Viscoelastic protection from endothelial damage by air bubbles

Purpose: To determine whether viscoelastic materials effectively protect the corneal endothelium from air bubbles. Setting: Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea. Methods: Human eye-bank and rabbit eyes had a standardized phacoemulsification procedure with or without viscoelastic material (Healon® [sodium hyaluronate 1.0%], Healon GV® [sodium hyaluronate 1.4%], or Viscoat® [chondroitin sulfate 4.0%-sodium hyaluronate 3.0%]). The integrity of the endothelium was examined after the procedure with F-actin staining and scanning electron microscopy. Rabbit eyes with and without viscoelastic material (Healon or Viscoat) had a standardized irrigation/aspiration (I/A) procedure. The mucinous layer of the endothelium was examined after the procedure with transmission electron microscopy. Results: In the phacoemulsification experiment without viscoelastic material, with Healon, and with Healon GV, the endothelium of human and rabbit corneas had many areas of cell loss in a pattern consistent with air-bubble damage. With Viscoat, endothelial cells remained intact. In the I/A experiment, the mucinous layer of Viscoat-exposed rabbit endothelium appeared thinner. In the same experiments without viscoelastic material or with Healon, the mucinous layer of the endothelium appeared normal. Conclusions: Viscoat effectively protected the endothelium from air-bubble damage. Viscoat appears to protect the endothelium by acting as a physical barrier. Its adherence is probably related to the way it interacts with the mucinous layer of the endothelium.