Complete the vitrectomy
Partially illustrated in Fig. 2.14.3
Identify the site of the scleral wound or impact/exit site
The entire area must be visualized; use scleral indentation if necessary
Use the diathermy's highest power and completely surround the area5
The goal is not just to prevent bleeding but to destroy, necrotize, and burn away the retina and choroid.6 Use of a diathermy probe with a blunt, rather than a sharp, tip is recommended. A 1-mm ring of bare sclera should be left behind,7 but the scar itself remains intact. If the area of destruction were to involve the fovea, optic disc, or a major blood vessel, a sensible compromise regarding choroidal/retinal destruction would have to be sought
Surround the remaining retinal edge with laser
See Chap. 2.13 whether this is always necessary
Use gas or silicone oil tamponade
If complete vitreous removal has been achieved in the vicinity8 and bare sclera surrounds the scar, gas tamponade may be sufficient
3 A prospective, multicenter study (as suggested by W. Schrader, Würzburg, Germany) is now underway to evaluate the effectiveness of prophylactic chorioretinectomy in a much larger patient population (www.weironline.org). The study found that among its first 21
eyes, only 2 (10%) developed PVR; both were mild cases that were successfully treated.
4 The idea of prophylactic chorioretinectomy came to the author upon observing no PVR in eyes undergoing vitrectomy with removal of the choroid and retina in eyes with malignant melanoma. It appears that the proliferative cells do not bridge the bare sclera to seed the retina if the scleral bridge is wide enough.
5 Numerous small gas bubbles form during the procedure. In phakic eyes, these bubbles collect behind the lens if there is still vitreous there, making it easier and less risky for the surgeon to remove both the bubbles and the retrolental vitreous. In pseudophakic eyes the bubbles usually migrate away from the visual center.
6 The goal is not to cut the retina and choroid with scissors or the vitrectomy probe, but to use the diathermy's heat to actually destroy the entire tissue here.
7 i.e., the debris should be collected
8 The lesion is posterior to the equator.
The urgency to perform primary comprehensive surgery in an eye with rupture lies in the risk of retinal incarceration at the time of wound closure; the more posterior the wound, the higher this risk. In a perforating injury, the exit wound is rarely large enough to incarcerate the retina; the danger lies in events occurring postoperatively.
126.96.36.199 Intraoperative Wound Reopening 188.8.131.52.1 Risk Factors
The risk factors are as follows:
• Very fresh injury
• Older patient
• Significantly raised IOP (e.g., to stop an intraoperative hemorrhage).
Prevention consists of:
© Fig. 2.14.4 Schematic representation of IOP control during vitrectomy. a Traditional setup: the infusion bottle is directly connected to the eye through the infusion line. The IOP is regulated by up-or-down movements of the bottle, either electronically via the vitrectomy machine1 or manually. The problem with this setup is that the true IOP value is never known since there is no adjustment based on the distance of the patient's head (eye) from the floor. b If (a) the air pump of the vitrectomy machine is used to drive the pressure inside the infusion bottle, and (b) the drip chamber of the infusion bottle is at the same distance from the floor as the patient's eye, the air pressure set on the vitrectomy machine gives an accurate, digital reading of the actual IOP .
1 Newer machines even translate the bottle's distance from the floor to mmHg.
• Delaying vitrectomy until the posterior wound is firmly closed6
• Controlling and monitoring the IOP very closely during vitrectomy (Fig. 2.14.4)
The pathognomic signs are:
• Full-thickness sclero-chorio-retinal folds radiating from the wound
• Rapidly collapsing globe due to increased intraorbital pressure exerted on the posterior sclera
With regard to management:
• In the unlikely event that a posterior wound reopens during vitrectomy, the infusion must be turned off or at least significantly lowered so that additional fluid loss into the orbit is stopped.
• Silicone oil injection should be started as fast as possible, which reconstitutes the IOP and prevents further collapse of the eyeball. The amount of silicone oil implanted is usually half to two-thirds of the volume the eye would normally take.
6 As mentioned previously, the risk of wound reopening is much smaller if the injury is perforating, rather than a rupture.
• The orbital volume may be so greatly increased by the BSS (even silicone oil may be extruded into the orbit) that occasionally it is difficult to close the lids. In these rare cases the eye is treated as if temporary lagophthalmos were present.
• The orbital fluid rapidly reabsorbs, and a reoperation can be performed in a few days. It is also possible to suture the exit wound using an ab interno approach (J. Schmidt et al., unpublished data).
• try to verify whether the injury was penetrating or perforating
• if you are uncertain or if the injury is likely/definitely perforating, consider vitrectomy with prophylactic chorioretinectomy within the first few days post-injury
• try to suture-close an exit wound that is too posterior for convenient access
• panic in the unlikely case of intraoperative reopening of the exit wound: silicone oil implantation allows controlling the situation and the abandoned procedure can be completed in a subsequent surgery within days
Perforating injuries typically have very poor prognosis. Fortunately, in most eyes the outcome is poor not because the injury caused irreversible damage upon impact but because of subsequent scarring originating from the exit wound. Early prophylactic chorioretinectomy is a very promising procedure in preventing this complication and improving the functional outcome.
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