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4 Preoperative Preparation andAnesthesia
4.3.1 Local Anesthesia
(I) Commonly Used Methods
Common anesthesia methods used in vitreoretinal surgery include retrobulbar anesthesia, peribulbar anesthesia, and sub-Tenon block. As retrobulbar anesthesia
remains the most commonly used local anesthesia method in China, we will focus
on its injection technique and precautions here.
(II) Retrobulbar Anesthesia
Retrobulbar anesthesia involves injecting anesthetic drugs into the intraconal space
(the posterior muscle cone) to block the ophthalmic branches of cranial nerves III,
IV, V, and VI; to immobilize the eyeball; and to eliminate sensation in the conjunctiva, cornea, and uvea, while also reducing extraocular muscle tension.
1. Injection method. Generallyin China, a retrobulbar injection needle with a total
length of 38mm and a diameter of about 0.4mm is used. The needle is initially
inserted vertically at the junction of the lateral and middle thirds of the inferior
orbital rim. The needle tip’s bevel and the barrel’s markings should be aligned
and face the globe. Once the needle reaches a depth of 20 mm—passing the
equator of the eyeball (noting that highly myopic eyes have a longer axial
length)—or when the tip gently contacts the orbital oor, the needle is redirected
approximately 30° superiorly and nasally. As the needle reaches a total depth of
30–35mm (measured from the skin surface), the tip should be positioned within
the muscle cone, between the optic nerve and the lateral rectus muscle. Before
injection, aspiration is mandatory to conrm the absence of blood reux. Upon
conrmation, 3–4 mL of anesthetic is injected. The total insertion depth must not
exceed 35 mm, and excessive nasal angulation must be avoided to prevent injury
to the optic nerve or major orbital vasculature (Fig.4.3).
2. Retrobulbar anesthesia in high myopia.Given the high prevalence of high myo-
pia in East Asia, surgeons must account for the characteristic elongated axial
length and the potential presence of posterior staphyloma in these patients.
During retrobulbar injection, in addition to following standard protocols, it is
crucial to avoid premature redirection of the needle. Upon entering the muscle
cone, the angulation should be more acute (atter) than usual; excessive nasal or
superior tilting increases the risk of globe perforation at the site of the staphyloma. Such an injury often involves the macula, leading to devastating and irreversible visual loss (Fig.4.4).
3. Choice of anesthetic drugs. Two percent lidocaine is commonly used for retro-
bulbar anesthesia. It can also be mixed with 0.75% bupivacaine in a 1:1 ratio to
prolong intraoperative analgesia or relieve postoperative pain. The mixture must
be thoroughly blended before injection. The onset time of lidocaine is 4–6 minutes, and its duration of action is 40–60 minutes. The onset time of bupivacaine
is 5–11 minutes, and its duration of action is 4–12 hours. For non-complex vitreoretinal surgeries, most of which can be completed within one hour, lidocaine
ab
cd
ef
4.3 Choice ofAnesthesia
71
Fig. 4.3 Retrobulbar anesthesia. (a) Insert the needle at the junction of the outer and middle thirds
of the lower orbital margin. (b) Insert the needle vertically. (c) After inserting the needle vertically
for approximately 20 mm, change the direction of the needle to tilt 30° upward and nasally. (d)
After the total length of the needle entering the orbit reaches 30–35 mm, aspirate the syringe to
conrm no blood reux. (e) Hold the syringe rmly with the left hand and inject the anesthetic
with the right hand. (f) Side view of retrobulbar injection
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4 Preoperative Preparation andAnesthesia
ab
Fig. 4.4 High myopia with posterior staphyloma: retrobulbar injection carries a risk of macular
injury. (a) Side view (b) Posterior-pole view
can be used alone. If intraoperative analgesia is insufcient, a small additional
dose of anesthetic can be administered.
4. Eye compression. After injecting the anesthetic, use gauze to apply pressure to
the eyeball for 5–10 minutes, releasing pressure every 10–15 seconds, to promote diffusion of the anesthetic, reduce intraocular pressure, and minimize retrobulbar bleeding. Oculopression is particularly necessary in the following
situations:
(a) For patients with a low pain threshold and emotional tension, oculopression
can reduce the anxiety caused by sudden pain when cutting the conjunctiva
or depressing the sclera.
(b) For patients undergoing macular surgery, oculopression can promote full
diffusion of the anesthetics, more effectively immobilize the eyeball, and
reduce operative errors caused by the patient’s eye movements.
(c) For patients with hypertension or diabetes, oculopression not only reduces
the probability of retrobulbar bleeding but also provides timely compression
and hemostasis when a small amount of bleeding just occurs, thereby avoiding the impact of excessive orbital pressure on the blood perfusion of the
eyeball.
5. Treatment of complications. If the eyeball gradually protrudes, orbital pressure
is excessively elevated, eyelid closure becomes difcult, or upper eyelid ptosis
occurs, the operation should be stopped immediately. The eyeball should then be
bandaged with pressure, and surgery should be rescheduled (usually after 2–3
days). If bleeding is minimal with no obvious proptosis or persistent elevation of
orbital pressure, the operation may be continued. For patients with diabetes or
hypertension that may compromise intraocular blood perfusion, scleral incision
4.3 Choice ofAnesthesia
73
or anterior chamber paracentesis should be performed promptly, and vitrectomy
may be used to remove part of the vitreous or release aqueous humor to lower
intraocular pressure and restore normal intraocular blood perfusion as soon as
possible.
6. Cooperation during surgery. During local anesthesia, the patient may experience
the most noticeable pain during the following steps: (1)lifting the rectus muscle
(during scleral buckling, if this step causes the patient signicant pain, the patient
must be calmed before subsequent scleral external uid injection; gentle language and movements are essential to help avoid choroidal hemorrhage);
(2)scleral indentation (especially when depressing the nasal sclera); (3)subconjunctival injection; and (4)removal of the surgical patch.
Patients with good vision can observe the movement of surgical instruments
abovethe retina. When performing delicate macular operations, patients should be
informed and comforted in advance to alleviate their nervousness and avoid sudden
eye rotation while grasping the epiretinal membrane or internal limiting membrane,
which could damage the neuroepithelial layer and cause holes or bleeding.
Based on our experience, after the surgeon uses intraocular forceps to remove
part of the epiretinal membrane or internal limiting membrane, he or she can gently
shake the tissue within the vitreous cavity a few times and tell the patient that these
white membranes are the lesions that have been successfully removed. This positive
interaction can greatly improve patient compliance, allowing subsequent delicate
maneuvers to be performed more effectively (Fig.4.5).
ab
Fig. 4.5 Interaction during epiretinal membrane surgery. (a) Gently shaking the removed epireti-
nal membrane within the eye. (b) The patient describing the scene he or she sees at that moment
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4 Preoperative Preparation andAnesthesia
4.3.2 General Anesthesia
Compared with local anesthesia, general anesthesia is more expensive and requires
the cooperation of anesthesiologists and nurses, but its advantages are very
signicant.
The following patients can consider general anesthesia.
1. Young or mentally immature.
2. Easily nervous and agitated, with poor cooperation.
3. Sensitive to pain and require prolonged muscle traction or external scleral pres-
sure during surgery.
4. Have undergone multiple recent eye surgeries and are more sensitive to pain due
to tissue edema and inammation.
5. The surgery is expected to take a long time and be more complicated.
6. Suffering from claustrophobia.
7. With communication difculties.
It should be noted that for patients who may undergo uid/air exchange during
vitreoretinal surgery or who still have residual gas in the eye, nitrous oxide (N₂O)
should be avoided as a general anesthetic; otherwise, intraocular pressure in the
operated eye may rise sharply, potentially leading to irreversible visual impairment.
4.4 Summary
“By failing to prepare, you are preparing to fail.”In the realm of vitreoretinal surgery, where the threshold for error is near zero, meticulous preoperative planning is
not merely a preference but a prerequisite for success. Given the intricate nature of
intraocular maneuvers and the irreversible consequences of technical lapses, surgical preparation must extend far beyond the operating table.
A truly comprehensive plan begins with transparent and empathetic communication
with patients and their families, ensuring that expectations are managed and
informed consent is deeply understood. Furthermore, seamless collaboration within
the surgical team is vital; this involves synchronizing with attending physicians,
anesthesia staff, and nursing teams to anticipate every possible intraoperative
requirement.
Beyond interpersonal coordination, strict adherence to medical regulations and
standardized safety protocols serves as the nal safeguard. By fortifying every link
in this preparatory chain—from clinical assessment to logistical readiness—the surgeon can navigate the complexities of the posterior segment with condence, ensuring the smooth execution of the procedure and the highest standard of patient safety.
Basic Steps andTechniques
ofVitrectomy
Vitreoretinal surgery refers to a series of procedures that alter the pathological state
of the vitreous and retina to achieve anatomical reattachment and functional repair,
including various surgical methods and their combinations. The patient’s condition
and the surgeon’s experience jointly determine the most suitable combination of
approaches. Pars plana vitrectomy (PPV) is the most complex and important component of vitreoretinal surgery, with signicant individual variability. In this chapter, we will focus on PPV to introduce the basic steps and precautions of vitreoretinal
surgery.
5.1 Common Terms andInstruments
5
5.1.1 Instrument Diameter
In vitreoretinal surgery, gauge (G) is commonly used to indicate the diameter of
instruments. Although it is not a standard international unit of measurement, it
remains widely used in medicine—for example, to indicate the caliber of syringe
needles. This unit originated from the British wire industry. At a time when no universal thickness standard existed, gauge was conventionally used for thickness measurement and commercial transactions. There is no xed linear conversion between
gauge size and metric units. The corresponding relationship between the diameters
of commonly used vitrectomy instruments and millimeters (mm) is shown in
Fig.5.1.
5.1.2 Trocar-Cannula System
The trocar-cannula system is a fundamental instrument in vitreoretinal surgery. Its
function is to use a puncture knife to penetrate the scleral wall and retain the cannula
in place, serving as a channel for uid, gas, and instruments to enter and exit the
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2026
Z. Zhang, U. Spandau, Vitreoretinal Surgery,
https://doi.org/10.1007/978-3-032-25271-5_5
75
76
Fig. 5.1 Correspondence between vitreoretinal instrument gauges and millimeters (mm)
Fig. 5.2 The trocar-
cannula system: “trocar”
refers to the cannula at its
tip (indigo and purple
parts). (Photo courtesy of
Alcon)
5 Basic Steps andTechniques ofVitrectomy
vitreous cavity (Fig. 5.2). The word “trocar” (also spelled “trochar” in British
English) comes from the French “trocart,” which has been in use since 1694. It is
composed of two elements: “trois,” meaning three, and “carré,” meaning sides or
faces, referring to the instruments three-sided shape.
5.2 Basic Steps
In vitreoretinal surgery, for convenience of expression, “trocar” is often used to
refer to the cannula retained in the scleral wall. This convention is also adopted in
this book.
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5.1.3 Vitrectomy Machine
The vitrectomy machine mainly provides cutting power and an illumination source
for ophthalmic surgery. There are various brands and series available, which have
undergone multiple upgrades. Existing vitrectomy machines have greater stability
and more complete functions, and can support multiple intraocular operations
simultaneously, such as retinal laser photocoagulation, intraocular electrocoagulation, and cataract phacoemulsication. Most vitrectomy machines employ venturi
pumps, which must be connected to high-pressure gas to provide power. The most
prominent advantage of using a venturi pump is that the on-off state of the negative
pressure at the cutter opening can be exibly and immediately controlled by the
surgeon, avoiding accidental injury to intraocular tissues due to machine delay.
5.2 Basic Steps
First, it is necessary to ensure that the patient has a good and stable head position,
and that the periorbital skin is routinely disinfected. To better prevent infection,
topical anesthetics and 5% povidone-iodine can be instilled into the conjunctival sac
in sequence and left in place for at least one minute. According to domestic and
international research reports, as well as our years of experience, this method can
effectively prevent the occurrence of infectious endophthalmitis.
5.2.1 Selection ofPPV
Before deciding to perform PPV, the surgeon should objectively evaluate the risks
and benets and carefully consider the following three questions:
1. What vitreoretinal disorder does the patient expect to address?
2. What other treatment methods are available besides PPV to solve this problem?
3. Can you handle or, with prompt help from others, resolve the difculties and
possible complications during the surgery?
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5 Basic Steps andTechniques ofVitrectomy
5.2.2 Basic Objectives ofPPV
1. Ensure unobstructed entry of uid and gas into the vitreous cavity.
2. Facilitate subsequent intraocular operations.
3. Avoid iatrogenic injuries, especially protecting the retina and lens.
4. Achieve good wound closure and rapid healing.
5.2.3 Basic Operation ofPPV
(1) Surgical Draping and Eyelid Speculum Placement
The purpose is to enclose the upper and lower eyelashes within the drape, secure the
surgical eld, and avoid contamination caused by overow of the perfusate. Special
attention must be paid to sealing the nasal orbital margin and nasal root to prevent
water vapor exhaled by the patient from condensing on the surgical contact lens and
compromising the clarity of the surgical eld (Fig. 5.3).
(2) Creating Transconjunctival Scleral Incision
For 23G and 25G vitrectomy, scleral incisions may be created either vertically or
sealing and architecturally sound. Achieving a high-quality incision becomes signicantly more challenging in the following scenarios: (1) profound hypotony (low
intraocular pressure); (2) pediatric patients due to increased scleral elasticity; (3)
coexisting choroidal detachment or suprachoroidal effusion; and (4) re-operation
(previous vitrectomy) where the vitreous cavity is uid-lled. In cases of severe
hypotony, intraocular pressure should be restored prior to incision to prevent globe
collapse; this can be achieved by injecting balanced salt solution (BSS) into the
vitreous cavity via a 30-gauge needle, 3.5–4.0mm posterior to the limbus.
For PPV beginners, it is especially important to maintain a relaxed, natural wrist
position with the wrist slightly extended to ensure the puncture knife always
advances centripetally (Fig. 5.4). Excessive tension during trocar insertion may
obliquely, depending on the surgeon’s preference, provided the wound remains self-
Fig. 5.3 Standard surgical
draping
5.2 Basic Steps
Fig. 5.4 Correct wristangle for trocar insertion
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Fig. 5.5 Incorrect wristangle for trocar insertion
cause involuntary wrist stiffness and overextension, potentially leading to lens
injury from the puncture tip (Fig. 5.5).
(3) Connecting the Perfusion Line to the Lower Trocar
First, conrm that the inner opening of the trocar has fully entered the vitreous cavity. When intraocular pressure is low (≤9 mmHg) or the retina is highly detached,
before turning on the perfusate, it is essential to verify complete entry of the trocar’s
inner opening. The simplest method is to gently push the outer opening of the trocar
slightly upward toward the center of the vitreous cavity (taking care to avoid contact
between the inner opening and the posterior lens capsule). If the inner opening is
visible through the pupil, perfusion can be turned on. Alternatively, using a surgical
wide-angle lens and a light pipe inserted through the trocar opposite the perfusion
trocar, if the metal reection of the inner opening is clearly visible, perfusion can be
turned on. We will elaborate on how to eliminate risk factors and ensure safe entry
of the perfusion cannula into the vitreous cavity in the presence of choroidal detachment with low intraocular pressure in the following chapters.