1. Vitreous substitutes are used in vitreoretinal surgery to provide tamponade during retinal detachment repair. 2. Conventional substitutes include gases (air, SF6, C3F8), liquids (saline, perfluorocarbons, silicone oil), while newer substitutes include semi-fluorinated alkanes and silicone oil/semi-fluorinated alkane combinations. 3. Each substitute has unique properties like surface tension, buoyancy and viscosity that contribute to retinal apposition and attachment. Complications vary between substitutes.

1. VITREOUS
SUBSTITUTES

2. DEFINATION
• These are substances used as adjuncts
to vitreoretinal surgery in complicated
forms of retinal detachment requiring
vitrectomy .
• They provide a long-term tamponade to
maintain the neural retina in apposition
to retinal pigment epithelium

3. CLASSIFICATTION
1. Conventional Vitreous substitutes
- Gases : Air, SF6, C3F8
- Liquids : Balanced salt solution, Perflourocarbon liquids and Silicone oil.
2. Newer Vitreous substitutes
- Semi Flourinated Alkanes
- Silicone Oil/ Semi Flourinated Alkanes combinations

4. PROPERTIES
VITREOUS SUBSTITUTE
Good tamponade High surface tension Sufficient buoyancy
inert
biodegradable
transparent
stable refractive index shock absorbing

5. 1. AIR :
• It was the first vitreous substitute employed intra
operatively by Ohm in1917
• They are not commonly used for internal tamponade as
it has no expansile property .
• Effect lasts for 3 days .
• Uses:
a) during scleral buckle surgery to restore intraocular
volume
b) to unroll the posterior flap of large retinal tears
c) fluid-air exchange can be helpful to improve visualization
of the retina in profuse intra-operative bleed .
The air bubble compartmentalizes the blood and also
may have HEMOSTATIC ACTION
CONVENTIONAL : INTRAOCCULAR GASES

6. 2. SULFUR HEXAFLUORIDE :
• It is an expansile gas. Nitrogen from the surrounding tissues diffuses into the gas bubble
and leads to the expansion of pure gas bubble .
• Maximum expansion is after 36 hours lasts for 11 days
• it is used as 30 percent SF6 and 70% air
3. PERFLUROCARBON GASES ( C3F8 : PERFLUOROPROPANE )
• Inert , colorless , odorless and inflammable gases .
• 6 times heavier than air
•As the length of the carbon chain increases the water solubility of the gas decreases .
It is this property that accounts for greater expansion and longevity of these gases with
increasing molecular weight

7. Non expansile expansile
Air SF6
Nitrogen C4F10
Helium CF4
O2 C2F6
Argon C3F8(perfluropropane)
Xenon,krypton C4F10

8. Characteristic of gases
Two major properties of gases which help in keeping the retina attached are :
Surface tension :
- Gases have highest surface
tension among all vitreous
substitutes
- -if the bubble is larger than the
break then the surface tension
prevents it from passing through
the breaks
Buoyancy : property to float
-It provides the force that pushes the
upper most retina back and thus helps
in apposition of retina to choroid

9. INDICATION :
• giant retinal tears
•internal tamponade
•Posterior breaks
•Restoration of intra ocular
volume following SRF drainage
• Total RD with multiple breaks
CONTRAINDICATION :
• large tears more than one clock hour or
multiple breaks extending over more than
one clock hour
• severe uncontrolled glaucoma
• breaks in inferior four clock hours of the
retina ,
• air travel , unable to maintain posture
postoperatively
COMPLICATION :
• rise In IOP
• lens opacities
• bullous keratopathy
• subretinal gas migration
• New break formation and vitreoretinal
traction
POST OPERATIVE CARE :
• Prone position
• Iop recording 6-8 hours post op
• Prophylactic use of antiglaucoma drugs post
op
• Performed under GA : stop NO2 15 min prior
to gas injection

10. LIQUIDS
1. Silicone Oil
•It is the only substance currently accepted for
long-term vitreous replacement
• SO are polymers of polydimethylsiloxane .The
viscosity is expressed in centistokes.
•It is transparent, immiscible with water, inert
•has a refractive index of 1.4.
•Lighter than water ( low specific gravity 0.97 )
•Higher surface tension
•The time for the removal of is around 3-6
months .

11. Mode of action:
•TAMPONADE
Acts as internal , permanent tamponade in attaching traction free retina due to high surface tension
•SPACE FILLER
Due to immiscibility with water limits free movements of proliferative cells and biochemical mediator
within vitreous cavity . Thus helps in preventing proliferative vitreoretinopathy and limits rubeosis in
PDR
•MACHANICAL INHIBITION OF MEMBERANOUS CONTRACTION
Globule of silicon oil redirects tractional forces from radial to tangential traction so detachments are
usually flat and confined to periphery sparing macula
•HEMOSTASIS
Tamponades bleeder vessels in PDR
USES
•RD in proliferative vitro retinopathy
•Giant retinal tear
•Traumatic RD

12. Complication :
•Emulsification – most common complication . Emulsified silicon oil in AC : inverse
hypopyon
•Cataract : imbalance in lens metabolism
•Glaucoma : Increased IOP is common after SO implantation. This could be caused by
pupillary block glaucoma, overfill of silicone oil, and chronic elevation due to
emulsification in the trabecular meshwork and trabeculitis
•Band shaped keratopathy
•Retinopathy : silicon retinopathy
Decreased choroidal thickness three months following SO implantation . This may be
caused by the failure of Müller cells to circulate potassium and the subsequent
potassium accumulation, retinal degeneration, and inner retinal and choroidal thinning .
•reattachment t in 20% cases

13. 2. PERFLUROCARBON LIQUIDS
• chemically and physiologically inert,
colorless and laser stable
• It has higher specific gravity allowing
it to settle posteriorly
•Low viscosity favors easy
introduction and removal
•Low surface tension
•The direct toxicity of PFCLs and their
tendency to induce inflammatory
reactions limit use of PFCL as a long-
term tamponade

14. USES PFCL :
•Displaces the subretinal fluid anteriorly which
can pass through break. Thus it helps in
flattening retina .
•It pulls peripheral retina posteriorly . Thus,
helps in visualization & dissection of
membranes in anterior PVR
•In GRT- unfolds the everted flaps.
•In removal of post. dislocated lens & IOL.
•In removal subretinal & supra choroidal
hemorrhage.

15. Complications PFCLS :
•New retinal breaks
•CRAO
•Subretinal migration
•Dispersion into Multiple bubble

16. 3. BALANCED SALT SOLUTION
•Balanced salt solution (BSS) is the most commonly used vitreous substitute.
• as irrigating solution to replace intraocular volume lost by vitreous removal intra
operatively.
•It has also been used as vehicle to carry drugs for hemostasis, pupillary dilatation and
anti-inflammatory effects.

17. NEW SUBSTITUTES
1. SEMI FLOURINATED ALKANES
• They are transparent liquids that are immiscible with water.
•They have low specific gravity than PFCLs at between 1.2 and 1.7g/cm3
•The low specific gravity (SFA) (compared to PFCLs) is thought to produce less retinal
damage .
•Higher interface tension than silicone oil may bridge larger retinal breaks
•They are well tolerated in the eye upto 3 months, but main limitations are early
emulsification and cataract formation
•They have a perfluorocarbon and hydrocarbon segments, and they are soluble in
PFCL, hydrocarbons, and silicone oils with a preferred refraction index (1.3)

18. 2. Silicone Oil/ SFA combinations
• The combination takes advantage of the high viscosity of SO and high specific gravity of the SFAs
•It produces a vitreous substitute with a good tamponade effect and lesser chance of emulsification.
•The combination of both produce either a homogenous clear solutions (heavy silicone oils) or
separated solutions (double fills) depending on the ratio of the two liquids.
• maintain a regular filling and to avoid the “egg effect”: in this case the separation of the two
substances into two phases interrupts the correct tamponade effect
3. Heavy Silicone Oil (HSO).
•Heavy silicone oil is a tamponade agent formed from a mixture of SO and partially fluorinated octane
(PFA) that is heavier than water.
• For this reason, it has been used for complex retinal detachment involving the inferior part of the
retina complicated by proliferative vitreoretinopathy.
•a good intraocular tolerance of HSO and no significant emulsification
•Complications of HSO include cataract, anterior segment inflammation, emulsification, and elevated
IOP
•The heavy SO may remain strictly adherent to the retina surface (“sticky oil phenomenon”) causing
inflammation and tissue reactivity

19. Viscosity Surface tension Specific gravity
Silicon oil High High 0.97
PFCLS Low Low 1.9
SFAS High Higher than silicon 1.2

20. EXPERIMENTAL SUBSTITUTES

21. Natural Polymers.
HYALURONIC ACID (HA) : great biocompatibility but due to the short degradation time
they cannot be used as intraocular tamponades.
COLLAGEN DERIVATIVES, such as gelatine, polygeline, and methylated collagen types I-
II,poor results
THE INTRAOCULAR GEL HYLAN : an interesting short-term vitreal substitute for its
stability and composition. Its excessive water solubility made it at the moment not
available for clinical experiments

22. Hydrogels.
Cross-linked hydrogels are synthetic polymer networks that are expanded throughout their
volume by water.
Hence , they can melt in water without dissolving.
Hydrogels have favourable properties such as transparency, biocompatibility, and mechanical
flexibility which have led to their widespread application in ophthalmology as soft contact
lenses, intraocular lenses, drug delivery systems, and adhesion for wound repair
Hydrogels can be divided into hydrogels and “smart hydrogels.” Smart hydrogels can create a
three-dimensional structure in response to a variety of signals including pH variation,
temperature, light, pressure, chemicals, and electric field

23. Transplant and Implants.
Many years ago, some authors described the first attempt to transplant vitreal tissue .
They observed that, if correctly stored, the vitreous body could maintain its structure
and also its enzymatic properties. The implanted tissue showed a degradation time
on the host, with a low inflammatory reaction and interesting surgical results on 40%
of patients. Cataract, glaucoma, and more severe adverse events until ocular atrophy
were described
IMPLANTS : artificial capsular bodies, made of silicone rubber elastomer and filled
with a saline solution, silicone oil, controlled using a valve system. The presence of a
filled capsule reduces the toxic effect, such as intraocular toxicity, emulsification, high
IOP, and keratopathy

24. Vitreous Regeneration.
The challenge to create a new vitreous with the critical 3D structure might be very
interesting and for this purpose different studies were performed.
Controlled hyalocytes proliferation with specific growth factors (bFGF stimulates and
TGF-B1 inhibits) and the production of HA with related components were evaluated
Reverse transcriptase polymerase chain reaction (RT-PCR) analyzed and compared the
expression profiles for several genes in the human vitreous tissue-derived cells.