Suprachoroidal Injection Of Cross-linked Hyaluronic Acid As An Internal Buckling Procedure In Rabbit Eye

ObjectiveBased on scleral buckles and the concept of minimally invasive surgery, this study was designed to investigate efficiency and feasibility of internal buckling with suprachoroidal injection of cross-linked hyaluronic acid (CLHA), to evaluate the safety of the surgical procedure and the CLHA as an implant in suprachoroidal space and try to find a different way to treat the retinal detachment (RD) and myopic traction maculopathy (MEM).Methods27 healthy adult black rabbits were included in this study and were randomly divided into 3 groups. In group A (n=12), CLHA was injected into suprachoroidal space and in group B (n=12), HA was injected into suprachoroidal space. Group C (n=3) as a normal control group which didn’t perform any treatment. Preoperative examinations were performed to exclude any eye disorders. Under microscope a trapezoid flap was made in conjunctiva with a base on fornix supranasally or supratemporally, then a 3-mm full-thickness scleral incision was performed which was parallel and 5 mm from the limbus. Choroid and sclera were separated with a 27g microcatheter. Then 0.1-0.15ml CLHA or HA was injected into target space through a 27g silicon microcatheter. This procedure was monitered with indirect ophthalmoscopy. The scleral and conjunctival incisions were sutured with 7-0 vicryl Sutures. Fundus examination with direct ophthalmoscopy, fundus photography, intraocular pressure (IOP), and B-mode ultrasound were performed before and 1,2,3 days and 1,2,4,8 weeks after injection. Scotopic-adapted electroretinography (ERG) was performed at baseline,1w,4w,8w after injection. Histopathological examinations were performed at 4w and 8 w postoperatively.Results1. Fundus examination After injection, there was visible elevation of the retina and choroid as an internal buckling, which was dome-shape, well-defined and about 5-7 papillary diameters. The buckle volume of the experimental eyes in both A and B group kept decreasing slowly during follow up.The decrease was more rapidly in group B than in group A. In group A, suprachoroidal buckling was confined to its original during follow up.The height as well as area of choroidal elevation decreased very slowly and there was no spread of CLHA.The elevation was only kept for the first 12-72 hs in group B.2. Complications Duration of the surgical procedure was less than one hour In all the experimental eyes.32 cases have been performed the surgery and The operative complications mainly included:choroidal hemorrhage (1/32),vitreous loss (3/32), choroidal tear and retinal tear (3/32), endophthalmitis (1/32). Flake bleeding under choroid occurred in 1 case postoperatively and absorbed in 1 week. Conjunctivitis happened in 6 cases after surgery and recovered during 1 week.3. Intraocular pressure At every time point (1h, Id,2d,3d, 1w,2w,4w,8w after injection), paired t test was conducted for the comparison of the intraocular pressure (IOP) between the surgery eye and the control eye in both A group and B group and statistic analysis of IOP in A group, B group and C group was conducted using analysis of variance.There was no significant difference in IOP between surgery eye and control eye (P>0.05) and no significant difference in postoperative IOP among three groups (P>0.05).4. Ultrasonography On B-scan dome-shaped, well-defined choroid detachment could be found, the echo in the detachment area is similar to that in the vitreous cavity. The hypoechogenic area in suprachoroidal space kept at least for 8 weeks but the volune kept decreasing gradually in goup A. Choroid detachment in the same style could be found in the experiment eyes in group B, but it is more flat and not so well-defined compared to that in group A, furthermore the height and extent decreased rapidly in 3 days and disappeared completely in lweek postoperatively.5. F-ERG The dark adaption F-ERG data was analyzed by paired t test,at four timepoints (baseline,1,4,8 weeks after injection). There was no significant differences in latency of amplitudes of the ERG wave among the three groups (P >0.05).6. Histological examination Four weeks after injection. In group A it was showed Choroid were indented by CLHA to vitreous cavity and the suprachoroidal space was filled with homogeneous red dyed material, A few inflammatory cells and phagocytes could be observed. In group B it was revealed choroid and retina appeared intact without choroid detachment 4 weeks after surgery.8 weeks after suprachoroidal CLHA injection, suprachoroidal space was still filled with CLHA, but both the amount of CLHA and inflammatory cells were decreased. Except for that mentioned above, there was pigmentation disorder and vacuoles in choroid.Conclusions1. In this study, CLHA injected into the suprachoroidal space of rabbit eyes with silicon microcatheter via full-thickness scleral incision created a choroid-only (without sclera) buckle, which could support the retina. B-scan ultrasonography, F-ERG and histological examination proved that internal buckling was effective, long-lived and safe.2. CLHA was a proper material for suprachoroidal buckling implantation.3. Suprachoroidal space was a potential space, which was considered one of the best places to implant internal buckling graft.