Biotrue and two other solutions with similar polyhexamethylene biguanide formulations did not alter corneal barrier function as compared with balanced salt solution and phosphate buffered saline controls.
"Since MPSs are routinely inserted into the eye, it is important that they are fully biocompatible with the ocular surface. The corneal epithelium is the first layer of contact on the ocular surface. By performing in-vitro assays on these monolayers, assessments can be performed on whether MPSs are having an effect on the epithelium," said Harrington, of Bausch + Lomb.
To study the effects of the five commercially available MPSs, investigators analyzed epithelial barrier function by using two in-vitro assays. Monolayer integrity (scanning electron microscopy) was used to monitor ultrastructural alterations, and monolayer resistance (electric cell-substrate impedance sensing [ECSIS]) was used to perform a real-time, noninvasive, highly sensitive assay.
Electric cell-substrate impedance testing revealed that the epithelial cells exposed to only 50% levels of Opti-Free Express and Opti-Free Replenish (Alcon) were different from all groups after 20 minutes, while cells exposed to the other three solutions, Biotrue, AQuify (CIBA Vision), and Complete Multipurpose Solution Easy Rub (AMO), were not significantly different from media and PBS control at any time.
"It is likely that a combination of excipients in the lens care solutions-antimicrobial agents, buffering agents, surfactants and chelating agents-are the causative factors in the adverse effects seen with using Opti-Free Express and Opti-Free Replenish on the corneal epithelial cells," said Dr. Merchea, who is director, medical affairs, Bausch + Lomb. "These in-vitro assays may be a valuable indicator of the eventual clinical observations or trends in determining MPS and contact lens biocompatibility."