretinal configuration and the risk of retinal detachment. a The vitreous is completely attached. Even if there are areas with abnormally strong vitreoretinal adhesion, there is no risk of retinal break and subsequent detachment development formation since the vitreous gel is stable: it is unable to shift position1 even with major and abrupt eye or head movement. b The vitreous is completely detached (true PVD). Although there is now room for the vitreous to shift with eye or head movement, it represents no risk for retinal break development lacking vitreoretinal adhesion.2 c Partial PVD, the only condition carrying a significant risk of retinal break formation. With eye or head movement, vitreous movement follows, exerting traction at the point of adhesion (arrow). In principle, there are two therapeutic approaches: to surround the area of adhesion with (laser) scars to overcome the traction force or to perform vitrectomy to eliminate the traction.3 d Vitreoschisis. Although the intra-vitreal presence of a hyaloidal face on examination suggests that a vitreous detachment has occurred, the vitreous in reality has split, and a layer is still adherent to the retina. There is fluid inside the vitreous pocket (syneresis)

1 i.e., cause dynamic traction.

2 Obviously, this is true only in the retinal area shown here: the risk may be substantial in other areas.

3 Presence of such an adhesion by itself is not an indication for vitrectomy, but if vitrectomy is performed for any other indication, the surgeon must make sure that the vitreous removal is complete and there is no residual traction.

O Cave

Based on current technology, it is impossible to preoperatively determine with absolute certainty that a true PVD has occurred. Even in-traoperatively, only intravitreally injected TA can provide indisputable evidence whether or not a layer of cortical vitreous still coats the retinal surface.

The vitreous is much less commonly detached after trauma than generally presumed. A recent study found that in eyes undergoing vitrectomy for a posterior segment IOFB a median 9 days (range 5-18 days) after the injury, only 19% of eyes had a PVD [88].

2.9.3.3.1 Management Pearls Regarding the Vitreoretinal Interface Posteriorly

Issues regarding management are as follows:

• Vitreous abnormalities, such as PVD, syneresis, and vitreoschisis, commonly occur with age or in certain conditions, e.g., myopia. Trauma can accelerate the development of these abnormalities, but true PVD within the first few weeks after an injury is much less common than suggested.

O Pearl

Since true PVD rarely develops in the first few weeks post-injury, this should not be a significant factor in determining the timing of vitrec-tomy (see Chap. 1.8). It is not recommended to delay vitreous surgery for the sake of PVD development, and it is best to assume during surgery that the vitreous is still attached.

• Posterior vitreous abnormalities do not require treatment unless they lead to secondary complications such as the development of an EMP or retinal tear.

• Very rarely, a posterior retinal break occurs as the vitreous with abnormally strong retinal adhesion detaches.9 Mobility of the vitreous (i.e., detachment in at least the adjacent area) is an obvious precondition.

• In eyes with complete vitreous attachment or detachment the risk of retinal break formation is virtually nonexistent (Fig. 2.9.2A,B).

• If the PVD progresses and involves the retina anterior to the equator, the risk of the development of a (peripheral) retinal break and subsequent detachment dramatically increases.

• A central retinal break, which is itself rarely a complication of PVD, virtually never causes retinal detachment. The only exception is an eye with high myopia.

9 The dynamic traction exerted by the vitreous overcomes the strength of retinal cohesion and adhesion.

• The risk of retinal detachment is even higher if the PVD is symptomatic. Recent complaints of flashes/floaters, however, do not necessarily indicate that a retinal break has occurred or even that it is imminent.

• If an area of abnormal vitreoretinal adhesion or a true retinal break is found in an eye with a history of trauma, prophylactic laser treatment is indicated. If prophylactic treatment is performed in the periphery, en-dolaser cerclage is more effective than focal laser [63] since the retinal detachment often originates in an area that appeared normal during the examination.

• If no treatment is employed, educating the patient about the symptoms of PVD and retinal detachment is just as important as performing periodic follow-up examinations using the slit lamp and a contact lens10.

2.9.3.3.2 Surgical PVD

The procedure should be part of every vitrectomy performed for trauma:

• If the retina and the vitreoretinal interface are visible and no significant traction is noted, the editor uses the postero-anterior technique [47], in which detachment of the posterior cortical vitreous takes precedence.

- Minimal vitrectomy is initially performed in front of the disc and macula.

- A tiny amount" of TA is injected to visualize the posterior vitreous.

- If the cortical vitreous is still adherent, it is either elevated using the vitrectomy probe at the disc margin and then in an increasingly larger circle, or it is incised and lifted with a slightly barbed MVR blade.i2

10 Traditionally, such examinations are advised at 3- or 6-month intervals. These intervals are arbitrarily chosen; there is no evidence why one interval would be preferable over any other.

11 Not exceeding 0.1 ml; if more is used, the clearing of the "intraocular snowfall" takes substantial time without contributing to the efficacy of the "staining."

12 To complete the vitrectomy, the entire vitreous is then removed while holding the vitrectomy probe in the midvitreous cavity. The last area to address is the periphery and the retrolental space.

• If there is significant vitreous opacity or vitreoretinal traction, the usual antero-posterior approach should not be used; the PVD follows the core vitrectomy. Areas of exceptionally strong vitreoretinal adhesion or of retinal necrosis require very careful decision-making and manipulations to avoid tearing and detaching the retina. If the risk is deemed high or the vitreous does not separate easily, it is safer to circumcise the vitreous (Fig. 2.9.3) with the vitrectomy probe, or, if the vitreous shows true sheets at the site, with scissors.

• One useful trick involves switching to air from BSS. The air will help keep the retina attached and the residual cortical vitreous somewhat compressed, providing decent visualization for the surgeon and allowing shaving of the inseparable vitreous.

A Controversial

Pharmacological vitreoretinal separation and vitreolysis, using enzymes13 [74, 81, 83], is a management option that holds promise for many conditions; it is probably most important in eyes with very strong vitreoretinal adhesion such as in young patients. Its efficacy in trauma remains to be determined.

2.9.3.4 Vitreous Opacities

Opacities may be present in the vitreous as a result several conditions such as inadequate absorption of a vitreous hemorrhage, infection, inflammation, or because of metallosis [73]. The only proven cure is vitrectomy; the patient's individual needs, rather than relying on an arbitrarily determined cut-off visual acuity level, should be the decisive factor in whether surgery is performed (see Chap. 1.4).M

13 e.g., plasmin, streptokinase, recombinant microplasmin, hyaloronidase, collagenase

14 Even if vision is 20/20, the floaters may cause major, unacceptable disturbance to some people. If the person understands and accepts the risks of surgery, this should not be denied by the ophthalmologist; if he feels strongly against the operation, the patient should be referred for second opinion.

Fore Skin Operation Level

Fig. 2.9.3 The "circumcision" option during vitrectomy in eyes with strong vitreoretinal adhesion or retinal necrosis. If the vitreous cannot be safely separated from the retina, it should be left in situ but truncated: severed from all connections from the rest of the vitreous, which must then be removed. Only a vitreous "plug" is thus left behind, but this represents no threat since it cannot exert traction on the retina. a Preoperative view. b Postoperative, cross-sectional view. c Postoperative, anterior view

2.9.3.5 Vitreous Hemorrhage15

This is the most common injury-related vitreous pathology (Table 2.9.1); one-third of eyes with serious trauma have vitreous hemorrhage (USEIR datum). The source of the blood may be any tissue from the iris anteriorly to the optic nerve head posteriorly.

2.9.3.5.1 Significance

• Vitreous hemorrhage interferes with the patient's visual acuity and field.

• It makes it difficult or impossible for the ophthalmologist to inspect the retina.

• It can cause secondary complications such as glaucoma,16 hemosiderosis [14], cataract, retinal gliosis and EMP, retinal detachment, PVR, myopia, and amblyopia [15, 30, 42, 50, 61, 78, 93].

• If the hemorrhage does not absorb spontaneously, it may be seeded with proliferative cells and undergo organization. The first sign of organization, a precursor to tractional retinal detachment and PVR, is decreased vitreous motility. Serial ultrasonography is often employed with the hope of detecting this complication early.

2.9.3.5.2 Treatment

Although there have been reports of successful nonsurgical treatment for trauma-related vitreous hemorrhage (recombinant activated factor VII [2], intravitreal hyaluronidase [52]), vitrectomy remains the mainstay of therapy. Vitrectomy achieves instantaneous clearing and allows instant treatment of any coexisting other intraocular pathology. The timing of vitrectomy remains a controversial issue; it is discussed in Chaps 2.10-2.14.

15 The blood may be located in the gel proper or in syneresis cavities; subhyaloidal bleeding is discussed separately.

16 Various types (see Chap. 2.18)

Table 2.9.1 The incidence of various vitreoretinal pathologies in different types of ocular trauma in the USEIR database (%)

Pathology

Contusion (1497)

Rupture (2117)

Penetrating (4220)

IOFB (1235)

Perforating (464)

Vitreous penetration

0 0

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