Viscoelastics for Cataract Surgery
Viscoelastics can be divided into 2 types:
  • Cohesive with high molecular weight, high surface tension, for example Healon. It tends to be big and bulky and do not coat tissue.

  • Dispersive with low molecular weight, low surface tension, for example: Viscoat. It is smooth and likes to coat others
There is a spectrum ranging from most cohesive to most dispersive.

Viscoat and Ocucoat (most dispersive)....Provisc...Amvisc...Amvisc plus...Healon....Healon GV (most cohesive)

Advantages and disadvantages.

  • Cohesives best for maintaining anterior chamber, capsulorrhexis and creating space. Easy to remove because of high surface tension. Can lose a large amount through wound during capsulorrhexis if the wound is open. Tend to go away with the first vacuum. Do not protect endothelium well.

  • Adhesives best for protecting the corneal endothelium, sealing capsular tear and keeping iris at bay. Do not maintain space well. Attract particles to endothelium and increased risk of burn.
Note: Both cohesive and dispersive can be used together during cataract surgery. In the 'soft shell' technique, dispersive is first injected to coat the endothelium and cohesive injected next to fill the anterior chamber. This improves endothelium protection in cornea with low endothelium count.
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