Timing povidone prophylaxis

What you should knowabout prophylactic use ofpovidone-iodine

In one study, eye cultures were reduced from 87% to 30% after povidone-iodine use
Fewer species grew, and they grew in lighter concentration after povidone-iodine administration, the report noted.
Contact time of povidone-iodine is important; three minutes works well

Source: Zia I. Carrim, M.R.C.Ophth.

Two views of post-op endophthalmitis
Source: Nick Mamalis, M.D.

Although many ophthalmologists advocate the use of povidone-iodine before cataract surgery to prevent infection post-op, a new study offers unique insights into the efficacy of this prophylaxis.
Contact time of povidone-iodine with the ocular surface, for instance, may be an important factor.
“This is the first study specifically highlighting the importance of adequate contact time with povidone-iodine prior to intraocular surgery,” according to a report by Zia I. Carrim, M.R.C.Ophth., department of ophthalmology, St. James’s University Hospital, Leeds, England. “Use of 5% povidone-iodine for 3 minutes prior to cataract surgery achieves a significant reduction in organisms such as CoNS [Coagulase-negative Staphylococcus] from lid and conjunctival flora.”
The study, published in the July-August 2009 issue of the European Journal of Ophthalmology, is limited in that it did not vary contact time with respect to povidone-iodine on the ocular surface. It only analyzed three minutes of pre-op povidone-iodine use or no use at all. Dr. Carrim did, however, compare the study’s results with other previous studies with varying amounts of contact time (or no contact time cited).
The study found that contact time appears to be an essential factor concerning the use of povidone-iodine, and future studies—as well as practitioners—may want to take note.

An eye on time

Dr. Carrim and colleagues analyzed 54 patients that underwent unilateral cataract surgery. Five percent povidone-iodine was applied to the surgical eye for three minutes prior to surgery, while the other eye was the control.
Both eyes were swabbed for organisms before povidone-iodine application, as well as three minutes afterward.
Before povidone-iodine use, 87% of surgical eyes and 92% of control eyes had positive cultures—a statistically insignificant difference. The mean number of species between the groups was also not statistically significantly different.
A different story unfolded after povidone-iodine use. In surgical eyes, only 30% had positive cultures. Further, only CoNS was isolated after application. The growth of CoNS also was lighter than before application.
Culture-positive swabs, mean number of species, and growth of CoNS remained unchanged in the control group.

Results in context

While the study did not analyze the effect of povidone-iodine after other time points—such as two minutes or five minutes—Dr. Carrim determined (based on this study’s results, previous ophthalmic society recommendations, and literature reports) that use for three minutes seems to be just right.
“The present study specifically validates the ESCRS recommendation of 5% povidone-iodine for 3 minutes by demonstrating a significant reduction in culture-positive swabs … and mean number of species,” Dr. Carrim reported.
Some former research found that povidone-iodine helped reduce bug colonies but the research did not cite contact time. Other research studied the quantity of drops used, and although they did cite time, Dr. Carrim suggested that study variations make definitive comparisons impossible.
“[Some researchers] used one drop of 5% povidone-iodine for 2 minutes and observed a drop from 75% to 28% in the proportion of culture-positive swabs before and after preparation,” Dr. Carrim noted. “More recently, [other researchers] found that conjunctival irrigation using 10 mL of 5% povidone-iodine was associated with a lower proportion of positive cultures compared with using two drops of the same preparation (18% vs 32%). A contact time of approximately 5 minutes was stated and all patients also had preoperative ofloxacin.”
Some research has suggested that there is no difference between using povidone-iodine for three minutes versus two minutes.
“[Based on] a study with similar methodology, it is arguable that there appears to be no significant additional reduction in culture positivity of swabs from using povidone-iodinefor 3 minutes instead of 2 minutes (30% vs 28%),” Dr. Carrim noted. “Growth of isolates was not evaluated and it is possible that positive cultures after 3 minutes may have fewer CFUs [colony forming units] than after 2 minutes.”
Regardless of usage duration, John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., said povidone-iodine is critical in the prevention of endophthalmitis.
“I don’t think there’s any doubt that povidone-iodine is a key step in preventing operative infections,” Dr. Sheppard said. “It’s one step that I would comfortably apply to the category of community standard.”
Dr. Sheppard also suggested that while many surgeons use fluoroquinolones perioperatively—and have a lot of data to support such use—“even more powerful is the application of an iodine compound to prevent endophthalmitis,” he said.

Editors’ note: Dr. Carrim did not indicate any financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information

Carrim: zia.carrim@doctors.org.uk
Sheppard: 757-622-2200, docshep@hotmail.com