Eye drops for contact lens wearers are found to be safe

Key Points

Louisville, KY-Ever since soft contact lenses were introduced in the United States in 1971, eye care practitioners have been searching for new procedures or products that help minimize dry eye for their patients who wear contact lenses and who typically make up a large percentage of their practice. Recent studies show that an estimated 17 million lens wearers are significantly affected by dry eye. Worse yet, many drop out of contact lens wear because of dryness.

So last year, Ian Benjamin "Ben" Gaddie, OD, FAAO, an optometrist at Gaddie Eye Centers in Louisville, KY, and Jodi Luchs, MD, FACS, an ophthalmologist at South Shore Eye Care in Wantagh, NY, jointly conducted a clinical trial at their respective centers that tested the safety and efficacy of a proprietary lubricating eye drop (Optive, Allergan) in contact lens wearers. The over-the-counter eye drop offers an advanced dual-action formula designed to lubricate and hydrate dry eyes. At the end of the study, participants reported no adverse events and that their lenses were more comfortable.

Dr. Gaddie presented the study's results. The 4-week trial was conducted in January 2008. Thirty-six patients-roughly half from each location-were chosen for the study. The selection criteria included: self-reported use of daily-wear contact lenses that had a proper fit for at least 1 month before the screening visit, patient discomfort due to dry eye while wearing lenses, and patients could not be taking any dry eye medications or use oral or topical antihistamines, which cause dryness, during the study, Dr. Gaddie said. Patients who used disposable lenses also were permitted to change their lenses according to their prescribed schedule.

Patients were required to insert two drops of the solution into their eyes each day during those 4 weeks to see whether it improved their wearing time and overall comfort with contact lenses.

Dr. Gaddie explained that patients were evaluated during the first, second, and fourth week for the following:

"This was really a basic study," he said. "We were looking to see if [the drops were] an appropriate formulation to use with contact lenses, if [they were] safe, and if [they] helped patients with their wearing time."

Outcomes and surprises

After 4 weeks of treatment, no adverse events or complications were reported by patients or found by the study's investigators. With each follow-up visit, patient comfort steadily increased. The mean OSDI score improved to 22.4 ± 15.7.

"A change of this magnitude suggests improvement in dry eye severity from moderate to mild symptoms," said Dr. Gaddie at the study's conclusion.

But what was even more surprising was that 100% of the participants reported that their lenses were comfortable.

"I didn't expect to see unanimous improvement among all participants enrolled in the study, especially given the multifactorial nature of dry eye," he said.

Dr. Gaddie noted several reasons why this could have occurred. Some eye drops on the market have a high viscosity level, meaning the drops are thick, so they can have long contact time with the eye. The stronger the viscosity, however, the more blurry a patient's vision, he said, adding that when wearing contact lenses, the blurring effect is even greater.

Although the test drops are noticeably thicker than some artificial tears, they are not as thick as some gel products, and the viscosity dissipates quickly with blinking. According to the study, although the enhanced viscosity is designed to increase the retention on the ocular surface, it also extends the drops' lubricating and moisturizing benefits.

The drops' ingredients also make a big difference, Dr. Gaddie said. Based on the study's report, one of the components is carboxymethylcellulose, which is an effective lubricant that prevents water loss on the surface of epithelial cells. The drops also contain glycerin, an osmoprotectant that restores the loss of cellular volume without increasing viscosity, and a gentle preservative (Purite) that doesn't damage the ocular surface. Likewise, erythritol and L-carnitine, which are small, nonionic organic compounds, also help build osmotic strength intracellularly without damaging the cell.

He added that the drops' compatible solutes also help buffer osmolarity and mesh with the eyes and natural tear contents. Considering all of these factors, Dr. Gaddie said he isn't really surprised that the drops would yield different results from other artificial tear preparations, which contain different lubrication properties.

In the future, different manufacturers of artificial tear agents may extend their line to include a version for contact lens "re-wetters." Meanwhile, patients typically purchase the least expensive drops, which tend to have higher viscosity and more preservatives. When used frequently over time, fluorescein staining also can occur.

But with this study and others, perhaps more eye care providers can educate their patients about which eye drops are clinically proven to be the most effective for contact lens wearers, Dr. Gaddie concluded.