Vitreous Substitutes 153053

VITREOUS SUBSTITUTES 1) 2) 3)

4) 5) 6)

Gases (Air and others) Silicon Oil Fluoro Silicon oil PFCL Ringer lactate Sodium Hyaluronate (Healon 1%)

PROPERTIES RL

Air

Gas

Silicon oil

PFSilicon oil

PFCL

Healon 1%

Sp. Gr.

Water

-

-

0.97

1.25

1.9

1.006

Buoyancy

Nil

High

High

Moderate

Settling

Settling

Settling

Conf. to surface

Good

Good

Good

Moderate

-

-

-

Viscosity

Water

-

-

5000 cs

300 cs

2.6 cs

200,000 cs

Surface tension

-

High

High

Moderate

Solubility in water

-

Nil

Nil

Nil

Nil

Nil

Yes

Visibility

Good

Poor

Poor

Moderate

Good

Good

Good

Endolaser

-

-

-

Yes

Yes

Yes

Yes

Moderate Moderate

Moderate

GASES Air

SF 6

C2F6

C3F8

Expansibility

Nil

Double

Triple

Quadruple

Longevity

3 days

10 days

35 days

55 days

Non expansile Concentration

-

30 %

16 %

14 %

3 days

3 days

Max. Expansion Immediate 36 Hours

Internal Tamponade Air

5.15

Gas

5.15

Silicon Oil

0.3

PF silicon oil

1.35

PFCL

4.3

PFBL

PF Octane

Sp. Gr.

PF Decalin

PF Phen

1.94

2.05

Viscosity

2.6

0.8

2.6

8.03

Surface Tension

16

14

16

16

Boiling point

177 o C

105 o C

142 o C

215 o C

Refractive Index

1.3

1.3

1.3

1.3

Others

Contains Nitrogen

-

-

Least Toxic

SILICON OIL -

-

Linear polymers of Di-Methyl Siloxane with side group radical Greater the chain length, higher the molecular weight, greater the viscosity, lesser the inflammation and emulsification.

INDICATIONS 1) 2)

Settling of Retinal breaks Internal Tamponade of RD i. ii.

3) 4) 5)

In Vitrectomised eyes In non Vitrectomised eyes

IOP Stabilization Third hand Others

INDICATIONS 1)

Settling of Retinal breaks - The vitreous substitute requires volume larger than the break so as to occlude it. - The vitreous substitute requires surface tension so as to not enter the break.

Example 1) Unfolding of giant retinal tear – air, gas, Silicon oil, PFCL, Healon 2) Pneumatic retinopexy – air, gas - Anterior retinal break. - Less than 1 clock hour. - 8-4 o’clock. - Less than Grade B PVR. 3) Prevent fishmouthing of horseshoe tear – air, gas 4) Superior bullous RD / Unholy RDs - PFCL

Internal tamponade of RD - The vitreous substitute requires high surface tension so as to not enter the break. - The vitreous substitute requires buoyancy so as to oppose the retina. - The vitreous substitute requires to be expansile to maintain the opposition. - The vitreous substitute requires to be there for 7-8 days, atleast for retinal adhesion to occur.

Examples 1) Tractional RD with rhegmatous RD – silicon oil 2) Traumatic RD – silicon oil 3) RD with PVR – silicon oil 4) Choroidal coloboma with break – silicon oil 5) Grade 3 - Grade 4 ROP – silicon oil 6) Total RD with multiple breaks – air, gas 7) Posterior breaks – air, gas 8) Post Vitrectomy air fluid exchange – air, gas, oil 9) Post-operative air fluid exchange in vitrectomised patients with RD – air, gas

IOP Stabilisation - The vitreous substitute requires to compensate for the hypotony achieved during vitrectomy and SRF drainage – air, gas, RL, silicon oil, healon 1%, PF phenanthrene

Third hand - The vitreous substitute requires to act as an alternative instrument for retinal manipulation and stabilisation - PFCL

Examples 1) Separation of membranes in PVR. 2) Flattening of retina by rolling drainage of SRF through the retinal break.

Others - Haemostasis during vitrectomy – oil, PFCL - Suprachoroidal effusion drainage - PFCL - IOL / Lens / IOFB removal - PFCL - Vitrectomy at Vitreous base - PFCL - Prevention of Pthysis bulbi – Silicon oil

PRECAUTIONS AND COMPLICATIONS 1) 2) 3) 4) 5) 6)

Air. Gases. Silicon Oil. PFCL. RL. Healon 1%.

MISCELLANEOUS 1)

2)

Silicon oil has refractive index of 1.4, hence makes phakic and pseudo-phakic eyes +5 dioptres and aphakic eyes -5 dioptres. Arc of of a 0.3 cc gas is 90 o and 1 cc gas is 126 o.