Novel View Of Dispersive And Cohesive Ophthalmic Viscosurgical Device Dynamics And Corneal Endothelium Protection During Simulated Phacoemulsification And Biochemical Oxidative Stress

The aim of this study was to 1) compare the dynamic behavior of a chondroitin sulfate-containing dispersive (Viscoat, Alcon) and a cohesive (Healon Pro, J&J) ophthalmic viscosurgical device (OVD) during simulated phacoemulsification for physical protection of the corneal endothelium using live, intraoperative optical coherence tomography (iOCT) videos in an ex vivo porcine eye model; and 2) compare the biochemical protective effects of these two OVDs on cultured rabbit corneal endothelial cells (CECs) in an in vitro oxidative stress model. Protecting the corneal endothelium during phacoemulsification is crucial, as damage to these non-regenerative CECs may lead to irreversible corneal edema and vision loss.

Experimental ex vivo bench study and in vitro cell culture study; Alcon Research LLC, Fort Worth, Texas, USA.

400μL of dispersive or cohesive OVD stained with contrast agent was injected into the anterior chamber (AC) of ex vivo porcine eyes (5 eyes/group). The Centurion phacoemulsification balanced tip was inserted into the AC above the crystalline lens; 60% torsional ultrasound with 38 cc/min flow, 50 mmHg intraocular pressure, and 550 mmHg vacuum was then applied for 45 seconds. OVD retention dynamics were recorded via iOCT videos, then analyzed using ImageJ. Cultured CECs in a 96-well plate were exposed to OVD or BSS control mixed with media containing hydrogen peroxide for oxidative stress for 2.5 hours at 35 °C (18 wells/group). The cell culture supernatant was quantified for lactate dehydrogenase (LDH) at 500 nm absorbance in a plate reader.

The iOCT videos showed real time OVD retention dynamics during simulated phacoemulsification and demonstrated an intact corneal endothelial protective layer with the dispersive OVD (>45 sec) in contrast to the cohesive OVD (2.3 sec ± 0.4 sec) (P=0.008, Fisher’s exact test). For the biochemical oxidative damage assay, the mean percentage of CEC damage was significantly lower for the dispersive OVD with chondroitin sulfate (34.8% ± 5.5%) compared to the cohesive OVD (60.3% ± 6.1%) and no OVD (BSS) control (100% ± 7.3%) (P=0.001, ANOVA).

Using iOCT, a novel method was developed to observe real-time, cross-sectional OVD dynamics in the AC during simulated phacoemulsification. With this new model, a chondroitin sulfate-containing dispersive OVD visually demonstrated sustained, physical corneal endothelial protection throughout phacoemulsification. In contrast, the cohesive OVD visually demonstrated a lack of corneal endothelial protection immediately at the start of phacoemulsification. Furthermore, the dispersive OVD had significantly increased CEC protection against oxidative stress compared to the cohesive OVD in an in vitro biochemical assay.