VISCO-ELASTIC SUBSTANCES

Properties :

  1. Chemically :
    • Inert
    • Iso-osmotic
    • Sterile
    • Free from particulate matter
    • Non pyogenic
    • Non-toxic
    • Non antigenic
  1. Optically clear
  2. Elasticity : resist deformation & maintain shape
  3. Viscosity should be enough to provide sufficient space for manipulation within the eye.
  4. Hydrophilic & dilutable properties – to irrigate the material out of the eye post-op
  5. Protectability & maintenance of space :
    • should protect endothelium
    • separate the tissue
    • maintain the space
    • acts as a lubricant
    • easy to inject

 

 TYPES :

  • Intraocular preparations :
    1. HPMC : Hydroxy Propyl Methyl Cellulose
    2. Hypromellose
    3. Sodium Hyaluronate
    4. Chondroitin Sulfate

 

  • Eye drops :
    1. HPMC
    2. PolyVinyl alcohol ( 1.4% )
    3. Povidone ( 0.6% )

 

Sodium Hyaluronate

  • Highly visco elastic
  • Non inflammatory
  • Very expensive, hence restricted usage cf HPMC

Hypromellose

  • Viscous substance similar to HPMC.

Chondroitin Sulfate

  • Similar to Sodium hyaluronate

 

USES :

  1. To maintain anterior chamber.

If not maintained,

↓

frequent intra operative A/C collapse

↓

endothelial damage by the instruments used intra operatively

↓

affecting Na2+ – K+ pump of endothelium

↓

post operative corneal edema

  1. Protect corneal endothelium.
  2. Preventing entry of blood & fluid in the anterior chamber.

 

Steps when used in Cataract Surgery:

  1. After making side port using 15° Lance tip blade ( if surgeon not using methylene blue dye )
  2. During CCC ( continuous curvilinear capsulorrhexis )
  3. Nucleus delivery : Visco expression technique from main site of incision.
  4. After nucleus delivery : to form A/C & capsular bag to place IOL.

P.S. : It is important to wash visco after surgery is over else:

  1. it will block trabecular meshwork, secondary rise in intra ocular pressure ( not glaucoma ,since it’s for few days only )↓

    which can give rise to corneal edema

    ↓

    Mx : T. Acetazolamide 250mg QDS x 4-5 days with K+ supplement ( coconut water – advisable in Diabetics / banana- contraindicated in Diabetics )

    Topical : Timolol eyedrops in IOP <30

    Timolol + Dorzolamide/brinzolamide if IOP>30mmHg

    Never use Prsotagladin/pilocarpine , because its associated with secondary inflammation which can worsen

  2. post operative intra ocular inflammation
    • Mx: T. Prednisolone (1mg/kg), total dose to be taken in morning after breakfast along with T. Ranitidine (150mg) BDS or T.Omeprazole (20mg) taken half hour before breakfast since steroids leads to severe gastritis on empty stomach.
    • Topically potent Steroid drops: Difluprednate 0.1%, widely used nowadays, QDS
    • Prednisolone acetate : 1 hourly
    • Steroids, systemic or topical, are to be tapered once desired result is obtained. Never stop abruptly.