Ординатура / Офтальмология / Английские материалы / Ocular Traumatology_Kuhn_2008
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472 Ferenc Kuhn
Summary
A chronically low IOP is incompatible with visual function, threatening even the normal size of the eye. Some of the pathologies that cause
hypotony are treatable, others result in inexorable damage. Early recognition and treatment are usually able to prevent phthisis.
References
[1]Bellows AR, Chylack LT Jr, Hutchinson BT (1981) Choroidal detachment. Clinical manifestation, therapy and mechanism of formation. Ophthalmology 88: 1107−1115
[2]Berkowitz RA, Klyce SD, Kaufman HE (1984) Aqueous hyposecretion after penetrating keratoplasty. Ophthalmic Surg 15: 323−324
[3]Delgado MF, Daniels S, Pascal S, Dickens CJ (2001) Hypotony maculopathy: improvement of visual acuity after 7 years. Am J Ophthalmol 132: 931−933
[4]Dohlman CH, D’Amico DJ (1999) Can an eye in phthisis be rehabilitated? A case of improved vision with 1-year follow-up. Arch Ophthalmol 117: 123−124
[5]Loewenstein A, McKinnon S, DiBernardo C (1997) Echographic diagnosis of scleral fold in hypotony. Am J Ophthalmol 124: 260−261
[6]Toris CB, Pederson JE (1987) Aqueous humor dynamics in experimental iridocyclitis. Invest Ophthalmol Vis Sci 28: 477−481
2.20 Endoscopy
Claude Boscher and Ferenc Kuhn
2.20.1Introduction
The very first use of an endoscope in ophthalmology was reported in 1934; the indication was ocular trauma [6]. Significant recent technological advances, such as reduced size, increased resolution, and probe resterilization and disposability, may make endoscopy a mainstream option in the diagnosis and treatment of eyes with a variety of diseases [3, 4, 7], including PVR [8] and injury [1, 2].
2.20.2Technical Overview
Figure 2.20.1 shows the assembled system. The quality and thus usefulness of the visual information available for the surgeon depend on several parameters:
•Number and quality of fibers dedicated to image transmission
•Focal distance of the handpiece’s lens(es)
•Distance of the handpiece from the target
•Angle of illumination
Autoclave.
While description of the equipment and its operational setup are not among the goals of this book, this brief exception is made here to facilitate understanding of the technology.
474 Claude Boscher and Ferenc Kuhn
Fig. 2.20.1 An assembled endoscopy system.1 The fiber optics transmission probe is connected to a three-chip CCD camera equipped with an ultrasensitive automatic shutter. The probe is fully autoclavable.2 Universal connections are used so that the probe can be connected to endoscopic cameras as well as light and laser sources already available in the OR. This more than offsets the original costs of the technology
1 OS Endoskopie, Jesi, Italy
2 As required by WHO rules. This is especially important in traumatology, where surgery can be time-consuming and with an increased risk of endophthalmitis.
•Magnification
•Resolution of the camera
•Size of the operative field and of the targeted image
•Attributes of the light source and the distribution of the light
•Size, quality, and settings of the video monitor
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2.20.3Advantages and Capabilities of Endoscope Use in Ocular Traumatology
The advantages and capabilities of endoscope use are as follows:
•With endoscopy, the timing of surgery is determined by the condition of the injured tissues, not by the clarity of the media. If visualization of the posterior segment is severely compromised by the corneal damage and vitrectomy is urgent, the surgeon may want to forgo using the TKP (see Chap. 2.15). Endoscopic bypassing of the anterior segment opacities [1, 3] spares the patient of the potential complications of performing PK on an acutely injured eye. If PK becomes necessary subsequently, it can be scheduled so that the risk of transplantation-related intraand postoperative complications is reduced.
•During EAV, progressive intraoperative opacification of the cornea or lens does not jeopardize surgical success.
•The endoscope helps identify the site for ideal sclerotomy placement, including that for the infusion cannula. The proper position of the cannula’s port can be confirmed before the infusion is opened.
•Endoscope use allows inspection of intraocular spaces that are impossible or very difficult to view by traditional methods: the posterior surface of the iris; the lens capsules, bag, and the IOL behind the iris; the zonules and capsulozonular complex; and the ciliary body.
•The endoscope makes it unnecessary to employ scleral indentation, regardless of whether it would be used to examine or treat the crucial peripheral structures . Foregoing scleral indentation means that pathologies, such as ciliary body detachment or vitreoretinal traction, are inspected “in vivo”, i.e., without physical distortion. The presence of anterior PVR or cyclitic membranes [2, 3] is not only easier to recognize, but their true effect on the normal tissues can be observed.
i.e., is it in front of, rather than underneath, the retina and uvea.
i.e., anterior retina, pars plana, ciliary body.
476 Claude Boscher and Ferenc Kuhn
Fig. 2.20.2 Endoscopic peeling of the anterior vitreous base. This eye had an IOFB injury, and the retina was also detached. Endoscopy-assisted vitrectomy was performed 20 days later. Blood, adherent to the pars plana, is being dissected and removed
•With proper technique, complete and unhindered intraoperative inspection is achieved, both circumferentially (360° visualization of all anterior structures; see Chap. 2.8) and antero-posteriorly (from the retrolental to the subretinal space). Endoscopy thus has unique significance in eyes whose injuries involve the posterior eye wall (see Chaps. 2.9, 2.14).
–The endoscope is not simply a diagnostic tool: with its high-mag- nification and high-resolution image and tangential approach it allows performing surgical tasks (e.g., EAV) that would be difficult or impossible to accomplish with traditional viewing techniques. An incomplete list of such tasks includes:
–Dissection of the vitreous base area to remove vitreous, blood (Fig. 2.20.2), proliferative cells, stem cell ingrowth [9], scar tissue, and cyclitic membranes [2, 3]
–Releasing traction to help reattach the retina, choroid, and ciliary body (Figs. 2.20.3, 2.20.4)
–Complete removal of the vitreous from behind the lens
i.e., using multiple sclerotomies in the presence of a clear lens.
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–Freeing the iris (see Chap. 2.6) from scar tissue grown over its posterior surface or “unrolling” of a retracted iris [8]
–Repositioning subluxated or luxated IOLs
Fig. 2.20.3 Endoscopy-assisted vitrectomy revision of the ciliary body area after failure of conventional vitrectomies. A thick cyclitic membrane is adherent to a corneal wound, and there is ciliary detachment. The iris and cornea are visible at the top of the image. The flow is raised up to 14 ml/m to allow grasping of the elastic membrane. Even though complete removal was not possible, the remnants could be dissected from the ciliary epithelium
Fig. 2.20.4 Endoscopy-assisted vitrectomy revision of complex posttraumatic anterior segment pathologies. Tangential, high-magnification view of the peeling of adhesions between the ciliary body and vitreous, which is also incarcerated into the corneal wound. The retracted iris and cornea are visible on the right side of the image
478 Claude Boscher and Ferenc Kuhn
2.20.4Disadvantages and Difficulties
of Endoscope Use in Ocular Traumatology
When switching from microscopic to endoscopic (video monitor) viewing, the learning curve is quite steep, due to the following:
•Difference in image composition. Instead of observing the inside of the eye and the intraocular instruments through the microscope’s eyepieces, the image is shown on the video monitor. This image corresponds to what is found in front of the endoscope’s tip inside the eye, and the endoscope itself is not visualized.
•Loss of stereopsis.
•Lack of visual feedback of the surgeon’s hand motions and the endoscope’s position.
ZPearl
Alternatively observing the video monitor or the microscope-provided image helps with orientation and probe manipulation by allowing identification of anatomical landmarks such as the lens or the optic disc. Switching the view is especially important for the less experienced surgeon.
•Different method of establishing position. Like in B-scan ultrasono graphy, the endoscope’s orientation determines the orientation of the image, e.g., simple rotation of the probe between the surgeon’s fingers changes what is up or down.
•Different method of moving along the operative field. This is done no more via directing the microscope along the x−y axis with a foot pedal but by moving the endoscope inside the eye.
Once the endoscope is introduced through the pars plana, the surgeon observes the inside of the eye and all intraocular maneuvers on the video monitor, not through the microscope.
It is as if the surgeon’s very eyes were placed inside the patient’s eye.
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•Different method of changing the magnification. Bringing the endoscope closer to the target makes the image larger, and vice versa.
•Inability to perform bimanual surgery.
•Difficulty in dealing with major fresh bleeding if it covers the endoscope’s tip.
ZCave
Endoscope use and especially EAV can be much more difficult in ocular traumatology than for other indications and are best left for the surgeon already experienced in endoscopic and trauma surgery.
2.20.5Issues Related to Surgical Technique
The initial step is to introduce the endoscope through a standard sclerotomy to determine the ideal sites for the infusion cannula, the working instruments, such as the vitrectomy probe, and, possibly, the endoscope itself.10
ZPearl
The initial sclerotomy for the endoscope should be at no more than 3 mm from the limbus. This reduces, although does not eliminate, the risk of iatrogenic retinal injury during endoscope introduction.
This is significant when tissues with high resistance, such as mature cyclitic membranes, are encountered; tearing of the underlying ocular tissues (e.g., ciliary epithelium, iris root) is a real risk. With advances in technology, bimanual surgery will likely become possible in the future, making these maneuvers easier and less risky.
Preoperative B-scan ultrasonography, the UBM, or transcleral illumination may help identify the most optimal site for the initial entry (see Chap. 2.16).
10 i.e., if it is found that the initial entry site is not ideal.
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•If the eye is hypotonous, intravitreal injection of BSS or air11 can restore the IOP and make endoscope insertion easier.12
Further difficulties13 and important issues include:
•Loss of visibility of the normal anatomical landmarks
•Detachment of the ciliary body, choroid, and/or retina
•Anterior displacement of the vitreous base/retina
•Massive fresh hemorrhage that interferes with or completely blocks visualization
•A long (6 or 7 mm) infusion cannula should be used; it must be sharp14 since choroidal, ciliary body, and retinal detachment, and thick, elastic cyclitic membranes adherent to the pars plana are not uncommon (Fig. 2.20.3). Self-retaining cannulas require special attention so they do not get expelled.15
•Loss of view intraoperatively. If blood covers the probe’s tip, the endoscope should be withdrawn and cleaned. This may have to be done repeatedly, if necessary.
•Number of sclerotomies. If the eye is phakic and the lens is to be preserved, a fourth sclerotomy may be needed to avoid lens injury. This is especially important if extensive manipulations at the vitreous base are required to prevent or treat an anterior PVR.16
•Core vitreous. This is the initial step of vitrectomy. The direction of vitreous removal is antero-posterior (see Chap. 2.9), and it usually starts in the visual axis. In a severely traumatized eye, even without a purulent infection, it may difficult, if not impossible, to distinguish between a
11This is a good advice for any eye with low IOP. The maneuver nevertheless requires experience so that the needle does not inflict further tissue damage and the fluid or air is not injected under the retina.
12If visibility allows, an AC maintainer can also be used.
13These are not necessarily specific to endoscopy.
14The track created with the MVR blade can rapidly close due to tissue elasticity.
15The risk is higher during EAV than in conventional vitrectomy because of the rotation of the eye during peeling at the vitreous base.
16Obviously, complete scar removal takes precedence of lens preservation (see Chap. 2.9).
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detached and necrotic retina and layers of vitreous tainted with streaks of blood and coated with fibrin (see Chaps. 2.12, 2.17). Preoperative ultrasonography may have been unfeasible, or yielded erroneous (see Fig. 1.9.5) or undecipherable information. With its high magnification, the endoscope has a good chance of allowing recognition of the retina17 before it is penetrated.
•Posterior cortical vitreous. Its detachment and removal is crucially important and represents the second step of vitrectomy. Separation may be aided by PFCL use. The endoscope-provided control increases safety and efficacy. The surgeon should also be familiar with the type, parameters, and settings of his vitrectomy machine. To avoid undue traction on the retina, a machine with flow control18 is preferred; when working in close proximity to the retina, the flow should be low (1−2 ml/m) and the cutting speed set at below 15 cpm or even “cut by cut.”
•Peripheral vitreous. The last phase of vitrectomy is to remove as much of the vitreous, hemorrhage, fibrin, membranes, or scar tissue in the periphery as possible. Avulsion of the anterior vitreous base or ciliary detachment is not uncommon: the endoscopic hyaloido-capsulo- zonulo-ciliary dissection must therefore be performed cautiously to avoid injuring the zonular system or the ciliary epithelium. One of the surgeon’s hands holds the endoscope that doubles as a light pipe while the other hand operates the usual vitrectomy instruments. A complete, 360° job can be accomplished by utilizing all sclerotomies and repeated switching of the hands as needed. The endoscope also allows complete cleansing of the sclerotomies, assuring that no tissue remains or gets incarcerated. The vitrectomy machine’s settings may have to be similar to those described above. Helpful additional tricks include the following:
–Blood, accumulated between various tissues, can be used as a marker to help delineating boundaries and cleavage plans, thus facilitating dissection.
17Nevertheless, this may remain a challenge even for the experienced surgeon.
18i.e., using a peristaltic, not Venturi, pump.