[Experimental study of hyaluronic acid gel fillers biodegradation in orbit].

Introduction: Recently, hyaluronic acid gel (HAG) fillers were proposed as an effective alternative treatment option for surgical orbital volume augmentation. Several authors reported about long-standing effect of the filler.
Purpose: To assess the features of HAG biodegradation after intraorbital injection in experimental environment.
Material and Methods: In the course of the experiment, 7 chinchilla rabbits (14 eyes) received a single 1ml intraorbital HAG injection (Restylane SubQ, Galderma, Sweden) using a cannula. The animals' orbits were examined by ultrasound scan after the injection and at 1, 3, 6, 9, 12 and 18 months. The animals were subsequently sacrificed for morphological study of orbital tissue containing the HAG filler.
Results: The HAG filler persisted in the orbit of experimental animals during the whole follow-up period. The volume of HAG depot and its density diminished gradually till the 18th month, after which the particles of HAG could still be detected with the morphological study and ultrasound.
Conclusion: The HAG filler persisted in the orbit of experimental animals up to 18 months. Incomplete biodegradation explains the longstanding duration of the injection effect.