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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6023_Библиотеки_им_академика_М_И_Перельмана.pdf
7.3 Fundamental Steps andKey Precautions
141
For laser closure of retinal breaks, two methods are generally employed: (1) The
spot array method, in which laser spots are arranged in an orderly pattern around the
break, spaced 0.5–1 spot diameter apart, and typically consisting of 3–5 consecutive
rows (Fig.7.3); and (2) The continuous method, in which laser spots are interconnected to form a linear chain that encircles the entire break, generally requiring only
two rows. Beginners should strive for neatly placed laser spots, though absolute
perfection is not required; this is akin to handwriting, where whether one uses regular script or cursive, the result is acceptable as long as the placement is accurate and
the intention is clear.
Since hemoglobin absorbs laser energy, laser can also serve a hemostatic function. After uid/air exchange, if a small amount of bleeding occurs at the break
edge, laser photocoagulation can be used to achieve rapid hemostasis without
electrocautery.
The time for a laser spot to mature is generally 5 days (which explains why PPV
with ltered air tamponade has a high success rate for retinal detachment with superior breaks). As the laser spots mature, their diameters expand to approximately 1.5
times their original size.
(3) Laser Parameter Settings
Laser parameters for retinal photocoagulation primarily involve three adjustable
settings: (1) Laser power, where starting at 100 mW is appropriate, with subsequent
titration based on the clinical appearance of the laser spots; (2) Duration, with a
standard range of 150–200 ms being appropriate; and (3) Interval, with 150–200 ms
being appropriate. Beginners may benet from setting a longer interval to allow
Fig. 7.3 Laser
photocoagulation to
sealretinal breaks
142
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7 Surgical Intervention ofRhegmatogenous Retinal Detachment: Part 2 (Pars Plana…
Fig. 7.4 Fundus of a patient with ocular albinism, in which the effect of retinal laser photocoagulation is often poor. (a) Retinal detachment with xed folds in the left eye; no breaks were found.
(b) Fundus photograph of the right eye
sufcient time for intraoperative reection and judgment, thereby minimizing the
risk of accidental tissue injury—particularly to the macula—caused by surgical
anxiety.
The closure of retinal breaks relies primarily on the absorption of laser energy by
melanin in the RPE layer. In cases of chronic retinal detachment with tissue edema,
laser energy and duration may need to be appropriately increased to produce reliable laser spots. Additionally, in individuals with lighter RPE pigmentation—such
as Caucasians and patients with ocular albinism (Fig.7.4)—laser energy should
also be increased accordingly.
7.3.8 Intraocular TamponadeAgents
Select the most suitable intraocular tamponade agents based on the location and size
of the retinal breaks, as well as the severity of retinal detachment. Beginners often
tend to use silicone oil, which is understandable. However, given the higher incidence of silicone oil-related complications and the need for secondary removal, the
use of silicone oil should be gradually reduced. Filtered air also has a denite effect
on superior breaks, but it is not particularly recommended for beginners because its
volume dissipates quickly.
7.4 Details ofAir/Fluid Exchange
143
7.3.9 Adjusting Intraocular Pressure
. After injecting an intraocular tamponade agent, IOP must be carefully monitored,
as uctuations are common—for instance, hypertension is frequently associated
with silicone oil, while hypotony is often seen with gas tamponade. IOP can be
assessed using two practical methods: (1) Observing optic nerve head perfusion
using a light guide ber to ensure adequate vascular ow; and (2) Gently palpating
the sclera with the pulp of the index nger to gauge rmness. If uncertain, the surgeon may palpate the patient’s nose or forehead through the surgical drape for comparison; a scleral rmness similar to that of the nasal tip typically suggests a normal
IOP range.
7.3.10 Closing Scleral Incisions andAdvising thePatient
toMaintain aFace-Down Position
To determine whether there is leakage from the scleral incisions, beginners are
advised not to overlook the importance of suturing, even for self-sealing incisions.
Suture if necessary; sutures can be removed one week postoperatively. In addition,
it is important to check for incarceration of uveal tissue or vitreous at the incision
sites. A cutter may be used to remove tissue exposed outside the incision. When
suturing scleral incisions, the depth of needle insertion must be strictly controlled to
avoid full-thickness penetration of the eyewall; otherwise, bacteria may be introduced into the vitreous cavity during postoperative suture removal, potentially causing infection.
Finally, if silicone oil or gas tamponade is used, the patient and their family
should be instructed to maintain a face-down position postoperatively. Although
some studies suggest that strict face-down positioning may not be necessary for
detachments caused by superior breaks, the face-down position remains the most
universal and easiest for patients to follow. For highly compliant patients, however,
they can be individually instructed.
7.4 Details ofAir/Fluid Exchange
7.4.1 Advantages andDisadvantages
The most direct benet of air/uid exchange to drain off subretinal uidis that it
maximally reduces the use of heavy liquid, which facilitates laser photocoagulation
or cryotherapycryopexy. Additionally after air/uid, the peripheral retina can be
directly visualized withoutscleral indentation. However, in cases where clarity is
poor, scleral indentation should be combined to achieve a thorough 360° inspection
and treatment of peripheral abnormalities.
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7 Surgical Intervention ofRhegmatogenous Retinal Detachment: Part 2 (Pars Plana…
7.4.2 Key Points andDifficulties
For beginners, air/uid exchange generally does not present great difculty. The key
points are adequate exposure of the breaks and proper use of the ute needle. The
main difculties include the following two aspects.
1. Decreased clarity of the surgical eld. Due to the mixture of uid and air, the
refractive interface within the vitreous cavity is temporarily disrupted.
However, as the proportion of gas increases, the blurring will resolve in a short
time. This process is similar to an airplane passing through clouds during takeoff and landing (Fig.7.5). As long as surgical norms are strictly followed, the
procedure is relatively safe, and the surgeon need not be overly nervous. For
beginners, it is not recommended to aspirate subretinal uid directly with a
cutter, as this may accidentally engage the edge of the break, potentially
enlarging the retinal break (Fig.7.6). This is especially concerning when the
break is located at the posterior pole, where such accidental aspiration may
involve the macula and result in irreversible visual impairment.
2. Unskilled drainage technique. Either active drainage with a cutter or passive
drainage with a ute needle may be used. However, due to the negative pressure
at the instrument tip and the decreased clarity of the surgical eld after air/uid
exchange, certain complications are more likely to occur, primarily including:
(1) the tip easily aspirating the edge of the break, causing enlargement of the
break; (2) the tip contacting the underlying RPE and choroid, leading to bleeding
(Fig.7.7); and (3) failure to adjust the eye position adequately to drain sufcient
subretinal uid.
a b
Fig. 7.5 Air/uid exchange can temporarily reduce fundus visibility. (a) The entry of air bubbles
reduces visibility in the vitreous cavity. (b) Schematic diagram of an airplane passing through clouds
7.4 Details ofAir/Fluid Exchange
145
a
b
c
Fig. 7.6 Drainage of subretinal uid with a cutter during air/uid exchange. (a) Using a cutter to
drain subretinal uid from the primary break. (b) The retina at the posterior edge of the primary
break is accidentally aspirated by the cutter. (c) The range of the retinal break is signicantly
enlarged
7.4.3 Application ofFlute Needle
(1) Passive Aspiration
When using a ute needle to drain subretinal uid via passive aspiration, the following two physical principles are primarily involved.
1. Siphon effect. When gas perfusion is turned on, the gas in the vitreous cavity
exerts continuous downward pressure on the retina and the underlying uid. At
this time, the pressure at the inner opening of the ute needle (from the subretinal uid) is higher than the atmospheric pressure at its outer opening. This pressure difference drives the uid upward along the tube and out of the eye.
146
7 Surgical Intervention ofRhegmatogenous Retinal Detachment: Part 2 (Pars Plana…
a
b
c
Fig. 7.7 Bleeding caused by the tip of the ute needle touching blood vessels when draining
subretinal uid
2. Capillary effect. This refers to the phenomenon in which liquid ows into a nar-
row tube or small gap without external force, driven by the adhesion between the
liquid and the object, as well as the surface tension generated by cohesion among
liquid molecules. This effect allows liquid to rise against gravity. When the tip of
the ute needle contacts subretinal uid, capillary action draws a small amount
of uid into the needle. Once this initial contact is established, the siphon effect
(pressure gradient) takes over to evacuate the uid from the eye.
7.4 Details of Air/Fluid Exchange
147
Therefore, when using a ute needle to drain subretinal uid through a relatively peripheral break, in order to ensure unobstructed and thorough drainage—in
addition to using a sufciently high gas perfusion pressure (usually 30–50
mmHg)—the tip should be kept within the uid at all times (but not too deep, to
avoid injuring the RPE layer), and the surgeon should strive to drain sufcient uid
“in one go.”
(2) Active Aspiration
In addition to using a cutter, a ute needle can also be used for active aspiration of
subretinal uid. The proximal vacuum connector of the cutter can be unscrewed,
and the ute needle can be connected to the vacuum.This method is efcient, but
care must be taken to avoid accidental aspiration of the retina, which may enlarge
the break.
7.4.4 Cooperation ofPatient’s Head Position andEye Position
One of the great advantages of using a wide-angle lens in PPV is that, during
air/uid exchange, sufcient subretinal uid can be drained by adjusting the
patient’s head and eye position without the need for heavy liquid tamponade.
This is also an important reason for the signicant reduction in the use of
heavy liquid.
How to better adjust the patient’s head position to assist subretinal uid drainage
can be accomplished through the following steps.
1. Determine the position of the break. If there are multiple breaks, select the reti-
nal break closest to the posterior pole for drainage.
2. Adjust head position. Based on the position of the break to be drained, ask the
patient to move their head toward the break’s clock-hour position (or gently
assist them).For example, if the break is located at the 6 o’clock position, ask the
patient to tuck their chin or adjust the eye position downward using the upper
two trocars as fulcrums (Fig.7.8).
3. Adjust eye position. Using the upper two trocars as fulcrums, hold the lightber
and ute needle with each hand and gently push the eyeball toward the break’s
clock-hour position. This furtherhelps drainage of thesubretinal uid.
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7 Surgical Intervention ofRhegmatogenous Retinal Detachment: Part 2 (Pars Plana…
Fig. 7.8 The retinal break
is located at the 6 o’clock
position. The head and eye
are directed downward
(green arrow) to bring the
break to the
lowestposition, thereby
facilitating adequate
aspiration of subretinal
uid
7.5 Systematic Approach toPrevent Inadvertent Perfusion
inEyes withExtensive Choroidal Detachment,
Suprachoroidal Fluid, andHypotony During Pars
Plana Vitrectomy
Approximately 10% of RRDcasesare complicated by extensive choroidal detachment. High-risk factors include older age, high myopia, long axial length, aphakia,
pseudophakia, and low intraocular pressure. In these cases, surgical difculty
increases signicantly, presenting an inevitable challenge for junior surgeons.
RRD with choroidal detachment is generally accompanied by suprachoroidal
effusion and hypotony (Fig.7.9). Anatomically, suprachoroidal effusion makes trocar insertion difcult. At the same time, hypotony renders the ocular wall soft, leading to difculty positioning the inner opening of the trocar within the vitreous
cavity. Moreover, when the inner opening of the trocar is surrounded by uveal tissue, uid or gas infusion into the vitreous cavity becomes even more challenging
(Fig.7.10).
When dealing with these challenges, we must address three mutually reinforcing
unfavorable factors: (1) Choroidal detachment; (2) Suprachoroidal effusion; and (3)
Hypotony. These three factors are intricately interrelated and often form a vicious
cycle. All appropriate surgical maneuvers must be centered on breaking this cycle,
as the key to resolving these issues lies in the effective restoration and maintenance
of stable intraocular pressure.
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7.5 Systematic Approach toPrevent Inadvertent Perfusion inEyes withExtensive…
Fig. 7.9 Choroidal detachment and suprachoroidal effusion. (a) Wide-eld fundus photography
shows retinal detachment and choroidal detachment. (b) UBM shows suprachoroidal effusion
(white asterisk) and ciliary epithelial detachment (white arrow)
149
Fig. 7.10 The inner opening of the trocar is surrounded by the uveal tissue. (a) When inserting the
trocar, the inner opening of the trocar is partially surrounded by the dark brown uveal tissue (white
arrow). (b) The inner opening of the trocar is completely surrounded by the uvea (white arrow)
How can intraocular pressure be improved and maintained? The author
(Zhang)has developed a step-by-step surgical approach that has been proven to be
safe and efcient.It does not require additional scleral incisions for drainage of
suprachoroidal effusion (please refer to the website for detailed demonstration:https://link.springer.com/article/10.1007/s12325-018-0801-2). This approach
is briey presented here for reference (Fig.7.11).
150
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7 Surgical Intervention ofRhegmatogenous Retinal Detachment: Part 2 (Pars Plana…
e f
Fig. 7.11 Step-by-step surgical management of choroidal detachment complicated with suprachoroidal effusion (a) Measure the point 4mm behind the limbus. (b) Injecting balanced salt solution 4 mm behind the limbus (transconjunctival intravitreal injection) to increase IOP. (c)
Orange-yellow suprachoroidal uid is observed overowing passively into the subconjunctival
space through the injection site. After inserting the inferotemporal trocar-cannula, a ne needle is
used to continue injecting uid into the vitreous cavity. (d) Inserting an endoillumination light pipe
into the inferotemporal region to inspect whether the inner opening of the infusion cannula has
been successfully created and to observe any surrounding condensed intraocular tissues. (e) The
assistant uses curved forceps to create a centripetal indentation of the inferotemporal infusion cannula. (f) With endoillumination, using a vitrectomy probe to carefully peel off the uveal tissue
covering the inner opening of the infusion cannula and to remove the peripheral dense vitreous.
After conrming that the inner opening of the infusion cannula has completely entered the vitreous
cavity, the uid infusion is turned on