Introduction to Small-Gauge |
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Vitrectomy |
1.1History
Since the 1970s, 20-gauge vitrectomy has evolved as the worldwide standard for vitreoretinal surgery. All instruments have a lumen diameter (inside diameter) of 0.9 mm. For this procedure, the conjunctiva is opened, three sclerotomies are placed and the infusion cannula is sutured to the sclera. In the majority of cases, trocar cannulas are not used and at the end of the surgery, the sclerotomies are sutured.
In 2002, Eugene de Juan et al. introduced 25-gauge vitrectomy. The instruments had a lumen diameter of 0.5 mm. Trocars (cannulas) were used for the infusion and the instruments. The trocars were inserted transconjunctivally and transsclerally and remained in place during the entire surgery without the need for suturing them to the sclera. A major advantage of this new technique was the reduced anterior segment trauma during the procedure because the conjunctiva is not opened and the instruments are smaller. One disadvantage was an increased risk for postoperative hypotony due to the absence of sutures. Another disadvantage was that the instruments were very flexible and not all instruments could be produced in such a small diameter. Meanwhile, more rigid instruments were developed that proved to be easier to handle. The 25-gauge technology is particularly popular in the United States.
In 2004, 23-gauge vitrectomy with a lumen diameter of 0.65 mm was developed at the Eye Clinic FrankfurtHöchst by Prof. Dr. Claus Eckardt. In 23-gauge vitrectomy, the benefits of 25-gauge vitrectomy (transconjunctival trocar, no suture, reduced surgical trauma) are combined with the advantages of the 20-gauge technology (rigid instruments, more efficient vitrectomy, easy accessibility of the vitreous base) (Figs. 1.1 and 1.2). Finally, a new incision technique was developed: The sclerotomies are performed in a lamellar fashion (tunnel technique), which results in a better postoperative wound closure and less postoperative hypotony.
The latest development is 27-gauge vitrectomy. The instruments have a diameter of only 0.4 mm. The company DORC has the 27-gauge vitrectomy with trocars in their product range. However, the indication spectrum for this technique is very limited. Possible indications are, for example, vitreous opacities or a central vitrectomy in the newborn.
U. Spandau, H. Heimann, Practical Handbook for Small-Gauge Vitrectomy, |
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DOI 10.1007/ 978-3-642-23294-7_1, © Springer-Verlag Berlin Heidelberg 2012 |
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1 Introduction to Small-Gauge Vitrectomy |
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Fig. 1.1 An intraoperative image of a retinal detachment surgery with 4-port technique: the infusion line at the top right and the fixed fibre optic chandelier at the top left. Left and right below the two instrument trocar cannulas
Fig. 1.2 A postoperative image of the same detachment surgery: you can recognize the implanted intraocular lens and the almost white conjunctiva. A 20% SF6 tamponade was used
1.2Key Features of ‘Micro-Incision Vitrectomy Surgery (MIVS)’
The techniques of 23-gauge and 25-gauge vitreoretinal surgery are also referred to as ‘micro-incision vitrectomy surgery’ (MIVS). The 23-gauge vitrectomy as well as 25-gauge techniques can now be used for more challenging posterior segment surgeries, including PVR retinal detachment and diabetic vitreoretinopathy with silicone oil. The main features are:
•Lamellar and sutureless sclerotomies
•Trocar cannulas
•Bimanual surgery
1.2 Key Features of ‘Micro-Incision Vitrectomy Surgery (MIVS)’ |
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Fig. 1.3 This histological section of an eye showing a lamellar cut through the sclera for 23-gauge vitrectomy. This tangential cut needs no suture. It is comparable to the tunnel cut in phacoemulsification
Fig. 1.4 23-gauge trocar with blue valve and blunt insertor. This model is from DORC. Other manufacturers such as Oertli or Geuder also offer trocar cannulas with valves
1.2.1Sutureless Sclerotomy
The sclerotomies are performed with a tangential incision (lamellar tunnel incision), i.e. the sclerotomy is self-sealing and does not require suturing (Fig. 1.3).
1.2.2Trocar
A trocar is a metal or plastic cannula which is placed transconjunctivally in the sclerotomy. The trocars are not sutured and remain in the sclerotomy during the entire surgery (Figs. 1.4 and 1.5).
The trocar system is an essential part of the MIVS. It significantly lowers the anterior segment trauma and is associated with minor postoperative discomfort. Table 1.1 lists the advantages and disadvantages of the trocar. 25-gauge is superior to 23-gauge concerning the sclerotomy closure and the speed of postoperative recovery. A suture is sometimes necessary for 23-gauge sclerotomies but very seldom for 25-gauge sclerotomies. These characteristics are especially interesting for minor surgeries such as macular peeling.
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1 Introduction to Small-Gauge Vitrectomy |
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Fig. 1.5 Trocar forceps for handling trocars, e.g. insertion of the infusion line. DORC. 1276.2
Table 1.1 Advantages and disadvantages of the trocar system
Advantages |
Disadvantages |
Tangential incision (lamellar tunnel) at the |
Postoperative hypotony |
sclerotomy |
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No suture required |
Angled instruments do not fit through trocars |
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Trocar may be dislodged during removal of |
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instruments |
Trocar openings easier to find for instrument |
Raised trocar openings may be covered by lids |
insertion than conventional sclerotomies |
in patients with small lid apertures |
No extensive opening of conjunctiva |
Transconjunctival vitreous prolapse (‘vitreous |
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wick’) |
Trocars with valves enable a closed system |
Higher intraocular pressures during injection |
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of gas or fluids |
Less foreign body sensation |
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Low corneal astigmatism |
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Faster postoperative recovery |
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Rapid visual rehabilitation |
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1.2.3Bimanual Surgery
During conventional vitrectomy procedures, the surgeon holds the light pipe in one hand and the vitreous cutter or a different ‘active’ instrument in the other hand (Fig. 1.6). In challenging situations, a more active second hand other than holding the light pipe can be useful. By inserting a fixed light probe (chandelier) in the sclera through a 4th sclerotomy port, the surgeon is enabled to use both hands actively (Fig. 1.7). The chandelier light illuminates the entire posterior segment with a panoramic view. Now, procedures such as indenting the retina and simultaneously performing a vitrectomy or bimanual peeling of membranes in PVR retinal detachment or diabetic retinopathy are easier to perform.
1.2 Key Features of ‘Micro-Incision Vitrectomy Surgery (MIVS)’ |
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Fig. 1.6 An example of an operation with a 3-port trocar system. One infusion cannula and two instrument cannulas have been inserted. A handheld light pipe is used as a light
Fig. 1.7 An example of a surgery with a 4-port trocar system. In the 4-port trocar system, the fourth sclerotomy is used for a fibre optic chandelier, enabling the surgeon to work with two free hands. Synergetics. 25-gauge Awh Chandelier 56.20.25
Other advantages of the 23-gauge vitrectomy compared to the 20-gauge vitrectomy are:
•Significant reduction of overall surgery time (no opening of conjunctiva, no sutures, and no cauterization of bleeding vessels)
•Protects sclerotomies when inserting instruments
•Easier to find the sclerotomies
Bias against 23-gauge vitrectomy:
•A persistent and widespread opinion concerning 23-gauge surgery is that the use of silicone oil is not possible or difficult. This is not correct. A silicone oil tamponade with 1,000 cSt silicone oil and its removal can easily be performed
•A further notion is that the removal of the vitreous takes longer compared to 20-gauge systems
In the meantime, this disadvantage has been overcome by the introduction of
new high-speed cutters.