[Principles of the practical use of viscoelastic substances in eye surgery].

The different rheological properties of viscous and viscoelastic substances indicate different uses in surgical practice. Purely viscous substances solve manly surface-tactical problems. The stronger the elastic component, the better the substances are suitable also for space-tactical and tissue-tactical purposes. A new field of interest is the neutralization of the buoyancy of silicone oil and gas bubbles. The latter can be used for the insertion of posterior chamber lenses in cases where the lens capsule is lacking (air sandwich). The main disadvantage is the postoperative rise of intraocular pressure: but this can be managed by a release of the substance through a preplaced keratotomy.