Ophthalmic Viscoelastic devices

1. OPHTHALMIC VISCOSURGICAL
DEVICES
Dr Binesh Tyagi
Fellow - Phaco Refractive Dept
NDSSEH

2. RECENT DNB Qs
Dec 2013
• Broadly classify viscoelastic substances. What is soft shell
technique? Important precautions in phaco with low
endothelial counts?
(2+4+4)
June 2012
• What are viscoelastics? Classification? Indications of each?
Side effects? (1+3+4+2)

3. HISTORY
• In 1970s the move from ICCE to ECCE resulted in increased
number of post operative corneal decompensations that
needed full thickness corneal grafts.
• Dr Endre A Balazs introduced viscoelastics and coined term
Viscosurgery
• He worked on structure and biological activity of
hyaluronan, a viscoelastic substance present in all tissues.
• Sodium hyaluronate was 1st used in ophthalmic surgery as
viscoelastic in 1972 as a replacement for vitreous &
aqueous humor.
• Swedish Pharmacia AB patented it and introduced HEALON

4. INTRODUCTION
SUBSTANCES HAVING DUAL PROPERTIES
1.VISCOCITY OF FLUID
2.ELASTICITY OF GEL OR SOLID

5. IDEAL VISCOELASTIC
• Ease of infusion
• Retention under +ve pressure in eye
• Retention during phaco
• Easy removal
• Doesn't interfere with instruments/IOL placement
• Protects endothelium
• Does not obstruct Aqueous Outflow

6. IDEAL VISCOELASTIC PROPERTIES
• Non toxic
• Nonpyrogenic
• Non inflammatory
• Nonimmunogenic
• Sterile
• Inert and iso-osmotic
• Optically clear
• Contaminant free , particle free
• Should have a pH similar to AC
• Cost effective
• Should not interfere with wound healing

7. RHEOLOGICAL PROPERTIES
 Viscosity
 Pseudoplasticity
 Elasticity
 Coatability
 Cohesiveness
 Dispersiveness

8. VISCOSITY
• Viscosity reflects a solution's resistance to flow
• Internal friction caused by molecular attraction - leads to solution’s
resistance to flow
• The higher the solution's molecular weight, the more it resists flow
• 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.
• High viscosity solutions tend to stay in the AC and separate the tissues well
• Shear force/rate- stress that is applied parallel to the material

9. ELASTICITY
• It refers to ability of a substance or material to return to its original shape
after being deformed (stretched or compressed)

10. 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. COATABILITY /LUBRICATING
POWER
• It measures the adhesion capacity of OVD
• It is inversely proportional to surface tension and the contact angle b/w
OVD and a solid material
• Low surface tension, low contact angles, more negatively charged OVDs
better coat the endothelium
• HPMC, Chondroitin Sulphate > Na Hya.

12. PSEUDOPLASTICITY
• Pseudoplasticity AKA rheofluidity refers to a solution's ability of the
solution to transform from gel like state into liquid like state(viscosity
reduces) under pressure ( shear force )
• 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.
• This property enables easy injection and removal of an agent
Low shear Medium shear High shear
Substance at rest Eg: Instruments
movement in eyes
Substance under force
Viscosity increases Viscosity decreases
Gel form Liquid form

13. COHESIVENESS
• It is the degree to which the material adheres to itself .
• It depends on molecular weight, strength of molecular
binding and elasticity.
• The more cohesive an OVD, the lower the flow rate and
hence they are good for space maintaining and are
easily removed.

14. DISPERSIVENESS
• It is the tendency of a material to disperse when injected
into AC
• Its is defined as percentage of viscoelastic agent
aspirated/100mm Hg
• The higher the CDI , the quicker the substance can be
aspirated when a certain amount of aspiration is reached
COHESIVE DISPERSIVE INDEX

15. COMPOSITION
Viscoelast
ics
Hydroxy
propyl
methyl
cellulose
Chondroit
in Sulfate
Sodium
Hyalurona
te
Others

16. SODIUM HYALURONATE
• It is a glycosaminoglycan and long-
chain polymer of disaccharide units of Na-
glucuronate-n-acetylglucosamine
• Occur in many connective tissues
throughout the body, including both
the aqueous and vitreous humors
• Hyaluronate has a half-life of
approx1 day in aqueous, 3 days in
vitreous.
• Mainly present in visco cohesives

17. CHONDROITIN SULFATE
• Sulfated glycosaminoglycan (GAG)
• A chain of alternating sugars (n-
acetylgalactosamine and glucuronic acid)
• Found as one of the three major
mucopolysaccharides in the cornea.
• Obtained from shark fin cartilage
• Eliminated from the anterior chamber in
approx 24 to 30 hours
• Coats tissues but poor space maintainer

18. 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

19. OTHERS
• Ocugel
• Combination of HPMC and chondroitin sulfate
• Offers better viscosity and coating.
• As the viscoelasticity is much less it requires a large bore cannula for
insertion and aspiration ability.
• Collagen
• Derived from Human placental collagen (type IV)
• 2 percent solution is obtained as supernatant after centrifugation for
removal of fibrillar material.
• a protein whereas the other viscoelastic substances are
polysaccharides.
• Cellugel
• synthetic polymer of modified carbohydrate
• Advantages it can be autoclaved, does not require refrigeration, and
may be stored at room temperature for two years. It can be injected
with a 25 gauge cannula.
• Newer viscoelastics

20. CLASSIFICATION
• High Viscosity cohesive
• super viscous cohesive(>1,000,000mPs)
1.Healon GV(1.4%), 2.Ivisc plus
• Viscous Cohesive; OVD(bet 1,000,000and
10,000)
1.Ivisc, 2.Provisc, 3.Healon(1%), 4.Amvisc
• Lower viscosity dispersive
• Medium viscosity
1.Viscoat, 2.Vitrax, 3.Cellugel, 4.Biovisc
• Very low viscosity
1.Occucoat, 2.Ocuvis, 3.I-cell, 4.Hymecel, 5.Viscilon
• Viscoadaptive(Healon-5)

22. COHESIVE
• High viscosity
• Able to give pressure to the eye
• Create and maintain space
• They act like a gel
• High mol wt
• Long chain molecules
• Adhere to themselves through intramolecular bonds, resists breaking
apart.
• High degree of pseudoplasticity and high surface tension

23. Advantages of Cohesive OVDs Disadvantages
Create , deepen and maintain space in
AC
Come out of the eye easily as a whole
during surgery under intense vitreous
pressure
Clear vision , transparency Do not stay attached to corneal
endothelium
Ideal for flattening of AC for Rhexis Some of the substances have high risk
post OP raised IOP if not completely
removed ( Healon 5 )
Ideal to open capsular bag for IOL
insertion
Unwillingly removed due to fluidic
movements during phaco surgery
They enlarge and stabilize the size of the
pupil
Easy to remove at the end of the
procedure
Eg: Healon , Healon GV , Provisc , Amvisc

24. DISPERSIVE
• Low viscosity
• Ability to coat intraocular structures
• The molecules behave separately and build up a solution.
• They tend to stay in fluidic movements of phaco surgery
• Low viscosity
• Low mol wt
• Short chain molecules
• They adhere well to external surfaces, e.g., tissues and instruments.
• These bonds tend to break apart easily
• Lower surface tension and lower pseudoplasticity
Eg: HPMC, Dispersive Na Hyaluronate

25. Advantages of dispersive OVDs Disadvantages
Ability to coat the intraocular
structures
Low viscosity dispersives do not
maintain spaces well
They separate the spaces. They
hold vitreous back in case of weak
zonules or in case of PC rent
May have air bubbles inside or
form microbubbles during surgery
Ability to lubricate IOL and injector Difficulty to remove at the end of
procedure
They fragment into small pieces
during irrigation and aspiration and
this may obscure the visualisation
of PC during surgery
Eg: Vitrax, Viscat , OcuCoat

26. COHESIVE DISPERSIVE

28. VISCOADAPTIVES
• Behaviour changes at different flow rates
• viscous cohesive agent at lower flow rate
• 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

29. USES

30. CATARACT SURGERIES
• Protection of epithelium
• Protection of endothelium
• Control of capillary oozing
• Maintaining AC
• Capsular rhexis
• Cleavage of lens structure
• Visco expression of lens
• Phacoemulsification of nucleus
• IOL implantation
• Dilate the pupil & maintain a good intraoperative mydriasis
• Iris herniation or prolapse
• Pediatric cataract Sx – while performing capsulorhexis

32. 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

33. SOFT SHELL TECHNIQUE

35. ULTIMATE SOFT SHELL
TECHNIQUE (USST)
• Uses viscoadaptive and BSS (instead of dispersive).
• Makes all cases much easier, and more stable.

37. SST-USST COMBINATIONS ( TRI-
SOFT SHELL TECHNIQUES)
• Use layers of
• dispersive against the cornea,
• Cohesive centrally to establish stability,
• BSS (Or XYLO-PHE) on the lenticular surface (for a Low-viscosity surgical
space).
• Optimizes pupil dilation.

38. TRI SOFT SHELL TECHNIQUE

39. USES- SOFT SHELL TECHNIQUE
• Floppy iris syndrome-
• 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

40. GLAUCOMA SURGERY

41. Visco-canalostomy
Means opening of schlemm’s canal by OVD
A non penetrating procedure ,independent of external filtration
Advantages-
-Decrease incidence of cataract
-Hypotony and flat AC
-Excludes risk of late infection & conjunctival & episcleral scarring
Cyclodialysis
To achieve a small cyclodialysis, OVD can be injected between sclera and
ciliary body around the edge of the cleft.
The abandoned cyclodialysis operation could be reintroduced in aphakic and
pseudophakic eyes, using the tissue separating and space maintaining
properties of viscoelastic substance.

42. 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.

43. POSTERIOR SEGMENT SURGERIES
• Replace diseased vitreous
• Reattach & provide temporary tamponade in retinal holes and detachments
• Reattach giant retinal tears
• Restore IOP after release of subretinal fluid
• Maintain IOP after vitrectomy
• Achieve surgical dissection of membranes
• Protect corneal endothelium during gas injection in Aphakic eyes
• Separate membranes from lens or retina
• To protect against possible inflammation, use of steroid therapy, sub-tenon
injection at the End of surgery, or administration of systemic Steroid is indicated.

44. TRAUMA
• Anterior segment in primary trauma
• sorting out of the traumatized tissues and their separation
from each other
• hopelessly crushed tissues are removed and the salvageable
ones are reposited and sutured.
• Thus a deliberate and orderly reconstruction is possible,
making secondary procedures less frequent and simple.
• In posterior segment injury
• the collapsed globe can be restored to a near normal shape
• intraocular pressure can be raised to a level where a careful
evaluation of the situation and restoration of the wall of the
eye is possible.

45. • In strabismus sx
• Significantly less force required to bring the muscle to its insertion with the
use of subconjunctival viscoelastic
• coating of extraocular muscles lead to during surgery with viscoelastic
cushion indicate a significant decrease of scarring of the epimuscular tissue.
• During repeated probing and irrigation of the lacrimal drainage
system in elderly, if the passage is filled with viscoelastic substance
the patency can be expected to be maintained from one month to
six months
• 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
EXTRA OCULAR PROCEDURES

46. 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.

47. VISCO ANASTHESIA
• Mixture of OVD with an anaesthetic (known as VISTHESIA®) had
advantages of viscosurgery( maintenance of ACD, capsular bag
expansion, protection of corneal endothelium)
• Prolongs anaesthesia
• 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

48. REMOVAL OF OVD’S
-Two compartment technique
-Rock & Roll method
-Bimanual Irrigation & Aspiration technique

49. 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 Trabecular Meshwork.
• Crystallization of IOL surfaces
- Due to precipitation or deposition of viscoelastic soln.
- Fern like or amorphous appearance
- IOL should be explanted & exchanged

50. 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

51. • 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.

52. 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

53. • 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 haemorrhage may be trapped between vitreous space &
OVD in AC mimicking Vit h’ge.