device is that it can be easily placed through the phaco incision, and everything can be cleaned up without much instrument manipulation and general confusion. Unfortunately, due to fundamentally poor instrument design, small amounts of vitreous prolapse often become large amounts of vitreous loss. What was anticipated to be only a few seconds of vitrectomy cutting turns into several minutes, as vitreous removal seems to be never-ending.

The coaxial infusion cannula fails because it violates the prohibition against stretching the Slinky in three ways:

1.When the coaxial vitrectomy tip is placed into the eye, the infusion eventually strikes the posterior capsule. This force can stretch or tear the capsular opening, increasing its size. Up to this point, the limited hole in the posterior capsule restricted the volume of vitreous that could come forward. The intact surface of the posterior capsule serves as a membrane barrier, blocking vitreous movement and restricting further loss of vitreous. When the infusion rips apart the opening in the capsule, the barrier effect is reduced, and there is more room for the vitreous to come forward. The greater the vitreous loss, the more the Slinky is stretched (Fig. 19–3A).

2.Once the coaxial cannula reaches the body of the vitreous, infusion fluid hydrates the vitreous, increasing its volume. The walls of the eye successfully confine vitreous extension in any direction except toward the anterior chamber. The forward movement of vitreous, due to its increased volume, stretches the Slinky (Fig. 19–3B).

3.Finally, the infusion pours into the vitreous cavity. The flow moves the vitreous around, wiggling it and shaking it and flushing it toward the anterior chamber. This is why what often starts off as a

fairly minor vitrectomy can turn into a rather lengthy procedure. Vitreous that was in its normal position, and quite frankly, sitting where it ought to sit, is now removed from its proper location and brought to the anterior chamber instead. The flushing of vitreous from the eye may well be one of the most traumatic consequences of the vitreous loss/vitrectomy process. This really stretches the Slinky. Vitreous that was passively intact at critical spots inside the eye is now wiggled and thrust about from the infusion, disturbing the vitreomacular interface and the vitreous base (Fig. 19–3C). The way to avoid stretching the Slinky is to eliminate the use of the coaxial infusion cannula and to use the vitrectomy tip naked, without a sleeve. Infusion will come from another source.

MAKING A NEW INCISION

PERFORMING THE VITRECTOMY

TWO-HANDED

The vitrectomy tip with the coaxial infusion cannula could be placed through the standard phacoemulsification incision. If we use a vitrectomy tip without the cannula, it will necessarily be much thinner. If it is placed through the larger phaco incision, there will be a fair amount of fluid egress around the tip. This outflow current is especially dangerous because vitreous can be caught in it and pulled to the incision. Vitreous will be trying to escape from the eye, stretching the Slinky (Figs. 19–4A and 19–5A).

This produces a common finding. Following what appears to be a routine vitrectomy there is a vitreous strand through the incision that needs to be swept down using a spatula at surgery or requires yttrium- aluminum-garnet (YAG) vitreolysis postoperatively.

Fishkind4 reported this occurrence in 33% of vitrectomies. Actually, in many cases, getting the vitreous away from the posterior capsule is the easy part; getting it away from the incision is much more difficult.

The vitrectomy tip should not be placed through the primary phaco incision because the incision is the wrong size for it. Instead, the eye should be made firm with viscoelastic and then a new 1-mm stab incision should be made a few millimeters away from the main phaco incision. Now there will be an incision that is exactly the right size for the vitrectomy tip and

another one, the original side port incision, the correct size for the chamber maintainer. The pressure in the anterior chamber from viscoelastic or chamber maintainer irrigation will close off the self-sealing corneal, or sclerocorneal, incision previously used for phacoemulsification (Figs. 19–4B and 19–5B).

Another portal of entry for the vitrectomy instrument is the pars plana. A small conjunctival peritomy is performed 3 mm from the limbus and bipolar cautery is utilized to attain hemostasis. Using a lance type of blade [massive vitreous retractor (MVR)

blade], a sclerotomy opening is made by pointing the tip of the blade toward the optic nerve. It is necessary to visualize the blade within the pupillary space before extracting it. Using a butterfly needle, an anterior chamber maintainer, or some other type of infusion through the paracentesis anteriorly, a posterior vitreous cutter (without an irrigation sleeve) is placed through the sclerotomy and vitreous is accessed easily from within the pupillary space and in the subincisional area (see Chapter 30, Fig. 30–5). Small capsular tags can also be removed but care should be taken to retain as much capsule as possible. Once the vitreous has been removed and the anterior segment swept with a cyclodialysis spatula, to be sure that no residual vitreous is present, the sclerotomy site can be closed using an X 10-0 nylon suture.

Once the vitrectomy instrument is placed through the paracentesis or pars plana, the eye is converted to a closed system. There are only two incisions and both are the correct size for the instruments being used; the larger incision has been sealed shut. The closed system is the most effective way to perform a vitrectomy. This is best illustrated by the pars plana closed system used by vitreoretinal surgeons.

When the new smaller incision is used for vitrectomy, the procedure is performed rapidly and conveniently. Vitreous has virtually no tendency to go to any of the incisions and the procedure can be performed with great precision.

PERFORMING THE VITRECTOMY

WITHOUT IRRIGATION

This is a useful technique in performing a small vitrectomy. The vitrectomy tip should be placed just below the level of the posterior capsule, with the aspiration port directed up toward the cornea. Cutting is activated followed by a little bit of aspiration without cutting. The vitreous in the anterior chamber is pulled down to the vitrectomy tip. All of the vitreous below the vitrectomy tip is left alone (Fig. 19–6).

If the eye softens, the pressure in the eye can be equalized by putting more viscoelastic into the anterior chamber, which has the added effect of pushing vitreous toward the back of the eye and reducing the amount of vitrectomy that has to be performed.

PERFORMING THE VITRECTOMY

WITH IRRIGATION

Alternatively, a chamber maintainer can be placed in the side-port incision, filling the anterior chamber with fluid to replace volume removed with the vit-

FIGURE 19–6 A new incision is made a little to the right of the phaco incision for the vitrectomy tip. The chamber maintainer is in the original side port incision. The phaco incision closes spontaneously. There is now a closed system for the vitrectomy.

rectomy. The irrigating fluid might hydrate the vitreous in the anterior chamber, but this is acceptable because that vitreous is going to be removed anyway. We just do not want the fluid to hydrate much of the vitreous below the vitrectomy tip. This is avoided by keeping the infusion cannula parallel to the iris, so that the infusion is directed into the anterior chamber and the vitrectomy tip can remove the fluid before it escapes into the body of the vitreous.

Once the vitreous is removed below the level of the posterior capsule, the vitrectomy is stopped. There is no need to remove any further material because the remainder of the vitreous is where it ought to be, that is to say, in the posterior segment where it has been for the patient’s lifetime. Remember that the purpose of the vitrectomy is to remove only the offending vitreous that is on stretch and that has become anterior to the posterior capsule. Once that vitreous has been removed, the process is complete. There is no reason to continue (Fig. 19–7).

At this point viscoelastic is placed in the eye. An intraocular lens of choice is placed into the anterior chamber, and then dialed or placed into the ciliary sulcus. The increased surgical time required by the vitrectomy is only a few minutes. The postoperative course should not differ from that of an uncomplicated case.

POSTOPERATIVE CARE

It has been reported that approximately one-third of patients requiring vitrectomy will have elevated intraocular pressure.4 One can speculate that the additional intraoperative manipulation may cause addi-

tional postoperative inflammation. Therefore, these problems should be anticipated. At the conclusion of the case it is beneficial to perform a subconjunctival injection of betamethasone sodium phosphate and betamethasone acetate 6 mg/m (Celestone) 1 mg to provide a short acting antiinflammatory pulse and triamcinolone (Kenalog) 20 mg for its sustained antiinflammatory action.

DROPPED NUCLEUS

There is one exception to the rule about keeping the posterior capsule as intact as possible to limit vitreous prolapse. That occurs when a large piece of nucleus falls into the posterior segment and the surgeon wants to try to recover it (see Chapter 26). The posterior capsule and, for that matter, the anterior capsule serve as a barrier holding the nucleus back. For the nucleus to be lifted into the anterior chamber, both the posterior capsule and the anterior capsule have to be opened to permit its passage. The amount of the opening will depend on the size of the nucleus, but in general, the larger the opening the better. A rim of anterior capsule left intact will facilitate placement of a posterior chamber implant in the ciliary sulcus.

CONCLUSION

one that is easily handled. By remembering the motto, “Don’t stretch the Slinky” surgeons will be able to limit the amount of vitreous that is displaced, remove it as gently as possible, and minimize the likelihood of developing postoperative complications.

REFERENCES

1.Fishkind WJ. Unexpected vitrectomy as a complication of cataract surgery. J Cataract Refract Surg 1994; 20:54–57.

2.Osher R, Cionni R. The torn posterior capsule: its intraoperative behavior, surgical management, and long-term consequences. J Cataract Refract Surg 1990; 16:490–494.

3.Powe NR, Schein OD, Gieser SC, et al. Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation. Arch Ophthalmol 1994;112:239–252.

4.Fishkind WJ. The torn PC mechanisms and outcomes. Presented at the American Society of Cataract and Refractive Surgeons annual meeting, Seattle, April 1999.

5.Matoltsy AG. A study on the structural protein of the vitreous body (vitrosin). J Gen Physiol 1952;362:29.

6.Sebag J. Vitreous biochemistry, morphology, and clinical examination. In: Thomas D, ed. Clinical Ophthalomolgy. Vol. 3. Philadelphia: Lippincott Williams & Wilkins; 1998:7–15.