Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6023_Библиотеки_им_академика_М_И_Перельмана.pdf
80
5 Basic Steps andTechniques ofVitrectomy
(4) Securing and Arranging the Perfusion Line
Use the surgical drape to secure the proximal end of the perfusion tube and arrange
the tube from the vitrectomy machine to the inner opening of the trocar. First, ensure
that the proximal perfusion tube has a gentle curve (Fig.5.6) to avoid excessive
kinking. This reduces friction, prevents sudden narrowing or blockage of the tube
lumen, and helps avoid insufcient or delayed entry of uidor gas into the vitreous
cavity, which could otherwise lead to ocular collapse, choroidal detachment, or even
expulsive choroidal hemorrhage.
(5) Inserting the Light Pipe Through the Upper Trocar
Beginners are particularly prone to errors during this step and must pay special
attention. The surgeon’s hand-eye-foot coordination may decrease due to mental
tension, mainly manifested in the following aspects:
1. The surgical eld suddenly shifts from the ocular surface to the intraocular
space, requiring corresponding adjustments to microscope focus and magnication. At this time, the surgeon must maintain hand stability and foot pedal
exibility.
2. The surgeon is highly nervous, leading to stiffness of the hand joints, which may
easily injure the lens. The surgeon should keep the hand joints naturally relaxed
while applying appropriate force to maintain a rm grip on the intraocular
instruments.
3. Due to inexperience or excessive tension, the depth of the light pipe entering the
vitreous cavity cannot be accurately estimated, which may lead to puncturing the
Fig. 5.6 Ideal curvature of
the proximal end of
perfusion line
5.2 Basic Steps
81
posterior pole retina, causing bleeding and retinal tears. If the macula is involved,
the patient’s visual recovery will be seriously affected. The surgeon should accurately determine the allowable intraocular length of the instrument by observing
the length of the outer end that has not yet entered the vitreous cavity.
After the light pipe safely enters the vitreous cavity and aligns with the surgical
wide-angle lens, the surgeon observes the intraocular light through the eyepiece.
The surgeon should rst maintain hand stability (avoiding large movements of the
light pipe) and then adjust the microscope foot pedal for focus. Once the optic disc
and retinal vessels are clearly visualized, the next step can proceed.
(6) Inserting the Cutter to Start Vitrectomy
Beginners should proceed to this step only after properly adjusting the microscope
and light pipe, as improper handling of the cutter tip may cause iatrogenic injuries.
“Never operate if you cannot see clearly”—this is one of the fundamental principles
of intraocular surgery. The cutter should rst be activated in the central vitreous
cavity. After removing part of the central vitreous, posterior vitreous detachment
(PVD) is induced. Creating PVD and accurately determining whether any vitreous
remains at the posterior pole are key skills that beginners need to master, and will be
elaborated on later.
(7) Removing Adequate Vitreous
Adjust the depth and angle of the light pipe to fully visualize the vitreous in different regions using the Tyndall phenomenon, and remove as much vitreous as possible with the cutter (Fig. 5.7). When shaving off peripheral vitreous or vitreous
around retinal breaks, where the vitreous cortex is denser and adheres more tightly
to the retina, use high-speed cutting (e.g., 5,000 cpm) with low vacuum(100–250
mmHg). The foot pedal can be tapped to achieve slow, controlled shaving. In
a
Fig. 5.7 Tyndall phenomenon. (a) Tyndall phenomenon in nature. (b) Inducing Tyndall phenom-
enon with a light pipe during vitreoretinal surgery
b
82
5 Basic Steps andTechniques ofVitrectomy
addition, iatrogenic lens injury must be strictly avoided. In phakic eyes, the surgeon
should always keep both hands coordinated and stay clear of the“unsafe zone” near
the posterior lens capsule.
(8) Other Intraocular Operations
After removing an adequate amount of vitreous, the surgeon may proceed with
other intraocular procedures, such as uid/airexchange, internal limiting membrane
peeling, and retinal laser photocoagulation. These techniques will be detailed in the
following chapters.
(9) 360° Scleral Indentation
The importance of scleral indentation is self-evident, but it also places high demands
on both thesurgeon and the assistant. Beginners should proceed step by step and
may rst familiarize themselves with the technique in pseudophakic eyes.
There are three main methods of scleral indentation:
1. The assistant holds a strabismus hook or scleral depressor, while the surgeon
holds a light pipe to illuminate the indented area. This is the most commonly
used method, offering a short learning curve and high safety.
2. One of the upper trocars is kept closed (if the trocar lacks a self-sealing valve, a
scleral plug is inserted). The surgeon holds the depressor and examines the
depressed vitreous and retina using external microscope illumination through
the pupil.
3. Under chandelier illumination, one upper trocar is also kept closed, and thesur-
geon holds the depressor to expose the peripheral retina.
Each of these three methods has its own advantages and disadvantages. The surgeon may choose based on the specic situation and personal preference. If an
assistant is unavailable or inexperienced, the latter two methods are good options
to learn.
(10) Removing the Upper Trocar
Regardless of whether vertical or oblique incisions are made, the surgeon must carefully inspect each incision. If leakage is detected and adequate tightness is not
achieved, suturing is required to reduce the risk of postoperative hypotony and
infectious endophthalmitis.
(11) Removing the Lower Trocar and Checking for Incision Leakage
If intraocular pressure is low, an appropriate amount of balanced salt solution or
ltered air can be injected 4mm posterior tothe superior limbus using a neneedle
to rapidly elevate the pressure. If the eyeis soft, the needle may easily injure the lens
during injection. In such cases, micro-toothed forceps can be used to grasp the conjunctiva around the injection site before inserting the needle.
The above mainly describes the conventional steps and precautions of PPV.The
surgeon may adjust according to personal preference, but must keep three key principles in mind throughout the procedure: (1) stable intraocular pressure; (2) a clear
5.3 Practical Skills andDetailed Illustration
83
surgical eld; and (3) appropriate instrument distance. Standard three-port PPV
accounts for an increasing proportion of vitreoretinal surgeries. Although the technology and instruments have matured, and their safety and efcacy have been
step learning approach, strictly follow the vitreoretinal surgery learning curve, and
ultimately master this skill with condence.
5.3 Practical Skills andDetailed Illustration
5.3.1 Creation ofScleral Incision
(1) Position and Direction of Scleral Incision
In standard three-port PPV, the trocar should be placed 4mm posterior to thelimbus
in phakic eyes and 3.0-3.5mm behind the limbus in aphakic or pseudophakic eyes.
This positioning ensures that the blade passes through the pars plana, which is avascular; therefore, bleeding does not occur from the incision. The pars plana adheres
tightly to the underlying choroid and will not detach due to sharp trauma. The ora
serrata, located approximately 1–2mm away, is also tightly adherent, further preventing subretinal uid from spreading to this area. The trocar placement must
always avoidiatrogenicdamage tothe long ciliary arteries and nerves.
For oblique incisions, it’s recommended thatthe direction of the incision be parallel to the tangential direction of the limbus (Fig.5.8).
widely recognized in long-term clinical practice, beginners must adopt a step-by-
(2) Sequence and Precautions for Trocar Placement
The lower trocar should be placed rst, typically in the inferotemporal quadrant. In
special cases, such as signicant choroidal detachment or a temporal silicone buckle,
the inferonasal quadrant may be chosen rst. The lower trocar should not be placed
too close to the eyelid margin. Taking the right eye as an example, it is generally
Fig. 5.8 Recommended
incision direction (at the
red dot); the blue line is the
tangential direction of the
limbus
84
5 Basic Steps andTechniques ofVitrectomy
positioned at the 7:30 to 8:00 o’clock position to avoid contact with the eyelid speculum, which could cause trocar slippage or interfere with scleral indentation.
In the following situations, special attention should be paid to ensuring prompt
connection of perfusion to the lower trocar:
1. Preoperative low intraocular pressure: After conrming that the inner opening of
the trocar has entered the vitreous cavity, perfusion should be turned on promptly
to maintain intraocular pressure.
2. Previous vitrectomy with intraocular uid or gas tamponade: After trocar place-
ment, if perfusion is not turned on promptly, a large amount of intraocular uid
or gas will escape from the eye, causing a sudden drop in intraocular pressure.
3. Elderly patients: Vitreous liquefaction is often signicant. If perfusion is not
turned on promptly, the liqueed vitreous will overow through the trocar, leading to a drop in intraocular pressure.
In the above situations, valved trocars may also be used to improve surgical safety.
The upper trocars are recommended to be placed at the 2:00 and 10:00 o’clock
positions (with a 120° angle between them) for the following three reasons:
1. Ergonomically, when both hands cooperate at this angle—similar to holding a
steering wheel—the wrist is in a naturally extended position, offering the greatest range of motion and optimal stability for intraocular movements (Fig.5.9).
2. The two upper trocars serve as stable fulcrums, allowing the surgeon to slightly
adjust eye position using intraocular instruments. If the angle is too small, the
range of motion is reduced; if too large, the eyeball is prone to horizontal rotation.
3. This conguration not only maximizes the reach of intraocular instruments
within the eye but also maximizes protection of the posterior lens capsule when
both hands are coordinated. If the angle is too large, the posterior lens capsule is
very likely to be touched during peripheral vitreous removal (Fig.5.10).
a b
Fig. 5.9 Wrist ergonomics. (a) Angle of holding the steering wheel. (b) The two upper trocars
maintain a 120° angle
5.3 Practical Skills andDetailed Illustration
Fig. 5.10 A
superotemporal trocar
placed too inferiorlywith
an excessively large angle
may cause the cutter to
injure the posterior lens
capsule when cutting the
superior vitreous; the
correct position is shown
by the green dot in the
gure
(3) Creation of Self-Sealing Sclerotomy
1. Advantages and Disadvantages of Non-Self-Sealing and Self-Sealing Incisions
If self-sealing is not a consideration, the incision perpendicular to the scleral
surface is the safest. This is because the trocar’s trajectory through the scleral
wall is the shortest, the inner end of the trocar extends farthest into the vitreous
cavity, and the elastic force from the scleral collagen bers is evenly distributed
around the trocar, making it less likely to slip during eye movements.
Although non-self-sealing incisions possess certain clinical merits, we recommend that beginners prioritize mastering the creation and management of
self-sealing (sutureless) scleral incisions. These techniques offer several distinct
advantages: (1) optimized operative efciency with shorter surgical times; (2)
enhanced patient comfort through a reduction in postoperative foreign body sensation; and (3) a minimized risk of suture-induced inammation and surgically
induced astigmatism.
2. Anatomical Principles of Self-Sealing Incisions
The creation of self-sealing scleral incisions is governed by two fundamental
principles: (1) The three-dimensional nature of tissue entry: An incision is not a
simple linear cut on a two-dimensional plane, but a dynamic tunnel through the
scleral architecture. Its length, depth, and angle must be synchronized to create
a valvular effect. (2) The utilization of spherical geometry: The eyeball is a
curved surface rather than a at plane. By accounting for this natural curvature
during trocar insertion, the surgeon can create a longer, tangential tunnel that
leverages intraocular pressure to facilitate a secure, self-sealing closure.
For example, in cataract phacoemulsication, we understand why the inci-
sion is not made perpendicular to the corneal surface but rather as a trapezoidal
incision. The reason is that this conguration provides good self-sealing and
effectively prevents postoperative wound leakage. By extension, the self-sealing
of a scleral incision is also closely and directly related to the trajectory of the
puncture knife through the ocular surface tissues.
85
86
ab
cd
5 Basic Steps andTechniques ofVitrectomy
3. Methods of Creating Self-Sealing Incisions
Conjunctival displacement must be performed rst, after which the scleral inci-
sion can be created using one of the following three methods (Fig. 5.11):
(a) Direct oblique insertionof the trocar-cannulainto the vitreous cavity.
(b) First, makevertical insertion into the sclera, andthen makeoblique insertion
into the vitreous cavity.
(c) Oblique insertionof the sclera to half depth, followed by oblique puncture
in the opposite direction into the vitreous cavity.
As shown in Fig.5.12, the third insertion method is the most stable because the
forces from four directions are balanced, and the wound will not shift.
Fig. 5.11 Schematic
diagrams of different
self-sealing scleral
incisions. (a) Oblique
incision; (b
oblique incision; and (c)
forward-reverse oblique
incision (V-shaped
incision)
) vertical-
a
b
c
Fig. 5.12 Creation of V-shaped incision. (a) First, perform conjunctival displacement, and then
insert the blade obliquely along the tangential direction of the limbus into the scleral lamella. (b)
After the tip enters the lamella, insert the blade obliquely in the opposite direction along the tangential direction of the limbus to the vitreous cavity. (c) The trocar has been inserted into the
scleral. (d) All trocars are removed after the surgery, and no obvious leakage is found
5.3 Practical Skills andDetailed Illustration
87
5.3.2 Safety ofthePerfusion Line
Maintaining astableperfusion pressure is essential for the safety ofvitreoretinal
surgery. Beginners must understand the specic causes of perfusion abnormalities
and quickly master their solutions.
After connecting the tip of the perfusion lineto the trocar, a small piece of drape
can be used to secure the perfusion lineto the zygomatic region, slightly outside and
below the trocar. At the same time, the proximal end of the perfusion lineshould
maintain a gentle curve, not too high or too low (see Fig. 5.6).
When the assistant indentsthe peripheral sclera, or when the surgeon moves the
patient’s eyeball, the inner opening of the perfusion cannula may sometimes tilt
upward and enter the anterior chamber through the angle or iris (Fig.5.13). This is
particularly concerning under high-pressure gas perfusion (e.g., 50 mmHg), where
the anterior chamber will deepen sharply, the surgical eld under the wide-angle
lens will become immediately blurred, and magnication will decrease accordingly.
This phenomenon should be identied and corrected promptly.
When the lower perfusion cannula becomes displaced from the scleral, the surgeon should promptly detect the following signs:
1. Soft eyeball: Due to the lack of continuous supplementation of perfusate or gas,
intraocular pressure will continue to drop to near atmospheric pressure, and the
outward pressure exerted by intraocular contents on the scleralwill decrease.
Treatment is relatively simple, justpromptly reconnect the infusion line or inject
uid into the vitreous cavity to maintain intraocular pressure and eliminate
the risk.
2. Localized choroidal elevation: Due to the sudden drop in intraocular pressure, if
not handled promptly, this may further lead to ocular collapse and even choroidal detachment (Fig.5.14). As long as intraocular pressure is promptly maintained, the choroidal detachment can also subside within a short time.
3. Explosive choroidal hemorrhage: If intraocular pressure remains low without
prompt treatment, choroidal detachment is likely to progress to extensive choroidal hemorrhage. At this stage, management becomes very difcult, and it may be
necessary to close the incision and perform a second-stage operation. When
Fig. 5.13 The inner
opening of the infusion
trocar pierces the iris and
enters the anterior
chamber, with gas lling
the entire anterior chamber
88
Fig. 5.14 Choroidal
detachment caused by
displacement
ofperfusion line
5 Basic Steps andTechniques ofVitrectomy
choroidal hemorrhage begins, the patient may sometimes complain of obvious
ocular distension and pain, followed by uncontrollable breath-holding and eyelid
closure, which will increase the difculty of the surgeon’s management.
If no obvious complications occur, the solution for perfusion cannula displacement is shown in Fig.5.15. The key factor is maintaining normal intraocular pressure throughout the procedure to avoid a cascade of adverse events caused by
hypotony.
Next, we list the causes and solutions of perfusion pressure abnormalities in the
following table (Table5.1).
5.3.3 Posterior Vitreous Detachment (PVD)
(1) Importance of Posterior Vitreous Detachment
Posterior vitreous detachment (PVD) refers to the loss of adhesion between the
posterior vitreous cortex and the internal limiting membrane. In the general popuMatchCaseReplacelation, the vitreous gradually liquees with age, manifested by
collapse and condensation of the collagen ber scaffold, degradation of hyaluronic
acid molecules, and gradual formation of internal cavities. The normal gel-like
structure of the vitreous progressively disappears, ultimately leading to PVD.During
preoperative fundus examination, the surgeon must carefully determine whether
PVD is already present in theeye. The most intuitive sign is the presence of a Weiss
ring (Fig.5.16).
ab
cd
5.3 Practical Skills andDetailed Illustration
Fig. 5.15 Treatment of perfusion line displacement. (a) Connect the perfusion tube to the upper
trocar to maintain intraocular pressure. (b) Insert a scleral plug into another trocar to ensure no
eyeball collapse during insertion of the trocar-cannula. (c) Re-insert the lower trocar, and at this
time, the intraocular pressure can be temporarily increased to maintain the hardness of the eye wall
for the ease of insertion. (d) Reconnect the perfusion line to the lower trocar
89
For example, in fresh rhegmatogenous retinal detachment, the presence of PVD
often indicates that the difculty of PPV is relatively low, and the surgeon may be
more inclined to choose PPV as the preferred treatment. The presence (or intraoperative creation) of PVD is a prerequisite for effective vitrectomy and an important
guarantee of long-term surgical success. Unless the Weiss ring is clearly visualized
during surgery, the surgeon must repeatedly conrm whether PVD has been successfully induced—this is particularly important in young patients (Fig. 5.17).
Beginners should always remember a fact: when you think you have removed
most of the vitreous quickly and well, the truth is often that most of the vitreous is
still adhering to the retina (Fig.5.18).
(2) Principles of Creating PVD
Beginners can adopt a step-by-step approach to inducing PVD intraoperatively, following these four principles:
1. First remove the central vitreous to disrupt the internal vitreous structure. The
inow of perfusate will further liquefy the posterior vitreous, creating favorable
conditions for subsequent PVD.
2. Begin inducing PVD above the optic disc. Use gentle negative pressure to aspi-
rate the vitreous (typically holding for 2–3 seconds before pulling the cutter
peripherally to allow the cutter port to better engage the posterior vitreous cortex). Then, follow the direction of the nerve ber layer into the four quadrants to
minimize transverse traction on the nerve ber layer.