Comparison of the effects of various lubricant eye drops on the in vitro rabbit corneal healing and toxicity

Ingredients of lubricant eye drops are potentially harmful to the ocular surface. The products Optive, Optive Fusion, Neopt were tested regarding corneal irritability versus Vismed Multi and 0.01% benzalkonium chloride as negative and positive control, respectively. Formulas (30–40 μl per hour) were applied hourly in-vitro for six days on rabbit corneas (n = 5, per product) cultured in artificial anterior chambers (EVEIT system). Initially, four corneal abrasions (2.4–4.6 mm²) were induced. All defects were monitored during drop application by fluorescein stains and photographs. To ensure corneal vitality, glucose and lactate concentrations in artificial anterior chamber fluids were determined photometrically.

All products showed a complete corneal healing on day 2. Thereafter, all five Optive-treated corneas developed progressive fluorescein-positive epithelial lesions until day six (24.96 μm, ±21.45 μm, p < 0.01). For Optive Fusion three corneas showed corneal erosions on day six (23.11 μm, ±37.02 μm, p > 0.5) while Vismed Multi did not adversely affect the corneal integrity. Glucose/lactate concentrations remained unchanged while lubricants were applied. Histology revealed epithelial loss and severe alterations of the superficial stroma for Optive. Optive Fusion displayed a comparable pathology. Neopt did not significantly affect the corneal healing and integrity.

This study suggested a cumulative corneal toxicity of Optive and, to a lesser extent, Optive Fusion most likely caused by its oxidative preservative, SOC. Clinical data are needed to clarify the application frequency at which corneal toxicity might occur. Neopt and Vismed Multi did not affect the corneal integrity.