Liquid gel therapy broadens role of dry eye product line

May 1, 2006

Miami-The introduction of Systane Free Lubricant Eye Drops (Alcon Laboratories Inc.) has further diversified the company's product line to enable optimization of artificial tear treatment for the broad spectrum of patients suffering with dry eye, said Terrence P. O'Brien, MD.

Miami-The introduction of Systane Free Lubricant Eye Drops (Alcon Laboratories Inc.) has further diversified the company's product line to enable optimization of artificial tear treatment for the broad spectrum of patients suffering with dry eye, said Terrence P. O'Brien, MD.

The new product is a low viscosity, liquid gel formulation that also incorporates a unique self-preserving ionic buffer system. In contrast with the company's original Systane, it is formulated at a higher pH, dispenses as a thicker product, and uses a novel preservation system consisting of borate, sorbitol, aminomethyl propanol, and zinc, according to Alcon. Those four components create a hostile antimicrobial environment and prevent microbial growth in the multi-dose dropper bottle. However, on contact with electrolytes found in the tear film, the ionic buffer preserving system dissociates into its individual components, which are entirely non-toxic to epithelial cells.

The Systane product line offers the unique gel matrix technology that is based on cross-linking of borate and HP-Guar to form a meshwork able to retain the active demulcents, polyethylene glycol 400 and propylene glycol, on the ocular surface, according to Alcon. Since the company's new preservative-free product is formulated at a higher pH than its predecessors, there are limited ionic interactions between borate and HP-Guar in the bottle that lead to a pre-gelled state. More extensive cross-linking between borate and HP-Guar is promoted when the new preservative-free formulation comes into contact with the lower pH of the ocular surface.

"Systane Free liquid gel is a true gel in the bottle and on the eye where its polymer matrix acts almost like a liquid bandage contact lens, helping to restore the microenvironment of the ocular surface and facilitate recovery of the epithelial cells. However, not all ophthalmic gels are created equal," said Dr. O'Brien.

He explained that some products are labeled as "gels" because of their thicker consistency. However, they achieve increased viscosity by incorporating a higher concentration of polymer.

"Once the product comes into contact with the eye, it is rapidly diluted by the tear film, but not before causing some blurring and eventually causing crusting as excess product washes out onto the lashes," he explained.

Other true gel formulations exist, but the polymer network in those agents collapses quickly when instilled onto the eye. Compared with those products, Systane Free exists as a gel matrix on the eye to provide superior protection that can be quantified by objective improvement in corneal staining and subjective relief of patient symptoms, Dr. O'Brien said.

"Recent advances in dry eye research have led to the understanding that [similar to] glaucoma, the diagnosis of dry eye does not describe a single condition but rather a number of different disorders that result in a dysfunctional tear state. Importantly, the term 'dry eye' is an inadequate descriptor since the condition is characterized by deficiencies in both tear film quality as well as quantity. With that recognition in mind, the Systane product line is particularly effective as artificial tear treatment because its unique formulation addresses the problems with tear film functionality," Dr. O'Brien said.

Matching patient needs

Another hallmark feature of dry eye is that its severity ranges widely across the affected population. However, physicians may underestimate the magnitude of the problem if they base their assessments primarily on clinical signs.

"There can be a disconnect between the severity of the findings from the ocular examination and the patient's symptoms, and it is important in the diagnostic evaluation to determine what impact the dysfunctional tear state has on the patient's quality of vision and quality of life," Dr. O'Brien said.