Hyaluronan polymer size modulates intraocular pressure.

To investigate whether the occasional increase in intraocular pressure that may arise following injection of sodium hyaluronan into the anterior segment during intraocular surgery is related to the polymer size of hyaluronan, controlled fragmentation of hyaluronan chains in vitro was obtained using progressive incubation with testicular hyaluronidase. The profile of molecular sizes of the hyaluronan polymers in various preparations was determined using molecular sieve column chromatography. Individual preparations were injected into six rabbit eyes and intraocular pressures were measured every one-half hour for 12 hours. Longer incubations of hyaluronan with hyaluronidase resulted in more extensive degradation with accumulation of shorter chain lengths. In the rabbit, mean intraocular pressure for 12 hours following intracameral injection of hyaluronic acid (HA) is proportional to the polymer size of HA. The occasional elevation of intraocular pressure that occurs following injection of hyaluronan during ophthalmic surgery can be avoided in part by assuring the rapid fragmentation of the large molecular size hyaluronan polymer.