The Speculum and Its Placement |
19 |
|
The function of the speculum is to keep the lids securely apart during the operation and to prevent the eyelashes from contaminating the operative field (see Sect. 18.1).
19.1General Considerations
•As opposed to cataract surgeons,1 VR surgeons strive for opening the lids as wide as possible to provide unobstructed access to the front surface of the eye.
–The lids’ normal (default) position works against the intended purpose of the speculum.2
Pearl
The selection of the proper type of speculum does not seem to be an important issue until the surgeon is forced to struggle with it intraoperatively.
–If the lids are not widely separated, the visco may get wiped off the corneal surface as the surgeon rotates the eye.
–Conversely, if the patient’s orbital fissure is very small, forcing the speculum wide open will have the opposite effect: The placement of the cannulas, and finding them during the operation,3 will be more difficult (see Figs. 19.1 and 21.7).
–The speculum is able to prevent being closed by the squeezing patient.4
1Who typically spread the lids only loosely to avoid exerting pressure on the globe.
2This may be exacerbated by the wake patient squeezing.
3Especially of the superonasal cannula, which will tend to slide under the lid (see Fig. 19.1).
4This holds true for the duration of the entire operation.
© Springer International Publishing Switzerland 2016 |
173 |
F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,
DOI 10.1007/978-3-319-19479-0_19
174 |
19 The Speculum and Its Placement |
|
|
Fig. 19.1 Narrow palpebral fissure, widely opened speculum. It may be impossible to find the superonasal cannula when the surgeon wants to insert an instrument through it in the dark: a double-blind effort, according to the gallows type of humor. The cannula keeps sliding under the upper lid
–Wire-type speculums with no locking mechanism5 should be used only if the patient is under general anesthesia when squeezing of the lids does not occur. They work as a spring, whose action is easily overpowered by the orbicularis muscle.
•The speculum should have no conspicuously outcropping parts (see Fig. 19.2).6 This avoids getting sutures entangled by the speculum.7
•The speculum should not have long areas of contact8 (“solid blades”) with the lids (see Fig. 19.3). This avoids the danger of an intraocular instrument such as the probe, forceps, or scissors slipping on them and causing the intraocular tip to unexpectedly “jump” (especially during scleral indentation; see Sect. 28.2).
–Conversely, these speculums are able to keep the eyelashes securely out of the field.
5For example, the Barraquer Wire or the Kratz Wire.
6For example, Guyton Park, Liebermann, or Kratz Wing.
7Most microscopes have a relatively small field of view even at their lowest magnification. Either the microscope must be manually moved to identify what has caught the suture or the nurse may help – but she may not realize that as she is pulling on the thread of the suture to free it up, she is also pulling it out from the wound.
8For example, Sauer or Feaster.
19.1 General Considerations |
175 |
|
|
Fig. 19.2 The selftightening lid speculum. Speculums with outcroppings (arrows) whose only function is to snare sutures. See the text for more details
Fig. 19.3 A speculum with a long blade. The length of the blade presents a risk during scleral depression (see the text for more details)
176 |
19 The Speculum and Its Placement |
|
|
19.2Speculum Placement
•Upon insertion, make sure the blades do not slide between the plastic sheet and the lid.
–Once this happened, the eyelashes will peek out, and from then on it is very difficult if not impossible to keep them away from the operative field.
•Be careful not to dislodge the already-placed first blade while inserting the second blade.
•Open the speculum wide, but do it slowly. Even well-anesthetized patients can feel pain if the lids are spread too far and too fast.
–It is best to open the speculum to the maximum the lids allow and then loosen it a little.
•When securing the speculum width with a screw,9 make sure it is tight enough – but do not overtighten because you will have to struggle loosening it at the conclusion of the operation.
–Ideal is a self-tightening speculum that prevents the patient from squeezing the lid fissure smaller and has no unnecessary outcroppings (see Fig. 19.4).10
Fig. 19.4 The ideal self-tightening lid speculum. Not requiring a threaded tightening mechanism, this speculum reduces complexity and has no unnecessary outcroppings; it also has a wire type of “blade” that is sufficiently firm without being in the way. This is the speculum I favor
9For example, Cook or Clark.
10Geuder (Heidelberg, Germany) model G-16050.
Holding and Operating Hand |
20 |
Instruments |
As mentioned before (see Sect. 2.1), the fellow should carefully observe the way the surgeon’s hands and fingers manipulate the instruments he uses. What happens outside the eye explains some of what is happening inside, how external movements relate to internal consequences.
20.1Holding an Intraocular Instrument1
•Holding a device with two fingers is far from ideal under any circumstances.2 Intraocular tools (see Fig. 39.2) but especially intravitreal instruments need to be secured with three fingers (see Fig. 20.1a, b) to prevent any unintentional movement.3
•Using a forceps (see Fig. 20.1c and Sect. 13.2.1.3) to perform tasks requiring miniscule movements4 with a very small margin of error requires the greatest possible stability.
Pearl
There is a reason why chairs have (at least) three legs: they offer stability. Everybody would laugh at a chair with two legs. The same principle applies to holding intraocular tools.
1Most of what is discussed here is true for non-intraocular tools as well, but the margin of error is smallest when fine movements on the retinal surface are required.
2Next time your hair is cut, notice that the barber holds the scissors with three, even four, fingers.
3Support for the hand (wrist) is also essential (see Sect. 16.2.1).
4As a reminder, the ILM is 2 μ thick (see Sect. 5.11).
© Springer International Publishing Switzerland 2016 |
177 |
F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,
DOI 10.1007/978-3-319-19479-0_20
178 |
|
20 Holding and Operating Hand Instruments |
|
|
|
a |
b |
c |
Fig. 20.1 Holding the probe. (a) Supporting the probe with only the index finger and the thumb makes it rather unstable, which is risky if fine maneuvers, such as working in the proximity of the retina, are required. (b) By adding the middle finger, the position and movement of the probe are precisely controlled by the surgeon. (c) If a forceps is used, it is even more critical to provide adequate support. Since in this case the surgeon not only holds the tool but must actually squeeze it to enable its function, the use of the supporting middle finger is mandatory
One of the most common mistakes a beginner surgeon makes is to squeeze the tool even when the instrument is simply held, not actively used, or if the tool is a non-squeezable one (e.g., light pipe).5 This is a reflex, probably associated with the high concentration VR surgery demands. However, such squeezing not only offers no benefit, it is potentially detrimental since it increases the magnitude of tremor.
Pearl
The fellow must continually make a conscious effort to not squeeze the instruments unless squeezing is called for and even then to keep the force of squeezing to the minimum (see Sect. 4.1).
20.2Operating an Intraocular Instrument6
The intravitreally inserted tools are used to execute actions inside the eye but also to rotate the eyeball.7 Whenever an instrument is inserted into the vitreous cavity, there is potential for seesaw action with the fulcrum being at the sclera (see below).
5Call it “sympathetic squeezia.”
6More on this topic is provided in Chaps. 13 and 32.
7One of the disadvantages of having a single tool inside the eye during the slit-lamp approach (see Sect. 17.2) is the limited ability to maneuver the eyeball.
20.2 Operating an Intraocular Instrument |
179 |
|
|
•To rotate the eyeball the instruments in the two superior sclerotomies must move in harmony (see Sect. 25.2.8). As an example, if you want to turn the right eye toward 9 o’clock, you cannot tilt it by using your right hand only. Both tools must move to the right, equidistant and in exactly the same direction, and do so simultaneously.
–During rotation, there is no seesaw action: the external and internal parts of the tools move in the same direction (see Fig. 20.2).
•The seesaw comes into play when the surgeon needs to access a different area in the vitreous cavity without having to rotate the eye. As an example:
–While the posterior pole is in view, the field of action is to switch from the peripapillary area to one just temporal to the macula. The intraocular tools must be rotated (not the eyeball: the fulcrum remains stationary) so that their external and internal parts move in opposite directions (see Fig. 20.3).
Fig. 20.2 Rotating the eyeball. The external (thick arrow) and internal (thin arrow) parts of the intraocularly inserted tool move in the same direction; there is no seesaw action
Fig. 20.3 Switching the field of action inside the vitreous cavity. The external (thick arrow) and internal (thin arrow) parts of the intraocularly inserted tool move in the opposite directions; there is seesaw action with the fulcrum (blue circle) being at the scleral insertion point