Part IV
VR Surgery: General Strategies and Tactics
Introduction
This part deals with general strategies and tactics in VR surgery. The operation is typically performed via the “standard” method (full-function vitrectomy machine, operating microscope, BIOM), but there are alternatives: the slit lamp, the endoscope, even a portable machine, the IBO, and 3D viewing. Each approach has its own advantages and disadvantages. Other chapters in this part discuss issues related to the general preparation of the patient, the placement of the sclerotomies/ cannulas, the illumination system, the relevant anatomical and physiological attributes of VR surgery, and, finally, clinical guidelines. These latter chapters go through the most commonly employed maneuvers such as vitreous removal from the anterior and posterior segments, scleral indentation, lasering, working with preand subretinal membranes, the use of tamponades and dyes, and the handling of the lens as well as intraoperative complications.
Vitrectomy Performed via |
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the “Standard” Method and Its |
Alternatives1
17.1The “Standard” Approach: Microscope2 and BIOM
This is how the vast majority of surgeons perform the vast majority of their vitrectomies:
•Three ports (sclerotomies) are used.3
–A fourth, or even fifth, one may be used for additional (“chandelier”) lightning.
•The two, superior “working sclerotomies” are for the light pipe (typically in the surgeon’s nondominant hand) and for a working instrument4 (typically in the dominant hand).
–The tools are switched between the hands if required by the actual situation.5
•A third sclerotomy is created, usually inferotemporally,6 for the infusion cannula.
•Intraocular access is provided transconjunctivally,7 via cannulas that are introduced at the beginning and removed at the end of surgery (see Chap. 21).
•The surgeon views the entire surgery by looking into the eyepiece of the microscope.
–Almost all of the procedure in the posterior segment is done using the BIOM or a planoconcave contact lens.8
1The selection of the type of vitrectomy method is one of the decisions that belong to the second level of strategic planning (see Sect. 3.1).
2The microscope is typically in the coaxial position.
3There are variations on the number of ports used; for instance, the infusion, even in a phakic eye, may be placed in the AC, and thus only two, superior, sclerotomies are made.
4Probe, scissors, forceps, pics etc.
5For example, peripheral vitrectomy in the phakic eye.
6Occasionally the infusion cannula is switched into a superior position and the inferotemporal port is used for a working instrument (see Sect. 21.6.3).
7The previous “standard” was a 20 g vitrectomy with a separate conjunctival opening and dissection, followed by the preparation of sclerotomies with an MVR blade; no cannula (other than the infusion cannula) is placed inside the sclerotomy incisions (see Sects. 4.4 and 21.9).
8Except when working just behind the lens (see Sect. 27.5.3.) or in the periphery using indentation (see Sect. 28.3).
© Springer International Publishing Switzerland 2016 |
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F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,
DOI 10.1007/978-3-319-19479-0_17
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17 Vitrectomy Performed via the “Standard” Method and Its Alternatives |
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17.2The Slit-Lamp Approach
The microscope can be equipped with a slit illuminator, bringing the benefits, and some of the disadvantages, of the optical slit. The slit light makes the microscope act like a biomicroscope.
•Two ports are needed: one for the infusion and one for the working instrument; there is a single working instrument inside the eye.
–If the situation requires it, a third port can be added for a second working instrument.
•The illumination angle is ~6°.
•The surgeon views the entire surgery by looking into the eyepiece of the microscope.
–Most of the procedure is viewed through a three-mirror lens.
–Fine perimacular manipulations are viewed using a planoconcave contact lens.
–A “hybrid” approach is also possible, combining a wide-angle-viewing corneal contact lens with the slit lamp: it provides for a larger field.9
The advantages and disadvantages of the slit lamp/microscope are listed in
Table 17.1.
Table 17.1 The advantages and disadvantages of the slit lamp/microscope
Advantages |
Disadvantages |
Illumination as an optic cut allows |
The field of view is very small compared to |
visualizing details that would remain |
wide-angle viewing. The surgeon has excellent |
invisible or barely visible with |
resolution at the actual worksite (which is |
traditional lighting, for example: |
illuminated), but no feedback about what is |
Glass IOFB in the cornea |
happening elsewhere. For example, the far end |
Posterior capsule/anterior hyaloid face |
of a subretinal membrane can tear the retina as |
Fine details of the structure of the |
it is being pulled, but the surgeon’s visual field |
vitreous and the VR interface |
is limited to the area immediately surrounding |
Cellophane maculopathy |
the retinotomya |
Bimanual surgery is readily available if a |
The light reflex from the corneal contact lens is |
third sclerotomy is prepared |
bothersome |
If only one working instrument is inside |
If only a single working instrument is inside the |
the eye, the surgeon’s nondominant |
eye,c it is much more difficult to stabilize the |
hand is free to do other tasks: |
globe; this is especially a risk if the patient is |
Scleral indentation |
under local anesthesia and the akinesia is not |
Adjusting the contact lens’ position |
absolutely perfect |
Stabilizing the working instrumentb |
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(see Fig. 2.1) |
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Reduced risk of phototoxicity |
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aAkin to a person with advanced glaucomatous damage or retinitis pigmentosa. At the bus stop he can discern the number of the arriving bus, but the recognition that a bus is arriving is partly deduced from nonvisual sources (noise, memory, fellow would-be-passengers’ change in behavior etc.) bWith the nondominant hand’s fingers.
cA fulcrum is present at the sclerotomy site.
9 Although it is still not as large as with the standard approach.
17.4 Portable Systems |
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17.3The Endoscope Approach (EAV)
With all alternative approaches, the image is captured outside the patient’s eye, irrespective of whether the illumination is internal or external.10 The endoscope’s image capture is inside the vitreous cavity; the illumination is transmitted via the same endoscope probe, acting as a light pipe.
Typically, the endoscope probe is held in the surgeon’s nondominant hand, freeing the dominant hand for handling the traditional tools of PPV. Endoscopy for VR surgery may be employed as a purely diagnostic tool,11 as a therapeutic method,12 or as supplementary weapon.13
One of the major differences between all other approaches and endoscopy concerns the use of scleral indentation. In many conditions it is crucially important to visualize the periphery and remove the vitreous, membranes, fibrin etc. With alternate approaches this can be achieved only if scleral indentation is employed (see Chap. 28). Endoscopy eliminates the need for indentation since the surgeon places “his own eyeballs” into the eye and can view otherwise invisible areas without distorting the anatomy.
EAV has many benefits and a few tangible downsides (see Table 17.2).
Pearl
Endoscopy also proves one of the dogmas in VR surgery wrong: it is possible for a surgeon lacking binocular vision to perform it. Those who have never had binocular vision will be able to learn vitrectomy without difficulty; those who used to have but lost it will need to relearn much of it and reenter the field only gradually – but they should not be prevented to do so solely based on having monocular vision.
17.4Portable Systems
There are smaller,14 portable devices15 that can be used in the office.16 These are intended not for full PPV but limited purposes such as sample-taking, removing vitreous blood, core PPV etc.
10See Sects. 17.1 and 17.2, respectively.
11For example, evaluating the condition of the ciliary processes.
12To perform most or all of the operation via endoscopic viewing (EAV).
13Performing PPV via the traditional (or slit lamp) approach and utilizing the endoscope for certain, limited functions such as checking the vitreous base.
14Otherwise, the trend in the industry is to manufacture large, heavy (exceeding 50 kg), difficult- to-transport vitrectomy machines.
15May even be battery-operated.
16Where the legal system permits this. In many countries, even intraocular injections must be given in the OR, not in the office.
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17 Vitrectomy Performed via the “Standard” Method and Its Alternatives |
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Table 17.2 The advantages and disadvantages of endoscopy |
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Advantages |
Disadvantages |
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Both the illumination and the image |
A rather steep learning curve,b which is due to the |
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capture are inside the eye; the quality |
following inherent characteristics: |
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of the view is excellent irrespective of |
The VR image is viewed on a monitor, not |
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any media opacity or pupil sizea |
through the microscope |
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2D, not 3D, imagingc |
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The endoscope probe itself remains invisible on |
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the monitor |
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The orientation is difficult since “up” and |
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“down” are not fixedd |
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True bimanual surgery is impossible since one |
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hand of the surgeon is dedicated to holding |
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the endoscopy probe the entire timee |
The resolution of the image is very highf |
The view may be blocked if the endoscopy probe is |
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submerged in blood; it needs to be removed and |
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cleaned |
The visual field and magnification can be |
Risk of phototoxicity when working in close |
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easily changed by the surgeon via |
proximity to the retina |
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positioning the endoscope tip closer |
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tog, or further away fromh, the target |
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area |
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Any and all areas of the vitreous cavity |
The resolution of the smaller-gauge (i.e., 23) |
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(vitreous base, ciliary body, posterior |
endoscopy probe may not be sufficient to allow |
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iris surface etc.) are accessible for |
fine workj |
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both diagnostic and therapeutic |
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purposes and without the need for |
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scleral indentationi |
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The illumination is coaxial; there is no |
The probek itself is invisible; there is a risk of lens |
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shadowing |
damage if the surgeon tries to “reach over” to |
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the other side in a phakic eye |
The placement location (and introduction) |
There is an inaccessible zone behind the tip of the |
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of the infusion cannula and of the |
endoscopy probe |
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working sclerotomy can be properly |
Expense of the equipmentl |
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selected and visually controlled once |
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the endoscopy probe has been inserted |
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into the eye |
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aObviously, leftover opacities anterior to the vitreous cavity will represent a problem in the postoperative period; this is something the surgeon must keep in mind as he is planning his surgical strategy. bHow steep, of course, depends on the individual surgeon. Paradoxically, those with less experience using the standard approach may have less difficulty switching than those who have been operating via the microscope/BIOM approach for long.
cThe surgeon will develop pseudostereopsis with time.
dThe field of view is not changed by adjusting the position of the microscope (as with the standard or slit-lamp approaches) and rotating the eye but by repositioning the endoscope.
eThe laser channel can be incorporated into the endoscopy probe (single sclerotomy needed for endocyclophotocoagulation or even panretinal laser treatment).
fEquipment-dependent, but technology is advancing fast. gSmaller field, higher zoom.
hEnlarged field, lower zoom.
iWhich distorts the anatomy: it can hide the presence of VR traction by approximating its endpoints (see Chap. 28).
jLess important at the vitreous base than in the posterior pole. kAgain, it also acts as the light pipe.
lThe cost is expected to decrease as the EAV grows in popularity.