To evaluate the safety and efficacy of hydroxyapatite-magnesium (HA-Mg) glaucoma drainage plate after implantation in rabbit eyes.

Twelve New Zealand white rabbits were randomly assigned to HA-Mg drainage implant group and trabeculectomy group using the paired comparison method, with 6 rabbits in each group.The right eyes of rabbits were taken as the experimental eyes, and the left eyes of rabbits were taken as a normal control group.HA-Mg drainage implant group underwent implantation of the HA-Mg drainage plate and the trabeculectomy group underwent trabeculectomy.At 1, 3, and 5 months after surgery, the ocular condition was observed by slit-lamp examination with auxiliary lenses and the fixation of the drainage plate in the anterior chamber and subconjunctiva was measured by ultrasound biomicroscopy.At 5 months after surgery, corneal endothelial cell counts were performed with a corneal endothelial cell counter.The intraocular pressure (IOP) was continuously measured weekly for 21 weeks preoperatively and postoperatively.The flow patency of aqueous humor drainage channel was identified by the injection of trypan blue in anterior chamber.The aqueous humor drainage channels and surrounding tissues were evaluated by hematoxylin-eosin (HE) staining after HA-Mg drainage plate was completely degraded.This study was in accordance with China Animal Welfare Law and the ARVO Statement on the use of animals for ophthalmic research, and animal experiments were conducted in accordance with the Regulations on the Administration of Experimental Animals issued by the National Science Council.The study protocol was reviewed and approved by the Ethics Committee of The Third Affiliated Hospital of Chongqing Medical University (No.Kelun Pre-Examination [2021]14).

No systemic or ocular side effects were observed in the experimental animals after surgery.All 6 HA-Mg drainage plates were completely degraded about 4 months postoperatively, among which 4 plates were well-fixed and 2 plates had a minimal rotation, and no plate moved into the anterior chamber.At 5 months after surgery, the number of corneal endothelial cells in the HA-Mg drainage implant group and normal control group was 2 535.2±274.4 and 2 521.0±175.8, respectively, and there was no statistical significance between them (t=0.073, P=0.857).There were statistically significant differences in IOP among the three groups at different time points before and after surgery (F_group=26.409, P<0.001; F_time=7.843, P<0.001), in which the IOP in trabeculectomy group and normal control group at different time points after surgery was higher than that in HA-Mg drainage implant group, and the IOP in HA-Mg drainage implant group at different time points after surgery was lower than that before surgery (all at P<0.05).The patency test revealed that the trypan blue could still drain from the anterior chamber to the subconjunctiva 5 months after HA-Mg drainage plate implantation.The scleral linear aqueous humor drainage channel and anterior synechia were observed after drainage plate completely degraded 6 months postoperatively, and no obvious inflammatory cell infiltration was seen.

After implantation of HA-Mg drainage plate in rabbit eyes, the intraocular pressure can be effectively lowered and the safety is good.

Glaucoma; Glaucoma drainage device; Glaucoma external drainage surgery; Hydroxyapatite-magnesium