Hydration stability of intracorneal hydrogel implants

A hydrogel intracorneal lens for refractive keratoplasty must have predictable and stable optics when implanted in the corneal stroma. A series of experiments was performed to evaluate the hydrogel hydration stability when in the corneal stromal environment. Hydrogel ICLs of 54%, 63%, 66% and 71% water content showed no loss of hydration (by weight) after one week in the rabbit corneal stroma. In vitro experiments with hydrogel discs of 56%, 65%, 69.5% and 75% water content were subjected to swelling pressures ranging from 55 to 150 mmHg in a suction chamber. Only the hydrogel of 75% water content showed a significant loss of hydration at the physiologic swelling pressure of 55 mmHg. This study shows that hydrogel materials with up to 69.5% water content can be expected to be dimensionally stable when used in keratorefractive surgery.