Thickness of the Protective Layers of Different Ophthalmic Viscosurgical Devices During Lens Surgery in a Porcine Model

Abstract

Purpose To evaluate the thickness of the intraoperative layers of 10 different ophthalmic viscosurgical devices (OVD) covering the corneal endothelium during simulated lens surgery in a porcine model. Methods This experimental study took place at the Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria. Ten OVDs with different viscoelastic properties (ProVisc, Z-Hyalin plus, Amvisc plus, DisCoVisc, Healon EndoCoat, Viscoat, Z-Hyalcoat, Combivisc, Duo-Visc, and Twinvisc) were assessed in 10 porcine eyes each, yielding a total of 100 eyes. Simulated cataract surgery was performed with volumetric intraoperative OCT imaging during phacoemulsification and during irrigation/aspiration to determine the remaining amount of OVD coating the endothelium over a scan field of 6 × 6 mm. Indirect visualization of the OVD was enabled by replacing the irrigating solution by a higher scattering diluted milk solution. A deep convolutional neural network (CNN) was used to evaluate OVD layer thickness based on the B-scans. Results Median thickness values after phacoemulsification were lowest for the cohesive OVDs Z-Hyalin plus (38 µm) and ProVisc (39 µm), followed by the combination systems Twinvisc (342 µm) and Duo-Visc (537 µm). Highest values were observed for the dispersive OVDs and the combination system Combivisc (Viscoat: 957 µm; Z-Hyalcoat: 988 µm, Combivisc: 1042 µm; Amvisc plus: 1259 µm; Healon EndoCoat: 1303 µm; DisCoVisc: 1356 µm). The difference between the OVDs was statistically significant ( P < 0.01). Conclusions The results of this study confirm that at completion of phacoemulsification, thickest residual layers of OVD remain when using dispersive substances, followed by combination systems and lowest thickness values were observed with cohesive OVDs. The use of an intraoperative OCT and a deep convolutional neural network allowed measurements over a large scan field of 6 × 6 mm and a precise evaluation of the OVD layer coating the corneal endothelium. The OVD layer seemed to be more like a ragged terrain instead of a flat layer, indicating that the film-forming effect of dispersive OVDs is the result of their volume rheology rather than a surface interaction. Translational Relevance Evaluating the protective properties provides valuable insights into how different OVDs with different viscoelastic properties form layers beneath the corneal endothelium and helps to understand their persistence during the various steps of cataract surgeries.

Visualization of Cataract Surgery Steps With 4D Microscope-Integrated Swept-Source Optical Coherence Tomography in Ex Vivo Porcine Eyes

“…Another useful example may be the monitoring of the OVD protection layer thickness to warn the surgeon of potential damage to the corneal endothelium. 32 The full eye volume capture scans shown in this work cover large FOVs and can be rendered and displayed intraoperatively after only few seconds of processing time. Such scans can be used to check the orientation and position of the IOL (e.g., centration) and tilt in the capsular bag intraoperatively, which may be important for the surgical outcome.…”

Temperature-controlled porcine eye holder for observing intraocular temperature during cataract surgery

“…Enucleated porcine eyes have been used in the ex vivo evaluation of the performance and effects of phacoemulsification and aspiration (PEA) 1,2 , femtosecond laser-assisted cataract surgery 3,4 , ophthalmic viscosurgical devices (OVDs) [5][6][7] , and implantation of intraocular lens (IOL) 8,9 . Porcine eyes are usually preserved at low temperatures, whereas balanced salt solution (BSS) and OVDs used in the ex vivo experiments are stored at lower temperatures in the surgery room or laboratory, such as 20-25 °C or 68-77 degrees Fahrenheit.…”