Histopathological study of experimental intrapalpebral injection of hyaluronic acid gel

Abstract

Hyaluronic acid gel (HAG) fillers are successfully used in the treatment of many eyelid disorders. It is considered that the effect of HAG injection lasts for 6 months on average. However, in our experience volume augmentation persists longer, suggesting that the presence of the filler in the eyelid may be associated with certain tissue reactions. The objective of the study was to investigate morphological features of HAG biodegradation. Seven adult Chinchilla rabbits (14 eyes) received a single 0.1 ml HAG (Restylane, Q-Med AB, Sweden) subcutaneous upper eyelid injection followed by contouring of the skin for 1.5 mm on average. Tissue samples containing HAG were collected for histopathological examination with morphometric analysis on day 0, week 2, months 1, 2, 4, 6, and 9. HAG persisted subcutaneously in the eyelid during the 9 months of the study in the form of a sponge-like structure with compartments of varying shape and size. Its total volume diminished gradually, nevertheless at the end of the study the filler could still be found in some compartments, mainly peripheral. In the central area of the depot residual HAG was surrounded by optically transparent spaces. After being injected subcutaneously into the eyelids of experimental animals HAG formed a sponge-like structure causing a significant increase in eyelids volume. Gradual biodegradation of HAG was accompanied by neocollagenogenesis and 9 months later the process was still ongoing.