News reports from the conference

Preservative exposure tied to surgical failure

Using eye drops containing the common preservative - benzalkonium chloride (BAK) - is associated with a risk of early surgical failure following trabeculectomy, a University of Toronto study has confirmed.

Results from the Preservative Exposure and Surgical Outcomes in Glaucoma Patients (PESO) study were presented here by medical student Corey Boimer, who conducted the research with Sunnybrook Health Sciences Centre Associate Scientist Dr. Catherine Birt.

Boimer explained that BAK is a detergent that is found in most commonly used ophthalmic solutions and has been associated with surgical failure in the past.

In order to investigate this issue, the researchers conducted a retrospective chart review for 128 glaucoma patients who underwent trabeculectomy between 2004 and 2006 and for whom at least two years of follow-up data were available.

Complete surgical success was achieved in 47.7% of cases, and patients received between one and eight BAK-containing drops daily.

The study found that time to surgical failure in patients receiving higher preoperative daily doses of BAK was shorter than in those with less BAK exposure (p = 0.008). Boimer said that for each additional BAK-containing drop used daily, the hazard ratio for early surgical failure was 1.21. However, no association was seen between the number of different medications used to control intraocular pressure and time to surgical failure.

An ophthalmologist attending the session commented that the impact of BAK-containing eye drops is "an unresolved detective story" with the mechanism for potential toxicity still unclear.