be done before irreversible conjunctival hydration occurs.

DESCEMET’S DETACHMENT

This is a potentially serious complication, which is often related to wound construction. The subject is covered fully in Chapter 23.

WOUND BURN

It is important for the surgeon to always be mindful of the potential for a wound burn. It can be observed by unusual bubble formation along the length of the phaco tip. In addition, whitening and distortion of the wound can be seen. If not immediately recognized, significant distortion of wound architecture ensues. Multiple tight sutures become mandatory to effect a reasonably watertight closure. Often, horizontal mattress sutures are better at approximating the roof and floor of the burned incision to create a watertight closure without the creation of large amounts of astigmatism. Sometimes wound closure becomes impossible, requiring a scleral patch graft or sliding scleral flap. Postoperative induced astigmatism due to wound distortion and the tight sutures may be significant.

The causes of wound burn are many. Some are poorly understood. They are:

1.The incision is too narrow or too long: As noted above, the crimped irrigation sleeve will impede inflow of cooling BSS. The phaco tip will then overheat and cause wound burn. The management of this potential problem is to enlarge the incision before a burn occurs.

2.Irrigating fluid deflection: When first inserting the phaco tip into the anterior chamber filled with dispersive viscoelastic, BSS inflow may be redirected and cause inflow to immediately pass out of the wound without cooling the tip. This will cause a wound burn on initiation of phaco. This potential problem can be managed by providing irrigation for a few seconds before applying phaco power at the beginning of the procedure. This will allow irrigation fluid to pass into the anterior chamber, thus averting a potentially serious complication.

3.Piezo-crystal control: In rare situations the software of the machine can become uncontrolled leading to overload of the piezo crystals. This will then overdrive the tip, creating dangerous heat and a severe wound burn. This malfunction is extremely rare and cannot be prevented. Once the burn occurs, the wound must be managed as noted above.

4.Tight wound: It is not uncommon to create a marginally narrow wound, especially in the clear

cornea. When this wound is exposed to highpower and prolonged phaco, as would occur with a mature nucleus, excessive heat may be generated and small wound burns may occur. In an effort to prevent this mild but annoying and astigmatism-generating problem, the irrigation fluid can be cooled prior to use. The BSS bottle is simply placed in a refrigerator at 40°F 1 day prior to surgery. The cool inflow effectively adds additional cooling capacity and prevents tip overheating. There have been no studies indicating the cool fluid is deleterious to the endothelium or other anterior chamber structures.

WOUND GAPE REPAIR

SLIDING FLAP TECHNIQUE

In situations where a primary closure is impossible subsequent to, for example, a wound gape due to scleral burn, or a buttonhole in the roof of the incision, a sliding graft is a possible closure alternative. This type of closure is difficult to perform when in the vertical or horizontal meridian in the vicinity of the superior rectus, or lateral rectus.

To create the flap, a limbus parallel incision 0.3 mm deep and 5 mm wide is created with the distal incision 5 mm posterior to the gaping incision and the proximal incision proximate to the gaping incision. The sclera is then undermined maximally (Fig. 4–5A). The flap thus created, still attached to provide vascular supply, is pulled down over the gape and sutured in place to seal the incision (Fig. 4–5B).

PATCH GRAFT TECHNIQUE

Should a wound gape occur to such a degree that closure primarily with sutures would induce inordinate amounts of astigmatism, or primary closure is impossible, a patch graft may become necessary.

The graft may be autologous. In this case the eye is rotated to expose the superiotemporal aspect. A large fornix-based pyritomy is created to expose superotemporal sclera. Incising the sclera to a depth of 0.3 mm creates a square or rectangular scleral patch of appropriate size. A lamellar dissection is then carried out to remove the patch. This is placed over the wound to cover the area of the gape. Four cardinal sutures of 10-0 nylon are then positioned. The patch is sutured firmly into place to create a watertight seal using a running 10-0 nylon suture. Conjunctival closure is then carried out with the same suture.

Banked sclera or processed pericardium can also be utilized rather than autologous tissue. It is

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