Tear film rebuilding is goal of drop

Key Points

"[The drop] was created with a unique intelligent delivery system, and I think of this product as providing dynamic rebuilding of the tear film that can be distinguished from the performance of other artificial tear products," said Dr. Chuck, the Clancy Professor of Ophthalmology, Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore.

"Whereas other artificial tear products become diluted and washed out of the eye by lid-blinking and the natural tears, the cross-linked polymer network that is the foundation technology of [this drop] strengthens and becomes more elastic in the eye," he said. "The resultant structured network provides enhanced ocular surface protection and responds to the shear forces of the blinking lid so that comfort and vision clarity are maintained."

As does another drop in the same product family (Systane, Alcon Laboratories), the new drop delivers a polymer network formed by crosslinking of borate and hydroxypropyl (HP)-guar that adheres to damaged epithelium and retains the active demulcent ingredients, polyethylene glycol 400 and propylene glycol, on the eye. The new drop also contains sorbitol, which competes with HP-guar for bonding to borate so that the polymer network in the bottle is only loosely cross-linked and is more like a solution in consistency than a gel.

"Exposure to shear forces, both as the drop [of the new formulation] is squeezed through the bottle tip and then with the first eyelid blink, further reduces the viscosity of [the new formulation] so that the drop spreads readily over the eye and causes minimal blur," said Dr. Chuck.

After instillation, the sorbitol in the new drop is diluted by the tear film, allowing greater interaction between borate and HP-guar, and this cross-linking is further promoted by divalent ions in the tears, magnesium and calcium, he said. The resultant more extensive polymer network also has enhanced elasticity, Dr. Chuck added.

"[The new drop] has been engineered to provide the benefits of a gel on the eye but without the vision-disturbing blur that can accompany these thicker formulations," he said.

Laboratory model

In a laboratory model, the new formulation has been shown to have a greater benefit than other artificial tears for decreasing the coefficient of friction between tissues, a measure of lubricating activity, Dr. Chuck said. Although no clinical studies have been published demonstrating the efficacy and safety of the new drop for the treatment of dry eye disease, its on-eye physicochemical characteristics have been established in laboratory bench models, he added. In addition, because the new formulation contains the same demulcents and polymer components as its sister formulation, it can be expected to provide the same benefits to patients, but perhaps to a greater extent and for a longer period of time, Dr. Chuck said.

"Because [the new drop] is new, confirmational, controlled clinical trial studies still need to be done to confirm these anecdotal impressions," he said.