The indications for secondary vitreoretinal repair are media opacity such as vitreous hemorrhage, vitreous and/or retinal incarceration in a sclera wound, and/or retinal detachment. Perforating injuries usually have a combination of these findings. The main goals are to (1) remove as much vitreous as possible to clear the globe of the scaffold for fibroproliferation, with special attention to the transvitreal tract between the entry and exit wounds, and the vitreous attachments to the wounds; (2) remove vitreous hemorrhage, which is an most important risk factor for subsequent PVR;[8,17] and (3) reattach the retina.
Most agree that vitrectomy should take place within 2 weeks to clear the globe of hemorrhage, inflammation, and the vitreous scaffold, before the initiation of intense PVR. There are 2 schools of thought: early vitrectomy within 1 to 3 days, and delayed vitrectomy between 7 and 14 days,[1,19] and the latter period is now the standard of care.
From a historical perspective, Coleman described 3 windows for surgical intervention: "The first window occurs after injury, but before the development of inflammatory sequelae. At this point, removing the entire vitreous is generally unnecessary. Only the disrupted lens, blood, and vitreous must be removed." The argument for early vitrectomy is to remove all proinflammatory factors before fibrosis can initiate. The counterargument is that operating on an acutely traumatized eye can have unpredictable findings with higher likelihood of continued hemorrhage. Choroidal hemorrhages also have not undergone liquefaction, making drainage difficult. Vitrectomy is also more challenging because a spontaneous PVD usually has not formed yet during this first window, especially in young patients.
The second window is from 7 to 14 days. "Once the inflammation is controlled or the originally lacerated vessels have healed, or both, a second window appears before the full development of organized fibroproliferative membranes." The membranes are still easy to peel and cut during this phase, and traction, if any, can be relieved without much difficulty. A PVD would have usually formed by this window, which facilitates the vitrectomy. However, a lack of a PVD should not deter one from proceeding with the vitrectomy. The vitreous does need to be completely removed by this stage. Waiting for this period after the primary repair also allows a more thorough examination with ultrasonography to determine whether the eye is salvageable based on the intraocular anatomic status. Almost all vitreoretinal surgeons typically wait for this 7- to 14-day window.
"A third window often occurs if and when the acute hemorrhagic and inflammatory stages have subsided. Surgery is then indicated primarily for optical reasons, that is, providing an opening in the anterior cyclitic structure or posterior vitreous hyaloid complex or both." Fibrovascular proliferation and panopthalmic sequelae of inflammation have often created tractional changes by this stage. This third window may be narrow, and should be avoided if possible, as the patient is at risk for tractional retinal detachment and retinal tears while waiting for surgery.
Pars Plana Vitrectomy Trauma cases are complex and unanticipated intraoperative findings commonly occur. The standard 3-port vitrectomy is usually performed. The intraocular pressure is closely monitored, because high pressures could cause retinal extrusion through the exit wound. Efforts should be made to keep the pressure <30 mm Hg.
If the lens was not lost or removed during the primary repair, indications for lensectomy at this time would be grossly violated capsules, poor visualization from traumatic cataract or tightly adherent blood on the lens, lens subluxation or dislocation, cyclitic membranes, transvitreal fibrosis with anterior extension, or any substantial posterior segment pathology. Lensectomy allows complete removal of the anterior vitreous and eliminates the scaffold for anterior PVR. Our philosophy is that no eye has ever gone blind from aphakia. Therefore, in severe trauma cases, if lensectomy (including removal of capsule) will improve the chances for long-term retinal reattachment, then the lens should be removed. A fragmatome is used to sculpt the lens in older adults, and younger adults and children may only require the vitrectomy cutter. Peripheral capsular remnants can be grasped with forceps and pulled centrally into the pupillary space, whereas the vitrectomy cutter is used to remove the capsule and zonules.
A core vitrectomy is first completed to remove vitreous debris, and then a PVD is induced, if the posterior hyaloid is still adherent to the retina, by turning the cutter off and engaging the vitrectomy aperture by the peripapillary posterior hyaloid and aspirating gently. Soft-tipped extrusion cannulas or picks can also be used. The PVD is then extended to the periphery. The vitreous base should be shaved using sclera depression.
A crucial step in perforating injuries is to remove the vitreous from the entry and exit wounds. Vitreous incarceration is a risk factor for poor outcomes from PVR. Care should be taken to reduce the fibrovascular proliferation at the exit wound until it is flush with the retina, but not to eliminate it completely, to avoid risks of hemorrhage and wound dehiscence.
Retinal Incarcerations If there are tractional retinal detachments, every effort should be made to relieve all tangential and anterior-posterior traction by membrane peeling. Traumatic retinal detachment is discussed in another review in this issue.
Retinal wound incarceration can create challenging retinal detachments with poor visual prognosis. Retinal incarceration at the time of initial injury is rare in perforating injuries when compared with blunt ruptures, because the latter usually has much larger defects and more tissue expulsion. However, the fibrovascular proliferative response usually incorporates the exit wound, and the retina can become incarcerated during this process.
In many cases, scleral buckling is essential in relieving the traction at the incarceration site. A circumferential relaxing retinectomy along the posterior margin can be created if the buckle alone does not completely release the traction for incarcerations at the equator or more anteriorly. If the incarceration is too posterior to be supported by a scleral buckle, retinotomies circumscribing the incarceration margin can be made. The retinotomies should be large enough to relieve traction, but as small as possible. The edges are then photocoagulated. Retinectomies and retinotomies should be performed only when necessary, because subsequent PVR can reopen the retinal defects.
In Han et al's review of vitrectomy for 15 eyes with traumatic retinal incarceration, 6 eyes achieved 5/200 or better. Six of 7 eyes with incarcerations posterior to the vortex vein ampullae had anatomic reattachment, but only 2 eyes had 5/200 or better. Of the 8 eyes with anterior incarcerations, anatomic reattachment was achieved in 5 eyes, and 4 eyes had 5/200 or better.
PVR PVR is the most common cause of operative failure and vision loss after primary repair. The frequencies of PVR after vitrectomy for perforations, ruptures, penetrations, intraocular foreign bodies, and contusions were 43%, 21%, 15%, 11%, and 1%, respectively, in a series of 71 patients from Doheny Eye Institute. Other studies have reported rates of PVR after vitrectomy for perforating injuries to be as low as 14%, to as high as 62%.
The management of PVR follows the principles of conventional retinal detachment surgery: identify all retinal breaks, release traction, and reattach the retina. Extensive PVR may not allow all of the breaks to be initially identified, but this becomes more feasible as traction is gradually released. Preretinal membranes are dissected before subretinal bands, because the former usually accounts for the majority of tractional changes. If immature membranes cannot be grasped adequately with forceps, they can be stroked with a silicone tip or diamond-dusted silicone cannula.
If there is still traction from subretinal membranes after preretinal traction has been released, the subretinal space can be accessed by a retinotomy to grasp the membranes. The subretinal strands can be pulled gently, or rolled around the forcep like spaghetti to mobilize the bands without breaking them. The most difficult subretinal membranes to remove are the annular napkin-ring configurations. Retinectomies are often required for direct exposure of these membranes.
Anterior PVR is difficult to manage. There is often a fibrous circumferential membrane adherent to the pars plana or ciliary processes. First, the anteroposterior traction that displaces the retina anteriorly is relieved by creating an opening in the membrane by an microvitreoretinal blade or the vitreous cutter. This opening is then extended circumferentially with vertically cutting scissors or the vitreous cutter. If traction persists, it is from circumferential traction, which can be released with vertical sections.
Retinectomy is indicated if the retina has been foreshortened and would not flatten even with meticulous membrane peeling. Hemostasis is essential in perforating injuries because any amount of hemorrhage can contribute to further PVR. Retinotomies and retinectomies therefore should be made over diathermy burns.
If perfluorocarbon liquids (PFCL) are used, posterior membranes are dissected first to flatten the retina and allow stabilization of the posterior pole for anterior dissection. Conversely, if PFCL is not used, anterior membranes should be dissected first while the posterior retina is stabilized from the PVR. Of note, traction surrounding any retinal breaks should be released before PFCL makes contact with the area, to avoid PFCL from entering the subretinal space. Retinal slippage can occur during PFCL removal during air exchange if there is a large retinectomy. To avoid this, the fluid anterior to the PFCL is first exchanged for air, and any remaining fluid behind the edge of the retinectomy that can migrate posteriorly is aspirated with a soft-tipped cannula.
Long-term retinal-RPE attachment is promoted by endophotocoagulation of the retinectomy/retinotomy margins. Care should be taken to assure that the retina where the laser will be applied is completely free of tractional forces, because it could lead to further breaks and holes. Prophylactic 360-degree endolaser can also be performed.
Tamponade and Retention Sutures Gas or silicone oil tamponade is recommended for perforating injuries. Silicone oil is the preferred agent for eyes at high risk of developing PVR, especially if there are inferior retinal breaks or an inferior retinectomy. The Silicone Oil Study found that in the management of severe PVR, silicone oil was superior to SF6, and equivalent to C3F8 in eyes without previous vitrectomy.[24,25]
Pupillary block and silicone oil prolapse into the anterior chamber can cause glaucoma and corneal endothelial damage. An inferior peripheral iridectomy can be made in aphakic eyes with an intact iris. In aphakic eyes with partial or complete iris loss, silicone oil retention sutures may be placed before oil injection. 10–0 prolene sutures are placed across the anterior chamber from sulcus to sulcus at the level of the previous iris diaphragm, to form a square or triangle centered on the visual axis. Interweaving the sutures has allowed accurate alignment of the sutures for best retention. Areas with scleral thinning can be avoided by creating different configurations. Oil retention sutures will not be effective if the eye develops hypotony.
Intraoperative Wound Dehiscence Intraoperative dehiscence of the exit wound is a rare event that should be prevented if possible. Signs of dehiscence include a rapidly collapsing globe, and full-thickness folds of the sclera, choroid, and retina, radiating from the wound. The risk factors for wound reopening include large wounds, fresh injuries, older patients, and elevated intraocular pressures. Delaying vitrectomy until the exit wound is sealed and avoiding high intraocular pressures during vitrectomy are preventive measures.
Successful management of exit wound dehiscence relies on early detection, quick silicone oil tamponade, and temporary abandonment of the surgery. The infusion is first lowered or stopped to decrease fluid extrusion into the orbit. Silicone oil is then injected to correct the hypotony and to reinflate the globe. Only about a half or two thirds that the eye would usually require is sufficient for this purpose. The orbital contents will become swollen from the extruded balanced salt solution and silicone oil, and lid closure may become impaired. However, the orbital fluid will be rapidly reabsorbed, and surgery can be reattempted in a few days.
Prophylactic Scleral Buckles etinal detachment develops in approximately half to two thirds of posterior segment penetrating injuries and is associated with poor prognosis. Peripheral retinal traction is common because complete shaving of the vitreous base is difficult, and the risk of PVR is high. A preplaced anterior buckle can therefore decrease traction that may subsequently form. Prophylactic buckling is sometimes placed for perforating injuries, due to the even higher risk of PVR. The timing of buckle placement is not well defined for either penetrating or perforating injuries. The buckles may be placed either during the primary repair or at the time of delayed vitrectomy.
Routine placement of scleral buckles at the time of primary repair is easier than during the surgery 7 to 14 days afterward, because there is no postsurgical scarring, and the fibrosis between the wounds and overlying Tenon's capsule is still limited. However, for perforating globe injuries, securing bands on the exit wound may be challenging for the ophthalmologist without vitreoretinal training. Prophylactic scleral buckle at the time of delayed definitive ocular reconstruction in posterior penetrating globe injuries has been examined by more studies, and it seems to decrease the occurrence of late retinal detachments.[30,32,33]
Int Ophthalmol Clin. 2013;53(4):127-137. © 2013 Lippincott Williams & Wilkins