Vitreous surgery techniques have greatly improved the management of ocular trauma. Work-related activity, home maintenance, automobile and motorcycle accidents, fireworks, hunting, violence, and recreational activity create a continued threat of severe ocular injury. The vast range of objects and velocities implicated in ocular trauma lead to the wide spectrum of injuries seen (1). In this chapter, the emphasis will be placed on several stereotypic subgroups.

WOUND-RELATED CELLULAR MIGRATION/PROLIFERATION

Any interruption of tissue results in proliferation of the interrupted cell groups. Planar cell groups respond to loss of contact inhibition by a migration/proliferation of the cells adjacent to the interruption. Misalignment of the proliferating plane may result in reduplication of the original tissue layer. Migration/proliferation ceases when contact inhibition is restored by continuity of the new cell group with similar cells representing the margin of defect. This new structure can be called a membrane; however, it is actually a reparative extension of previously normal tissues. The widely used term “fibrovascular ingrowth” implies that wound-related cellular proliferation originates from extraocular tissues. The severe proliferation that occurs in blunt trauma after choroidal rupture (retinitis sclopetaria) is clinically indistinguishable from “fibrovascular ingrowth.” There is little direct evidence of extraocular origin for the majority of cases of wound-related cellular proliferation. Because the reparative mechanism stems from tissue disruption and destruction, the additional damage of retinopexy should be avoided unless necessary for the treatment of a retinal defect. Silicone oil can be used for what the authors term “retinopexy avoidance” in the setting of severe trauma with retinal breaks.

SUBSTRATES FOR PROLIFERATION

Cellular proliferation occurs on preexisting support substrates such as the cornea, retina, vitreous, lens, and iris. The vitreous has been referred to as a “scaffold” (2,3), but this is a substrate. Substrate better describes the manner in which cellular migration and proliferation occur on the vitreous collagen matrix. More accurately, it is critical to recognize that proliferation usually occurs along the anterior vitreous cortex (AVC) and posterior vitreous cortex (PVC), although a foreign object can make a path through the vitreous along which apparent transvitreal proliferation can occur. As the retina is an ideal substrate for proliferation, it is not necessary to implicate the vitreous when epiretinal cellular migration and proliferation occur.

TIMING OF VITRECTOMY

Immediate vitrectomy in penetrating ocular trauma cases should be avoided unless certain types of intraocular foreign bodies (IOFBs) are present. The experience of the Iraq war has shown that primary closure of entry wounds with delayed removal of the IOFB can have good outcomes (4). Arterial bleeding, choroidal swelling, leaking wounds, striate keratopathy, corneal edema, and lack of preparation add to the difficulty of immediate vitrectomy (5,6). More importantly, penetrating trauma frequently occurs in the young patient not having a posterior vitreous detachment (PVD). Without adequate vitreoretinal separation, iatrogenic retinal breaks, difficult surgery, and postoperative contraction of residual vitreous can ensue.

Typically, the hemorrhage and inflammation that accompany trauma induce a PVD in 7 to 14 days, allowing safer, more effective vitreous surgery. Cellular proliferation starts at 10 to 14 days, making this the ideal time to intervene (7,8). If the retina can be seen, these cases can be watched at weekly intervals and vitrectomy avoided if cellular proliferation does not occur. Cases with opaque media require vitrectomy at this 10- to 14-day point because further delay could lead to cellular proliferation, which is initially difficult to determine with B-scan ultrasound. Decreased vitreous mobility observed on ultrasound examination indicates hypocellular vitreous collagen contraction and/or early cellular proliferation.

INTRAOCULAR FOREIGN BODIES

Vitreous surgery allows excellent visualization; prevention of postoperative transvitreal proliferation; and removal of blood, lens materials, and organisms if present. Bronson or giant magnet foreign body removal has virtually disappeared because of the widespread availability of vitreous surgery training, technology, techniques, and the Machemer-Parel diamond-coated IOFB forceps (Fig. 23.1). Intraocular magnets can be used to pick up foreign bodies for transfer to diamond-coated forceps and removal, although this is seldom necessary (9–15).

Figure 23.1 Diamond-coated foreign body forceps prevent dropping and grasp-induced movement of the IOFB.

Inert Versus Toxic Foreign Bodies

Most iron- and copper-containing foreign bodies should be removed immediately (16,17). Stainless steel, aluminum, and lead foreign bodies are much less toxic and can be tolerated in selected cases. Indication for removal of these less toxic materials must be individualized on a clinical basis. Occasionally, iron- and copper-containing foreign bodies will be overlooked and only discovered after they have become encapsulated. If no evidence of toxicity is seen in these cases, frequent follow-up should be undertaken rather than surgery. Clinical examination of adjacent structures (cornea, iris, and lens) is probably a better indication of toxicity than electroretinography. Plastic materials can be left in place in selected cases. Submacular foreign bodies and those embedded in the optic nerve should be managed on an individual basis because of the extreme hazards of removal. Any exogenous biologic material such as vegetable matter should be removed immediately because of the risk of infection and inflammation. Endogenous cilia and bone fragments are usually well tolerated and need not be removed unless vitrectomy is performed for other reasons or they appear to be the cause of inflammation.

Timing of Surgery

All large, toxic, biologic, or sharp IOFBs should be removed as soon as the patient can be safely taken to the operating room. This approach decreases secondary mechanical trauma, rapid toxicity, and endophthalmitis. Plastic, glass, and lead shotgun pellets can be observed until vitrectomy is indicated for other reasons. Although late-night and weekend vitreous surgery creates logistical and cost problems, it decreases the risk of endophthalmitis and toxic damage and should be undertaken if possible.

Surgical Sequence and Techniques

Wound Repair

Any visible corneal or scleral wound should be sutured before proceeding with the vitrectomy. Running shoelace monofilament nylon sutures distribute stress evenly, are elastic and well tolerated, and may be rapidly placed. Silk sutures are inelastic and lead to wound leaks during the vitrectomy, while absorbable sutures are inelastic and not permanent. Interrupted sutures can cause striate keratopathy and take longer to place. Small sutures (10-0) are used for central cornea, 9-0 for midcornea, and 8-0 for peripheral cornea or sclera.

Surgical judgment should guide the decision-making process concerning excision of prolapsed tissue. Viable-appearing iris or ciliary body in a very recent injury can be irrigated and repositioned, while any sign of infection or tissue destruction indicates excision. Retinopexy should not be used anterior to the muscle ring (ora serrata) and should be applied only to definite retinal breaks located posteriorly. Excessive and unnecessary retinopexy leads to greater wound-related cellular proliferation and inflammation. Endolaser retinopexy should be applied only to specific breaks identified during vitrectomy.

Exploration of/for a posterior wound should be done only if pressure on the globe can be completely avoided. The vitreous and retina can be prolapsed from a posterior wound by surgical manipulation. If vitrectomy is completed first, the location of the wound will be known, and the eye can be softened and filled with air (gas) before proceeding with posterior wound repair in the rare instance that it is thought to be necessary. Most posterior wounds are self-sealing, and wound closure does not decrease the incidence of wound-related cellular proliferation. Retinopexy increases the incidence of wound-related cellular proliferation and should be avoided.

Conjunctival Incisions

The authors currently use 25-gauge sutureless vitrectomy for all trauma cases and open the conjunctiva selectively only to repair scleral wounds and to construct a one clock-hour incision when a superotemporal 25-gauge wound is enlarged to 20 gauge or larger for IOFB removal.

Sclerotomies

The incision for the vitrectomy instrument, infusion cannula, and endoilluminator should be made in the usual position, 3 mm posterior to the limbus if the lens is to be removed or 4 mm posterior to the limbus if not. Extra care must be taken to avoid choroidal infusion in trauma cases because hypotony and choroidal edema are frequently present.

The incision for the foreign body removal should usually be the superotemporal vitrectomy instrument incision, enlarged after the vitreous is removed using a diamond or disposable knife.

Lens Removal

If the lens is clear, it should be allowed to remain unless a very large foreign body requires translimbal removal. Many small, localized traumatic cataracts do not progress and therefore may not require removal. The vitrectomy instrument should be used for anterior vitrectomy if any vitreous is in the anterior chamber or capsular bag. The aspirating fragmenter is faster than vitrectomy instruments for lensectomy but should never be applied to the vitreous. If vitreous enters the capsular bag, it should be removed with a vitrectomy instrument and the lensectomy completed with the fragmenter. In most cases, the capsule should be removed with the diamond-coated or end-grasping forceps.

Vitrectomy

The vitreous may be clear or have significant hemorrhage in acute IOFB cases, but in either instance, it must be completely removed. The first goal is to remove enough vitreous to remove all vitreous attachments to the foreign body. Although it is tempting to remove the foreign body as soon as it is seen, it is far better to complete the vitrectomy first. A big advantage of the vitrectomy approach is the avoidance of removal-induced vitreous traction. The need for a relatively complete vitrectomy before a foreign body removal is absolute.

Foreign Body Removal

It is not recommended that an extraocular magnet be used in conjunction with vitrectomy; the advantage of a slow, controlled removal without vitreous traction would be lost. Some surgeons have recommended intraocular magnets, but the authors have not used these devices because of the availability of the diamond-coated forceps. When all the vitreous around the IOFB has been removed, the superotemporal incision is enlarged to accommodate the largest outside diameter of the diamond IOFB forceps.

Moderately Sized Foreign Bodies

After the foreign body is grasped in the forceps and brought to the anterior vitreous area, its size can be better assessed. If the foreign body will not fit safely through the wound, but is not larger than 6 mm in its smallest diameter, the scleral wound should be enlarged with a knife (Fig. 23.2). It is best to plug the other sclerotomy so that the surgeon’s hand is free to enlarge the wound. A knife at the opposite end of the circumferential sclerotomy from the shank of the forceps should be used to extend the sclerotomy while stabilizing the other end of the wound with the shank of the forceps. Using this approach, it is not necessary to release the grasp of the foreign body, and a large, leaky incision need not be present while searching for and picking up the IOFB.

Figure 23.2 The free hand should use a diamond or disposable knife to enlarge sclerotomy for foreign bodies too large to go through 20-gauge microvitreoretinal (MVR) incision. This should be done after grasping the foreign body and bringing it near the pars plana to avoid a wound leak while grasping the IOFB.

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