Effects of intracamerally or subconjunctivally injected cross‐linked hyaluronic acid on the intraocular pressure and on the anterior segment of the rabbit eye

Abstract Cross‐linked hyaluronic acid (CLH), a viscoelastic substance with a high viscosity, was injected into the left anterior chamber of 5 rabbits without simultaneous withdrawal of aqueous humour. The right eyes of the same rabbits received an equal amount of sodium hyaluronate (Healon®), The intraocular pressure (IOP) of the CLH injected eyes increased four‐fold immediately after the injection. One week post injection the IOP had decreased to the pre‐injection level where it remained until the euthanatization of the animals 32 days post injection. Biomicroscopically CLH was seen as a slightly opaque curly mass in the anterior chamber in the eyes that otherwise were quiet in four of the rabbits. In one rabbit the injected cross‐linked substance reacted immediately with aqueous and turned white. The eye was quiet and showed no inflammatory signs. In all intracamerally injected eyes, slight to moderate aqueous flare was present 4 h post injection. Aqueous flare was still present 1 day post injection in 4 eyes, but was absent 4 days post injection. Histologically no apparent inflammatory reaction was present. Occasional giant cells were seen on the anterior surface of the iris in three animals. Slight accumulation of mononuclear cells was found in the iridocorneal angle of the CLH injected eyes. At histology few mononuclear cells were also found surrounding the subconjunctivally injected CLH still present in 4 additional rabbits when euthanatized 28, 42 and 49 days post injection. The contralateral eye of these 4 animals received an equal amount of sodium hyaluronate subconjunctivally. The substance had been resorbed completely. No reactive or inflammatory signs were present. In this study the cross‐linked hyaluronic acid caused moderate foreign body reaction in the structures of the anterior chamber and in the subconjunctival tissue of the rabbit eye. Further investigations are needed to show if hyperviscous substances possibly could be used in the prevention of scleral and subconjunctival adhesions in glaucoma surgery.