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ab
3 Intraocular TamponadeAgents
(4) Silicone Oil Dislocation
Because silicone oil is a uid, it can migrate outside the vitreous cavity during or
after surgery. Due to its high viscosity and surface tension, it rarely ows back on
its own. Dislocation may occur in the following locations:
1. Anterior chamber High-risk patients: (1) high myopia; (2) aphakia; (3) zonular
laxity; (4) pseudophakia; (5) poor postoperative face-down positioning.
(a) Prevention during surgery: For aphakic or pseudophakic eyes, an inferior
peripheral iridotomy (Ando’s iridotomy) can be created (Fig.3.18a, b).
For heavy silicone oil, peripheral iridotomies should be placed superiorly. Illustrative case: A patient with an unremarkable right eye underwent
vitrectomy with silicone oil tamponade and was instructed to maintain facedown positioning. That night, the left eye developed severe distending pain,
which subsided spontaneously during the hospital visit. Medical history
revealed that the left eye had undergone vitrectomy with lens extraction,
heavy silicone oil tamponade, and a superior peripheral iridotomy 10 years
earlier; the oil had never been removed and showed no signicant emulsication. UBM revealed complete angle closure and anterior chamber attening (Fig. 3.19a–c). The diagnosis was pupillary block caused by heavy
silicone oil entering the anterior chamber due to sustained face-down positioning. After discontinuing face-down positioning, the pain resolved and
did not recur.
Ando’s iridotomy was rst proposed by Fumitaka Ando (Nagoya Medical
University, Japan) in 1985. (He also invented the scleral nail for xing retinal aps, a valuable technique before the advent of heavy liquids.) In a correspondence published in Am J Ophthalmol, Ando rst suggested that a
circumferential incision at the iris base reduces silicone oil migration into
Fig. 3.18 Mechanism of action of Ando iridotomy. (a) Pupillary block caused by silicone oil. (b)
Ando iridotomy (inferior peripheral iridotomy) creates an alternate pathway for aqueous humor,
bypassing the pupillary block and preventing silicone oil migration into the anterior chamber
3.4 Silicone Oil
49
a
b
c
Fig. 3.19 An interesting case with concomitant tamponade of heavy and light silicone oils in each
eye. (a) No abnormality in the anterior segment of the right eye. (b) The left eye shows an open
superior iridotomy and a at anterior chamber. (c) UBM examination reveals complete angle closure and pupillary block
the anterior chamber. The formal results were published in Br J Ophthalmol
in 1987. Among 62 aphakic eyes with Ando’s iridotomy, only four (6.5%)
developed anterior chamber silicone oil dislocation after 7 months of
follow-up.
When performing Ando’s iridotomy with a vitrectomy cutter, maintain
intraocular pressure to prevent iris bleeding. Spontaneous closure occurs in
approximately 20% of cases, most commonly in younger patients and those
with multiple prior surgeries. The main cause is postoperative inammation
leading to brin exudation at the iridotomy. Combined postoperative miosis
and anti-inammatory therapymay act to maintain thepatency. If closure
occurs, laser iridotomy under slit lamp or surgical revision may be performed; however, this may aggravate iris inammation and often leads to
re-closure. Close follow-up is required.
50
3 Intraocular TamponadeAgents
(b) Postoperative treatment: For phakic and pseudophakic eyes, if silicone oil
overows into the anterior chamber and causes acute intraocular pressure
elevation, the anterior chamber can be ushed in the operating room. The
surgical pearlsare as follows: (1) If the anterior chamber becomes signicantly shallower, it indicates the presence of malignant glaucoma. Before
ushing the silicone oil in the anterior chamber, a trocar should be inserted
to release the excessive pressure in the vitreous cavity; otherwise, silicone
oil will continue to ow into the anterior chamber. (2) Use miosis to
increase the blockage of the lens-iris septum against silicone oil in the vitreous cavity. (3) Corneal incisions can be made at the 6:00 and 12:00 positions. Inject viscoelastic into the lower incision, squeeze the silicone oil
droplet toward the edge of the upper incision, and then gently press the
posterior lip of the upper incision to release the silicone oil droplets. (4)
Rinse the viscoelastic from the anterior chamber. Because uid can easily
ow back into the vitreous cavity, attention should be paid to releasing the
pressure in the vitreous cavity at this time. If necessary, some silicone oil
should be removed. (5) Finally, ltered air can be injected into the anterior
chamber. The surface tension of the gas prevents silicone oil from overowing again; on the other hand, it helps check whether the viscoelastic in
the anterior chamber has been sufciently removed.
2. Subretinal space: Subretinal silicone oil dislocation is rare but carries serious
consequences and greater treatment difculty. During oil injection, sudden globe
collapse can fold the trocar opening. If a large peripheral tear is present, especially with anterior PVR, oil may enter the subretinal space. Sometimes, the
managementrequires a large peripheral retinotomy to drive out the high-viscosity
oil droplets.
Postoperative subretinal oil dislocation occurs in recurrent retinal detachment
with signicant PVR, due to traction from broproliferative membranes that
enlarge new or existing tears. Prognosis is poor. Prevention focuses on the rst
surgery: ensuring complete posterior vitreous detachment and adequate vitreous
resection.
3. Suprachoroidal space: Suprachoroidal dislocation is extremely rare.It occurs
when trocar dislocation or choroidal bulge causes the trocar opening to lie in the
suprachoroidal space during oil injection. If it occurs, rst remove the trocar and
enlarge the scleral incision. Then, use silicone oil buoyancy and a cotton swab to
express the suprachoroidal oil through the scleral incision. This process is very
-time consuming, and IOP should be maintained stable throughout. To prevent
this rare accident, inject silicone oil under direct visualization with a
-wide angle lens.
(5) Toxicity to the Retina and Optic Nerve
Although the overall safety of silicone oil has been widely recognized, a small number
of silicone oil toxicity cases still occur. Clinically, it presents as severe postoperative
visual acuity loss and central scotoma. Morphologically, it often manifests as retinal
ganglion cell apoptosis and optic nerve atrophy. Unfortunately, no effective
3.4 Silicone Oil
51
prevention or treatment currently exists. Studies have shown that the retina is more
susceptible to phototoxic damage when the eye is lled with silicone oil; therefore,
excessively strong light should be avoided during silicone oil injection and removal.
In addition, other contributing factors should be excluded, such as accidental retrobulbar anesthesia and excessive intraoperative intraocular pressure.
(6) Silicone Oil Removal
Silicone oil removal can be performed via an anterior or posterior approach, both of
which are relatively straightforward. The anterior approach involves creating a capsulotomy in the posterior capsule after lens removal and expressing the silicone oil
through a corneal incision; intraocular lens implantation may be considered depending on the clinical situation. The posterior approach uses negative pressure from a
vitrectomy machine or a standard syringe to actively aspirate silicone oil through a
scleral incision.
In China, we often use themachine-independent method to remove the silicone
oil. The following is a brief description of its steps and precautions (Fig.3.20a–d).
a
c
Fig. 3.20 Machine-independent method to have silicone oil removal. (a) Insert the polyethylene
tube into the tip of a 10-mL syringe. (b) Use scissors to cut until 2~3mm is exposed. (c) Pay attention to keep the cross-section smooth and at. (d) Put the polyethylene tube on the trocar, retract
the syringeplunger, and drain off the silicone oil
b
d
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3 Intraocular TamponadeAgents
The approach is demonstrated below:
1. Prepare the silicone oil removal equipment. Insert a prepared polyethylene tube
into a 10-mL syringe, leaving approximately 2–3mm exposed. Cut the tube so
that the cross-section is smooth and at to ensure airtightness and avoid conjunctival trauma.
2. Insert the trocars. Insert the upper and lower trocars as usual. Use the temporal
trocar for uid infusion and the upper trocar for silicone oil removal.
3. Start uid perfusion. To prevent low intraocular pressure and silicone oil droplets from blocking the inner opening of the trocar, temporarily increase perfusion
pressure to 35–40 mmHg, then adjust to 20–25 mmHg after IOP stabilizes.
4. Aspirate silicone oil. Place the syringe (with the pre-covered polyethylene tube)
perpendicular to the scleral surface and buckle it onto the outer opening of the
trocar. Pull the syringe plunger by hand to generate negative pressure. A vascular
clamp may be used to kept the plungerin postion.
5. Continue to aspirate. When the oil-uid interface is observed through the pupil,
ne-tune the position of the upper scleral incision toward the apex of the eyeball
to ensure smooth silicone oil extraction and reduce sudden IOP changes.
6. Remove residual silicone oil droplets. The following methods can be used to
further ensure the complete removal of silicone oil: (1) Insert a ute needle to
guide the oil droplets. (2) Segmentally withdraw the upper trocar to allow uid
ow to ush out oil droplets hiding at its inner opening. (3) Use a squint hook to
depress the peripheral sclera. (4) Perform air/uid exchange.
7. Fully examine the fundus. Conrm complete silicone oil removal and check
whether additional treatment (e.g., further photocoagulation) is needed.
When using this method, we should pay attention to the following three points:
1. Avoid damaging the conjunctiva: The polyethylene tube is relatively hard and
may compress the conjunctiva. Excessive force can cause conjunctival injury.
Ensure the tube cross-section is smooth and at (trim with scissors if needed).
Do not apply excessive pressure to the conjunctival surface; only enough to
achieve adequate sealing.
2. Keep the syringe airtight: After the polyethylene tube is buckled onto the conjunctiva with appropriate pressure, pulling the syringe plunger generates negative
pressure. This negative pressure aspirates silicone oil while also drawing the conjunctiva tightly against the tube cross-section, creating a closed space that ensures
sufcient suction.
3. Pay attention to intraocular pressure uctuations. The syringe can generate negative pressure up to 650 mmHg, which is higher than machine-generated negative
pressure (Fig.3.21). When the trocar inner opening is blocked by silicone oil but
infusion is unobstructed, IOP uctuation is generally minimal. However, during
the nal stage of oil extraction, aspiration should be performed slowly. If IOP
becomes too low, release the contact between the syringe and the conjunctiva
promptly.
3.5 Heavy Liquid
53
Fig. 3.21
the 10-mL syringe is
pulled up to the 10 mL
mark, and the measured
negative pressure is
667.3 mmHg
The plunger of
Finally, it must be noted that because silicone oil is hydrophobic and highly viscous, it can be “ushed” out of the vitreous cavity by perfusion uid but cannot be
“washed” clean. After most of the silicone oil is removed, a small amount remains
adherent to the inner wall of the eyeball. Currently, no surfactant exists to help
remove this residual oil more thoroughly. Therefore, regardless of the removal
method used, some patients still complain of oaterspostoperatively—these are
caused by emulsied silicone oil droplets remaining in the vitreous cavity. This
phenomenon is more common in highly myopic eyes and young patients. In a small
number of patients, emulsied oil droplets may block the chamber angle and cause
elevatedIOP.
3.5 Heavy Liquid
3.5.1 Physical andChemical Properties
The chemical name of heavy liquid is peruorocarbon liquid (PFCL), a synthetic
uoride. The types commonly used in vitreoretinal surgery include peruoro-octane
(PFO), peruoroperhydrophenanthrene (Vitreon), peruorodecalin (PFD), peruorotributylamide (PFTB), and peruorooctylbromide (PFOB). PFD is the most commonly used type in China.
Heavy liquid is widely used in the chemical industry and has been gradually
applied in clinical practice since the 1960s. Due to its strong oxygen-carrying
capacity, it has been used as a blood substitute to save critically ill patients. Since
54
3 Intraocular TamponadeAgents
the 1980s, heavy liquid has played an increasingly important role in vitreoretinal
surgery, greatly reducing surgical difculty and signicantly improving success
rates. It is known as the “third hand” of retina surgeons.
The characteristics of heavy liquid related to vitreoretinal surgery include the
following:
1. High density: Approximately twice that of water. Since retinal density is roughly
equal to water, gravity can atten the retina, displace subretinal uid, and facilitate removal of dropped lens fragments.
2. Colorless and transparent: Ensures a clear surgical eld.
3. Low viscosity: Allows smooth injection onto the posterior pole and rapid removal
from the eye.
4. Chemical inertness: Does not react with other intraocular substances in the short
term, ensuring safety.
5. Refractive index: Close to water (1.33) but not identical, creating a refractive
interface that allows the surgeon to distinguish the heavy liquid level in the
vitreous cavity.
6. Vapor pressure: The vapor pressure indicates the ability of the molecules in the
liquid to leave the liquid and vaporize or evaporate. The higher the vapor pressure, the easier it is for the liquid to vaporize (the vaporization of the intraocular
uid will cause turbidity of the posterior capsule of the lens); at 37°C, the vapor
pressure of the heavy liquid peruorodecalin (PFD) we commonly use is
12.5mmHg, while the vapor pressure of water is 47.1mmHg, which means that
heavy liquid is not easy to vaporize in the eye, which can further ensure the clarity of the surgical eld.
7. Surface tension: Slightly lower than silicone oil, making it prone to form sh-
egg-like droplets in the eye. This is a major disadvantage, as droplets can easily
migrate through retinal breaks into the subretinal space. Therefore, droplet formation should be minimized during injection.
8. Interfacial tension: High interfacial tension between heavy liquid and water pro-
entering the subretinal space.
9. Incompatibility: Under normal use, heavy liquid does not mix with water, silicone oil, blood, or other intraocular substances.
motes a large, stable interface, which helps prevent intraocular uid from re-
3.5.2 Indications andUsage ofHeavy Liquid
With the popularization of wide-angle surgical lenses, the use of heavy liquid has
declined signicantly in recent years, especially in patients with fresh rhegmatogenous retinal detachment. As mentioned above, among the 61 patients with fresh
rhegmatogenous retinal detachment who underwent PPV, only one patient required
heavy liquid to reposition the retina (because the primary break spanned 5 clock
hours). In the remaining patients, the wide-angle lens assisted with head positioning, and most subretinal uid was drained through gas/liquid exchange. The small
3.5 Heavy Liquid
55
amount of residual subretinal uid was completely absorbed by the rst postoperative day.
Although the use of heavy liquid has declined signicantly, it remains a powerful
tool in certain vitreoretinal surgeries. Beginners should clearly understand its indications and strive to avoid complications during use.
3.5.3 Indications andEffects ofHeavy Liquid
(1) Giant Retinal Tear
Because giant retinal tear(GRT) occurs mostly at the periphery, surgical treatment
was very difcult before the advent of heavy liquid. The main problem was that the
posterior edge of the tear was prone to slippage and curling during uid/air exchange.
Gas entering the vitreous cavity diffuses from the periphery to the posterior pole,
generating a pressure difference that may cause the posterior edge of the tear to slip
and curl.
Various improved surgical methods were used, such as an inversion bed, prone
positioning, gas injection with retinal attening from posterior pole to periphery followed by supine repositioning, and transscleral retinal nails to prevent edge slippage.
Although these methods had certain advantages at the time, they were relatively difcult to perform. Understanding these challenges makes it easy to appreciate the
important role of heavy liquid in GRT surgery.
Heavy liquid has revolutionized GRT treatment, and its advantages are clearly
demonstrated during surgery: First, it xes the retina at the posterior pole, improving
the convenience and safety of delicate peripheral manipulations. Second, it can be
gradually advanced from the posterior pole to the periphery, xing the posterior edge
and corners of the retinal tear against the RPE layer, thereby creating stable conditions for laser photocoagulation. This effect is known as the “steamroller effect”
(Fig.3.22a–c).
(2) Proliferative Vitreoretinopathy (PVR)
There are two major problems in the surgical treatment of PVR: rst, a brous proliferative membrane at the posterior pole, which may present as a wide or narrow
funnel; second, intraretinal PVR, characterized by a hardened retinal texture, poor
mobility, and obvious shrinkage.
The role of heavy liquid in PVR surgery is reected in the following aspects:
1. Expanding the posterior pole retina. After complete peeling of the brous prolif-
shrinkage” state due to poor mobility—i.e., although traction is relieved, the
retina still cannot be adequately stretched. At this point, heavy liquid injection
and its “steamroller effect” help atten the posterior pole retina.
erative membrane at the posterior pole, the retina often remains in a “pseudo-
56
bc
3 Intraocular TamponadeAgents
a
Fig. 3.22 The “steamroller” effect of heavy liquid. (a) Working principle of the steamroller. (b)
After removal of the proliferative membrane at the posterior pole, retinal wrinkles remain. (c)
After heavy liquid injection, the retinal wrinkles at the posterior pole are attened
2. Reduce mobility of the peripheral retina. When the posterior pole is xed with
heavy liquid, the mobilityof the peripheral retina will be signicantly reduced,
which will help the surgeon to use a vitrectomy cutter to remove the dense
peripheral vitreous, and also provide a relatively stable force plane for the peeling of the proliferative membrane and bands.
(3) Retinal Detachment Without Macula Involvement or Secondary to
Peripheral Tears
For retinal detachment without macular involvement, a small amount of heavy
liquid may be injected onto the posterior pole before starting peripheral vitrectomy to prevent subretinal uid from spreading under the macula. However, the
injected volume should not be too large; it is best to keep the heavy liquid within
3.5 Heavy Liquid
57
the vascular arcades. Otherwise, heavy liquid may easily enter the subretinal
space and leave residual droplets postoperatively.
If the retinal tear is located in the periphery, draining subretinal uid using simple uid/air exchange is difcult. Heavy liquid can be injected onto the posterior
pole, up to just below the posterior edge of the tear. This displaces most of the subretinal uid from the posterior pole through the tear into the vitreous cavity. The
remaining subretinal uid in the periphery is then aspirated using uid/air exchange.
This technique is known as the “sandwich technique” (Fig.3.23a, b).
The obvious advantage of this method is that it prevents the surgeon from
creating a retinal break to drain subretinal uid and allows testing of the mobility
-and compliance of the mid peripheral retina during surgery. If the peripheral
retina remains incompletely at after gas/liquid exchange, heavy liquid should
not be injected in large quantities to try to “atten” the retina. The following
three problems must rst be ruled out: (1) Whether the peripheral vitreous has
been sufciently removed. (2) Whether there are proliferative membranes or
bands beneath or anterior to the retina. (3) Whether there is obvious retinal rigidity or shortening.
Heavy liquidmay also be employed in the following scenarios: (1) Complex retinal abnormalities resulting from trauma, such as retinal incarceration or subretinal
hemorrhage. (2) Dislocation of thelens or intraocular lens (though its use has been
declining). (3) Subretinal or suprachoroidal hemorrhage secondary to various
etiologies.
ab
Fig. 3.23 “Sandwich technique” for retinal repositioning. (a) Surgical video screenshot. The red
-dotted line indicates the gas water interface (subretinal uid and perfusion uid), and the blue dot-
-ted line indicates the water heavy liquid interface. (b) Schematic diagram of the technique