A Shape Memory Polymeric Shield for Protecting Corneal Endothelium During Phacoemulsification

Abstract

Background: The purpose of this study was to explore the protective effect of a shape memory polymeric shield on corneal endothelium during phacoemulsification in rabbits.

Methods: Poly-(glycerol dodecanedioate) (PGD) with a transition temperature of 24.416°C was prepared to make a shape memory shield with a thickness of 100 µm, an arc length of 14 mm, and a radius of curvature of 8.8 mm. In the control group, a phaco-tip with bevel-down was used to simulate injury to the corneal endothelium by phacoemulsification in rabbits. In the experimental group, the pre-cooled and curled shape memory shield was injected into and removed from the anterior chamber before and after phaco-power release. Anterior segment optical coherence tomography (AS-OCT), confocal microscope, trypan blue/alizarin red staining, and scanning electron microscope were performed to measure endothelial damage after surgery.

Results: One day postoperatively, the lost cell ratio of the control group and the experimental group were 28.08 ± 5.21% and 3.50 ± 1.43%, respectively (P < 0.0001), the damaged cell ratios were 11.83 ± 2.30% and 2.55 ± 0.52%, respectively (P < 0.0001), and the central corneal thicknesses (CCT) were 406.75 ± 16.74 µm and 340. 5 ±13.48 µm, respectively (P < 0.0001). Seven days postoperatively, the endothelial cell density (ECD) of the control group and the experimental group were 1674 ± 285/mm2 and 2561 ± 554/mm2, respectively (P < 0.05). The above differences were all statistically significant.

Conclusions: This PGD based shape memory shield has a protective effect on corneal endothelium during phacoemulsification. It reduces postoperative corneal edema and ECD decrease in the short term after surgery.

Translational relevance: The shape memory PGD "shield" in this study may have a use in certain human patients with vulnerable corneas of low endothelial cell count or shallow anterior chambers.

Figure 1.

Surgical procedure of the experimental group. (a) A 3 mm corneoscleral incision was made and OVDs were injected into the anterior chamber; (b) the precooled highly curled “shape memory shield” was implanted into the anterior chamber through the incision; (c) the location of the “shield” in the anterior chamber shown by an AS-OCT; (d) a phaco-tip was located in the pupil center on the iris plane and released phaco-power; (e) after the injection of the OVDs, the “shield” was removed from the anterior chamber through the incision; and (f) the OVDs was replaced by infusion fluid and the incision closed spontaneously.

Figure 2.

Sketch showing the five endothelial areas selected in each sample. The dotted line represents the radial cut at the 12 o'clock position.

Figure 3.

Tests of the PGD material. (a) Fourier transform infrared spectroscopy (FTIR) analysis. (b) Transition temperature. (c) CCK8 test. (d) Light transmittance.

Figure 4.

Image study results. (a) Anterior segment photography; (b) AS-OCT; (c) confocal microscopy; (d) CCT measured by AS-OCT of both groups; and (e) ECD measured by confocal microscopy of both groups. (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Figure 5.

SEM (a) and trypan blue/alizarin red staining (b) results. (c) Cell loss ratio (red staining). (d) Cell damage ratio (blue staining; *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Figure 6.

Geographic shape design of the “shape memory shield” according to the parameters of the rabbit cornea and anterior chamber.