contact is not intermittent but permanent and the entire surface of the endothelium is involved), the development of band keratopathy is markedly delayed. This is why a phthisical eye needs to be made aphakic with a 100% oil fill,23 preferably with 5,000 cst oil (deferring emulsification, see above).

14.3.4 Complications Related to Silicone Oil Use Removal

•Oil sticking to the retina if during the original surgery PFCL was directly exchanged with heavy oil: an easily avoidable problem.24

•RD, occurring in up to a fifth of the cases (see Sect. 35.4.6).25

•VA loss upon silicone oil removal: a fortunately rare occurrence. Why vision drops after oil extraction and does not recover remains a mystery.

14.4PFCL

Unlike the true tamponades, the heavy fluid is an intraoperative tool, not intended to be retained after PPV. It is an extremely useful “third hand” in many situations, but it should not be overused (see Table 14.4).

Complications:

•PFCL has a high tendency to evaporate.

–The nurse should not keep it in an open container or it will rapidly disappear “into thin air.”

–This evaporation is the reason why, upon intraocular injection, it is virtually impossible to avoid implanting a small air bubble into the vitreous, even if the nurse carefully pushed all the air out of the cannula.26 This bubble is usually stuck to the anterior (i.e., superior) surface of the enlarging PFCL bubble and remains centrally located (see Fig. 33.1).

–In the air-filled eye, the evaporation continues: small bubbles gather on the back surface of the posterior capsule/IOL. This interferes with visualization (the bubbles can easily be aspirated but will reaccumulate if the air is not replaced with fluid) and causes loss of PFCL in the back where it would be needed.

•A PFCL bubble inadvertently left in the subretinal space is potentially toxic. Unless it is under the fovea, however, it is not justified to perform surgery just to remove the bubble.

23The oil is in permanent contact with the endothelium, making it impossible for the little remaining aqueous to enter the corneal stroma. Even then, corneal complications are inevitable.

24A hyperviscous solution that makes subsequent silicone oil removal very difficult. It is best to prevent this by exchanging the PFCL to air first, not directly to heavy oil.

25The figure depends on many factors such as the original indication, the type and quality of the original and subsequent surgeries, and intraocular events since the last operation.

26Caused by the evaporation of the PFCL from the inside of the cannula used for the injection.

•The channel (suture track) created by the needle is always larger than the suture material that occupies the channel.

–Intraoperative leakage along the track in case of a 100% deep corneal suture (see Fig. 63.2b) is therefore unavoidable, but this ceases as the tissue swelling compresses the channel.

•Do not grab the cornea when suturing it (see Table 63.3).

–It is unnecessary because the needle is sharp enough to enter, pass through, and exit the tissue: it will not push the tissue away.29

•All sutures work by tissue compression. In most tissues, there is no untoward consequence of too much compression.

–In the cornea, too much compression results in tissue deformation, which distorts the view for both patient and ophthalmologist.

•In the cornea, all suture knots must be buried.

–Too large a knot makes it impossible to pull the knot into the suture channel.

–The suture should be cut short.

Pearl

A blade is preferred over scissors to cut the thread (Fig. 14.6). This gives the surgeon more control by increasing the visibility (the scissors may block the view) and precision (the suture is moved to the blade, not the other way around).

Even if the VR surgeon never in his life needs to place corneal sutures,30 closing scleral wounds will surely be necessary in MIVS or trauma (see Sects. 21.8.3 and 63.5).

Q&A

Q When do you have to close the sclerotomy in MIVS?

AThe default option is not to use sutures – this is what makes small-gauge PPV more comfortable for the patient than the traditional 20 g option. However, if the wound is leaking or silicone oil is used, it is advisable to suture-close it to avoid postoperative hypotony or subconjunctival displacement of the oil.

To close a sclerotomy, typically 7/0 vicryl (or silk) is used. The former is absorbable31; the latter is not, which is a strong argument in favor of the former.

29In all other tissues, the resistance against the advancing needle is high so the tissue tends to move with the needle in the same direction. The forceps is employed to counteract this movement: the surgeon pulls the tissue against the movement of the needle.

30Which is indeed difficult to imagine.

31I.e., the vicryl suture does not require removal, irrespective of whether it is in the conjunctiva or sclera.

The difficulty of closure comes from the fact that many times neither the conjunctival nor the scleral wound is visible.

•If silicone oil has been used:

–The surgeon grabs, with his nondominant hand, the sclera with teeth forceps,32 and lifts the sclera slightly up.

–The surgeon removes the cannula with his other hand.

–The nurse places the needle holder into the surgeon’s outreached palm, making sure that the needle is facing the correct direction (away from or toward the surgeon, see Fig. 54.7).33 Meanwhile the surgeon keeps the wound lips pressed together with his nondominant hand.

–A double loop is created so that the incision is instantly closed when the suture itself is pulled up (Fig. 14.3).

If the scleral wound is not visible because of bleeding or chemosis, the conjunctiva may have to be incised.

32A colibri-type forceps with small teeth is the most optimal option.

33Another example of why a good nurse is so important.