Efficacy of artificial tears tested under arid conditions

Key Points

An efficacy evaluation comparing two marketed artificial tears showed that a polyethylene glycol/propylene glycol (PEG/PG)-based product (Systane Ultra, Alcon Laboratories) resulted in statistically significantly greater reductions in corneal and conjunctival staining than a glycerin/carboxymethylcellulose (CMC)-based tear (Refresh Optive, Allergan).

The six-week study compared the two artificial tears under arid environmental conditions; the glycerin/CMC-based tear was used as the control.

The PEG/PG-based tear also showed a greater change from baseline in conjunctival staining than the glycerin/CMC-based tear. Symptom reduction from baseline was significant and occurred at a similar rate for both drops, according to results of the Treatment Satisfaction Questionnaire, the Ocular Surface Disease Index, and the VF-14 Questionnaire. The study was described in a poster presented by Mike T. Christensen, OD, PhD, of Fort Worth, TX, and colleagues at the 2009 annual meeting of the Association for Research in Vision and Ophthalmology.

The difference in corneal staining mean score favoring the PEG/PG-based tear was found overall (p = 0.0172) and at day 14 (p = 0.0009) and day 42 (p = 0.0106). In addition, a significant difference in conjunctival staining favoring the PEG/PG-based tear was observed overall (p = 0.0268) as well as at day 28 (p = 0.0475) and day 42 (p = 0.0009). Tear film break-up time was the same for both drops, averaging 4.5 seconds.

The double-masked, randomized, parallel study had an enrollment of 105 patients who had a =3 sum of corneal stain using the NEI grid (5 regions; max = 15 pts.) and a history of using artificial tears.

The subjects used a saline drop q.i.d. for 2 weeks before randomization. After the run-in period, they were instructed to use the test or control product q.i.d. for the duration of the study. Corneal and conjunctival staining were evaluated at each visit. No adverse events related to treatment were noted for either product.

The efficacy of the PEG/PG-based tear, like its predecessor (Systane), comes from its unique formulation, Dr. Christensen said. One component, hydroxypropyl-guar, provides a gelling effect which helps hold the demulcents, PEG and PG, longer on the surface of the eye. This provides prolonged protection and allows the ocular surface to heal.

In addition, the PEG/PG-based tear differs from the original formulation in that it is stored in the bottle at a pH of 7.9 versus 7, which more closely matches the pH of patients with more severe dry eye.

Dr. Christensen added that the PEG/PG-based tear is very comfortable, which likely aids compliance.

Functional vision

The functional visual performance of the PEG/PG-based tear and the glycerin/CMC-based tear also was evaluated in a separate study ("Functional visual performance on intensive tasks found better with artificial tear product," Ophthalmology Times, July 15, 2009).

Using the interblink interval visual acuity decay method, investigators demonstrated that the PEG/PG-based tear resulted in a statistically significant increase in the length of time within one line of best-corrected visual acuity (BCVA) within an interblink period at 90 minutes after instillation of a single drop.

Median times to one-line loss of BCVA were not statistically different at the timepoints of 15 or 45 minutes post-instillation.

FYI

Mike T. Christensen, OD, PhD
Phone: 817/551-8430
E-mail: mike.christensen@alconlabs.com

Dr. Christensen is an employee of Alcon Laboratories.