A new histological evaluation method to detect residual ophthalmic viscosurgical devices for cataract surgery

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

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.

Advances in Understanding the Mechanism of Ophthalmic Viscosurgical Device Retention in the Anterior Chamber or on the Corneal Surface during Ocular Surgery

Retention durability, especially in the eye, is one of the most important properties of ophthalmic viscosurgical devices (OVDs) during ocular surgery. However, the information on the physical properties of OVDs is insufficient to explain their retention durability. The purpose of this study is to clarify the mechanism of OVD retention to improve understanding of the behavior of OVDs during ocular surgery. To elucidate the mechanism of OVD retention, we have developed a new test method for measuring repulsive force. As a result, the maximum repulsive force of OVDs was positively and well correlated with the retention durability of investigated OVDs. Consequently, we demonstrated that the repulsive force could be used as an index of retention durability on the ocular surface and in the eye. We directly compared the intraocular retention durability of three OVDs (Shellgan, Viscoat, and Opegan-Hi) in ex vivo porcine eyes. Opegan-Hi was immediately removed from the anterior chamber, but Shellgan and Viscoat remained largely in the anterior chamber as determined by fluorescence imaging. These results showed that the intraocular retention behavior of OVDs was similar to their ocular surface behavior in our previous report, suggesting that retention durability is dependent on the OVD itself. The retention durability of Shellgan seemed to be higher than that of Viscoat, and the maximum repulsive force of Shellgan was 1.35-fold higher than that of Viscoat. Therefore, the repulsive force might be a useful index for assessing the difference in the retention durability between OVDs such as Shellgan and Viscoat.