3. HISTORY
• Viscosurgery was a term coined by Balazs
• Sodium Hyaluronate was 1st used in
ophthalmic surgery as viscoelastic in 1972 as a
replacement for vitreous & aqueous humor
4. IDEAL VISCOELASTIC
• Ease of infusion
• Retention under +ve pressure in eye
• Retention during phaco
• Easy removal/no removal needed
• Doesnt interfere with instruments/IOL placement
• Protects endothelium
• Nontoxic
• Does not obstruct aq.outflow
6. VISCOELASTICITY
• Elasticity refers to the ability of a solution to
return to its original shape after being stressed
• Elasticity allows the anterior chamber to
reform after deformation by depression on the
cornea when external forces are released.
7. VISCOSITY
• Viscosity reflects a solution's resistance to flow,
• A function of the molecular weight of the
substance.
• Viscosity of OVDs is measured in centipoise
(cPs) or centistokes (cSt), which are measures
of the resistance to flow relative to a given
shear force.
• The higher the solution's molecular weight,
the more it resists flow
8. PSEUDOPLASTICITY
• Pseudoplasticity refers to a solution's ability to
transform when under pressure, from a gel-like
substance to a more liquid substance
• More pseudoplastic a material is, the more
rapidly it changes from being highly viscous at
rest to a thin, watery solution at high shear
rates.
9. SURFACE TENSION
- The coating ability of an OVD is determined not
only by the surface tension of material itself but
also by the surface tension of the contact tissue,
surgical instrument or IOL.
- By measuring the angle formed by a drop of
OVD on a flat surface (contact angle),the
coating ability is estimated.
- At lower surface tension & lower contact
angle, better ability to coat.
11. SODIUM HYALURONATE
• Biopolymer, disaccharide
• occurring in many connective tissues throughout
the body, including both the aqueous and vitreous
humors
• Hyaluronate has a half-life of approximately 1 day
in aqueous and 3 days in vitreous.
• Mainly present in visco cohesives
12. CHONDROITIN SULFATE
• Chondroitin sulfate (CDS) is another
viscoelastic biopolymer that is found as one of
the three major mucopolysaccharides in the
cornea.
• Obtained from shark fin cartilage
• Eliminated from the anterior chamber in
approximately 24 to 30 hours
• Coats tissues but poor space maintainer
13. HYDROXYPROPYL METHYL CELLULOSE
• Does not occur naturally in animals but is
distributed widely in plant fibers
• Easy availability
• Ease of preparation
• Storage at room temperature
• Ability to with stand autoclaving
• Main component in dispersives
15. CLASSIFICATION OF OVDS
High viscosity-cohesive OVDs
Lower viscosity-dispersive OVDs
Viscoadaptive OVDs
1
2
3
16. COHESIVES VS DISPERSIVES
COHESIVES DISPERSIVES
High viscocity Low viscocity
Low mol wt High mol wt
Long chain molecules Short chain molecules
Adhere to themselves through
intramolecular bonds, resists
breaking apart.
They adhere well to external
surfaces, e.g., tissues and
instruments.These materials
tend to break apart easily
High degree of pseudoplasticity
and high surface tension
Lower surface tension and
lower pseudoplasticity
20. • All products contain Na.hyaluronate
• Indications of highviscous cohesive OVD-
-To deepen the AC
-To enlarge small pupils
-to dissect adhesions
-during IOL implantation
21. ADVANTAGES
1.Maintain space at low shear rates
2.Easily displaced at high shear rates
3.Sticks together,aspirated out easily
4.Low risk of post op IOP rise even if retained
DISADVANTAGES
1.Minimal coating,so less endothelial protection
22. LOWERVISCOSITY-- DISPERSIVES
MEDIUM VISCOCITY VERY LOW VISCOCITY
1.Viscoat
2.Vitrax
3.Cellugel
4.Biovisc
1.Occucoat
2.Ocuvis
3.I-cell
4.Hymecel
5.Viscilon
Most of them are Hydroxypropyl methyl cellulose
23. ADVANTAGES
1.Excellent coating and gives superior endothelial
protecton
DISADVANTAGES
1. Complete removal of dispersive OVDs is
difficult because the molecules do not tend to
join together and do not aspirate as a unit,
2. Do not maintain or stabilise spaces
3. Can form microbubbles and obscure view
4. High risk of post op IOP rise
24. VISCOADAPTIVES
• Behaviour changes at different flow rates
• Acts as a viscous cohesive agent at lower flow
rate & as a pseudo-dispersive agent at higher
flow rates
• Adapts its behaviour to surgeon’s needs during
surgery
• Highly purified non inflammatory high mol.wt.
Na Hyaluronate at a 2.3% conc. dissolved in a
physiological buffer
• Example HEALON 5
25.
26. ADVANTAGES
• 1. Crystal clear & has higher refractive index than
aq.humor, so increases clarity within surgical field.
• Ability to bind to & to protect delicate corneal endoth.
cells from debris & turbulence during phaco
• Helpful in small pupil as it causes viscomydriasis
• Neutralises the +ve vitreous pressure & prevents the
capsulorrhexis extension
DISADVANTAGES
1.Risk of post op IOP rise if retained
27.
28.
29. CLINICAL USES
Cataract surgery
• Protection of endothelium
• Maintaining of AC
• CAPSULAR RHEXXIS
• Cleavage of lens structure
• Visco ecpression of lens
• Phacoemulsification of nucleus
• IOL implantation
• dilate the pupil & maintain a good intraoperative
mydriasis
30. SOFT SHELL TECHNIQUE
• Developed by Arshinoff
• Use of both lower viscosity dispersive & high
viscosity cohesive OVDs together to minimise
their drawbacks & to get best properties of both
35. USES
• Floppy iris syndrome,the soft-shell technique can
hold the iris in place throughout the surgery.
• cases of broken zonules, the dispersive OVD can
compartmentalize the eye and keep vitreous
pushed posteriorly, while the cohesive OVD keeps
the anterior chamber formed and pressurized.
• highly myopic eyes, dispersive OVDs protect the
cornea, while re-application of cohesive OVDs to
pressurize the anterior segment can minimize
traction on the vitreous base and decrease retinal
risk
36.
37. GLAUCOMA SURGERY
Visco-canalostomy
• Means opening of schlemm’s canal by OVD
• A Nonpenetrating procedure ,independent of
external filtration
• Advantages-decrease risk of infection,
-decrease incidence of cataract
-hypotony
-flat AC
-Excludes risk of late infection & conjunctival
& episcleral scarring
• Healon GV and healon5 are used
38. KERATOPLASTY
• Used to fill the AC before removing corneal button from
donor eyes as it helps to protect corneal endothelium
and provides an even and circular trephination
• In recipients eyes helps to have even and circular
trephination,protects other intraocular structures
maintains IOP and prevents sudden collapse of AC
during trephination
• In lamellar keratoplasty helps in the dissection of deep
stroma during dissection of recipients stroma,called
viscodelamination of cornea
40. • In strabismus sx Force required to bring the muscle
to its insertion is significantly less with the use of
subconjunctival viscoelastic
• In plastic surgery during DCR helps in identifying
lacrimal sac
• Viscoelastics have a role in canalicular repair
where the uninjured canaliculus is irrigated with
fluorescein dye tinted viscoelastic , that spills from
the other end ; helping to locate the proximal end
of the injured canaliculus
• In AS trauma helps to separate salvageable tissues
from damaged tissues during sx
41. RECENT USES
VISCOSTAINING OF CAPSULE
• Techniques-staining from above under an air
bubble & intracameral subcapsular inj.of Fl.Na (
staining from below)with blue-light enhancement.
• Any instrument entering eye will cause some air to
escape with rise of lens-iris plane
• A small amount of high density viscoelastic placed
near incision prevents air escape & minimizes risk
of sudden collapse.
• Alternatively-dye mixed with OVD called as
viscostaining of ant.lens capsule covers ant capsule
without coming in contact with corneal endoth.
42. VISCO ANASTHESIA
• Mixture of OVD with an anesthetic soln (known
as VISTHESIA) had advantages of viscosurgery,
maintainence of ACD, capsular bag expansion,
protection of corneal endothelium.
• Prolongs anesthesia
• No extra surgical step for intracameral inj. Of
lidocaine
• Contains topical component -0.3% hyaluronic
acid with 2% lidocaine in a single dose unit
• Intracameral component-1.5%hyaluronic acid
with 1% lidocaine
43. REMOVAL OF OVD’S
-Rock & Roll method
-Two compartment technique
-Bimanual irrigation & aspiration technique
44. COMPLICATIONS OF OVD USE
• Post-op. increase in IOP
- Occurs in 1st 6-24 hrs & resolves
spontaneously within 72 hrs
- Due to mechanical resistance at TM
• Crystallization of IOL surfaces
- Due to precipitation or deposition of
viscoelastic soln.
- Fern like or amorphous appearance
- IOL should be explanted & exchanged
45. Capsular block syndrome or Capsular bag
distension syndrome (CBS)
Characterised by accumulation of liquefied
substance within a closed chamber inside the
capsular bag, formed because the lens nucleus or
the PCIOL optic occludes the ant. capsule opening
created by capsulorhexis
• Classified as :
1.Intra-op – time of nucleus luxation following
hydro-dissection
2.Early post-op
3.Late post op. – with liquefied after cataract
46. • eg.Use of high density viscoelastic agent like
Healon GV causes late CBS
• Reduced distance visual acuity and improved
near acuity due to induced myopia :forward
shift of IOL.
• IOP is normal, despite shallow anterior
chamber.
• Treatment is done by yag laser application to
anterior capsule to allow OVD to escape
anteriorly or posterior capsule may be lasered
with escape of OVD posteriorly.
47. Pre treatment - Accumulation of turbid
fluid in the space between IOL and
posterior capsule
Pre treatment UBM - UBM showing in
the bag IOL and posterior bowing of
posterior capsule
Post treatment UBM - UBM confirming
disappearance of retro IOL space following
YAG laser
Post treatment - Following YAG laser
capsulotomy disappearance of turbid fluid
48. • Calcific band keratopathy
- Occurs with chondroitin sulphate containing
OVDs
• Pseudo Anterior uveitis
- Due to OVDs viscous nature & the electrostatic
charge of it
- RBCs & inflammatory cells remain in AC giving
it appearance of uveitis
- Spontaneously resolves within 3 days
- Intra ocular hemorrhage may be trapped
between vitreous space & OVD in AC mimicking
VH
