Prevention of vitreous loss.

Retrobulbar anaesthesia, digital massage, osmotic therapy, and acetazolamide are frequently employed in various combinations to effect ocular hypotony before cataract extraction.* It is believed by many that hypotony prevents vitreous loss during this operation. t Profound akinesia to preclude extraocular muscle contraction and resulting shortening of the scleral shell is a clinically accepted mechanism to prevent vitreous loss (Kornblueth, Jampolsky, Tambler, and Marg, I960). Another clinical and laboratory-proved method is the induction of acute hyperosmolarity.4 Though digital massage induces immediate vitreous weight reduction in the closed rabbit eye, recent investigations have demonstrated a rebound phenomenon which increases both vitreous weight and intraocular pressure approximately 5 to Io min. after the completion of massage (Obstbaum, Robbiins, Best, and Galin, 197I). This time sequence would, of course, be totally undesirable during a lens extraction. Experiments concerning the effects of hyperosmolarity and digital massage have been carried out on the closed eye which, though of significant clinical importance, is not comparable to an eye undergoing lens extraction. Consequently, this investigation was undertaken to evaluate the effects of digital massage and 20 per cent. mannitol infusion on vitreous weights in rabbit eyes that had undergone the initial steps of lens extraction.