4.2Pars Plana Vitrectomy Step by Step

In the following section, a standard pars plana vitrectomy is explained. As in a cookbook, the ingredients (instruments, dyes, tamponade) are listed first and then the practical approach is explained in detail step by step.

Instruments

1.3-port trocar

2.120D or 90D magnifying glass

3.Light pipe

4.Vitreous cutter

5.Scleral depressor

6.Fluid needle

Dye

Triamcinolone

Tamponade

Air, gas, silicone oil

Individual steps

1.Insertion of trocar cannulas

2.Phacoemulsification

3.Focussing

4.Core vitrectomy

5.Induction of posterior vitreous detachment

6.Trimming of vitreous base

7.Anterior vitrectomy

8.Internal search for retinal breaks

9.Laser photocoagulation of peripheral breaks

10.Cryotherapy of peripheral breaks

11.Intraoperative tamponade

12.Postoperative tamponade

13.Removal of trocar cannulas

14.Sclerotomy sutures

1.Insertion of trocars

The sclerotomies must be placed in the pars plana (there is no retina). The distance

DVD

Video 1 Insertion of trocar cannulas

of the sclerotomies to the limbus is 3.5 mm in pseudophakic eyes and 4.0 mm in phakic eyes (Table 4.1). By using a scleral marker, you can measure and mark the sclerotomy. It is recommended that you always (even after the beginner phase) use

Fig. 4.4 The left hand inserts the trocar exactly in the puncture site marked

by a bleeding

Fig. 4.5 The eye should look like this after insertion of the trocars. Note: The trocars for the instruments are located at 2:00 till 2:30 and 9:30 till 10:00

Fig. 4.6 An eye after removal of all trocar cannulas. We see no leakage (no air or fluid under the conjunctiva in the area of sclerotomies).

A suture is not necessary

used trocar systems can be divided into two groups: one-step and two-step systems. A one-step system uses a sclerotomy knife inside the trocar. Similar to a venflon cannula, trocar and knife are introduced in one step; the knife is then withdrawn, and the trocar remains in the sclera. With the two-step approach, the sclerotomy is made with a sclerotomy knife, and in a second step, the trocar is introduced through this opening. The advantage of the one-step system is that it simplifies the introduction of the trocar, as one does not need to search for the sclerotomy site, in particular if the conjunctiva has been ballooned through the local anaesthetic or during previous phacoemulsification. Further, there is no danger of pushing conjunctiva through the sclerotomy. The disadvantage of the one-step system is that the knife usually is not as sharp as the ones used for the two-step approach. The resulting sclerotomy wounds are usually slightly more irregular than the ones created by the two-step knifes and, therefore, may not seal as well. This may lead to postoperative hypotony and loss of tamponade, in particular with the 23-gauge systems. It has to be said, however, that the latest generation of one-step knifes have improved immensely compared to previous models. Therefore, more and more surgeons are now switching to one-step systems.

Pits & Pearls No. 7

Choose the position of sclerotomies wisely. Try to place your hands in a comfortable position, mimicking your working position in order to identify the best position for your sclerotomies before inserting the trocars. The standard position is 4 o’clock (left) or 8 o’clock (right) for the infusion and 9:30–10 and 2–2:30 o’clock for your working ports. See Diagram 4.1. The best position for the chandelier light is inferonasally because only in this position it does not interfere with the rotation of the globe. In phakic eyes, we recommend that you move your working ports closer to the 3 and 9 o’clock positions. This way, you have a better angle to trim the vitreous base at 12 and 6 o’clock with a lower risk for lens touch.