The effect of polyvinylpyrrolidone-iodine as an disinfectant in eye surgery

A randomised trial of povidone-iodine to reduce visual impairment from corneal ulcers in rural Nepal

AIM

To assess whether povidone-iodine provided any benefit over and above a standard regimen of antibiotic therapy for the treatment of corneal ulcers.

METHODS

All patients diagnosed with corneal ulcers presenting for care at a primary eye care clinic in rural Nepal were randomised to a standard protocol of antibiotic therapy versus standard therapy plus 2.5% povidone-iodine every 2 hours for 2 weeks. The main outcomes were corrected visual acuity and presence, size, and position of corneal scarring in the affected eye at 2-4 months following treatment initiation.

RESULTS

358 patients were randomised and 81% were examined at follow up. The two groups were comparable before treatment. At follow up, 3.9% in the standard therapy and 6.9% in the povidone-iodine group had corrected visual acuity worse than 20/400 (relative risk (RR) 1.77, 95% confidence interval (CI) 0.62 to 5.03). 9.4% in the standard therapy and 13.1% in the povidone-iodine group had corrected visual acuity worse than 20/60 (RR 1.39, 95% CI 0.71 to 2.77), and 17.0% and 18.8% had scars in the visual axis in each of these groups, respectively (RR 1.11, 95% CI 0.67 to 1.82).

CONCLUSIONS

A small proportion of patients with corneal ulceration treated in this setting had poor visual outcomes. The addition of povidone-iodine to standard antibiotic therapy did not improve visual outcomes, although this design was unable to assess whether povidone-iodine on its own would have resulted in comparable visual outcomes to that of standard therapy.

The effect of povidone iodine on the corneal endothelium

PURPOSE

Povidone iodine has been proven to be a valuable antiseptic solution in preparing the eye for surgery and is an alternative to postoperative topical antibiotics. No study has addressed the intraocular toxicity of povidone iodine after injection into the anterior chamber. We investigated the potential toxicity of povidone iodine on the corneal endothelium after injections into the anterior chamber in a rabbit model.

METHODS

In this study we used 24 eyes of 12 albino rabbits. The eyes were divided into the following three groups according to the drugs tested: group A, 5% povidone iodine; group B, 10% povidone iodine; group C, balanced salt solution. The injected eyes were evaluated by biomicroscopy, specular microscopy, corneal pachymetry, and transmission and scanning electron microscopy.

RESULTS

Corneal edema was observed in all eyes of groups A and B. In groups A and C, the endothelial cell morphology was not significantly changed and the mean endothelial cell count of the eyes did not change significantly (p = 0.5054). There was no significant difference in corneal thickness between groups A and C (p = 0.3823), but there was a significant difference between groups B and C ( = 0.0002). Transmission and scanning electron microscopy results were normal in group C but not in groups A and B.

CONCLUSION

Povidone iodine in both 5% and 10% concentrations demonstrates severe toxicity when one drop of either concentration is placed directly in the anterior chamber. When povidone iodine is used in preparing the eye for intraocular surgery and as an alternative to postoperative antibiotics, the inadvertent leakage of povidone iodine into the anterior chamber must definitely be prevented.

The effect of intracameral, per-operative antibiotics on microbial contamination of anterior chamber aspirates during phacoemulsification

PURPOSE

To assess the effect of per-operative antibiotics on contamination of anterior chamber (AC) aspirates during phacoemulsification.

METHODS

Two hundred and twenty patients undergoing phacoemulsification of cataract were randomly allocated to receive an irrigation infusion fluid containing either balanced salt solution (BSS) alone or BSS with vancomycin (20 mg/l) and gentamicin (8 mg/l) during surgery. Conjunctival swabs were obtained from all patients immediately before pre-operative preparation. At the end of surgery 20 ml of the AC aspirate was sent for direct and enrichment cultures. Qualitative and quantitative microbiological studies were undertaken. The chi-squared test was used to compare differences between the two groups.

RESULTS

There was no significant difference between the positive culture rates of the conjunctival swabs (28 vs 27; p > 0.8). In the group that received BSS alone there were 22 (20%) positive AC aspirate cultures, 18 of which were from enrichment cultures. There were 3 positive (2.7%) cultures from the group that received antibiotics added to the BSS (p < 0.0001).

CONCLUSION

The addition of gentamicin and vancomycin to the irrigation fluid during phacoemulsification results in a highly significant reduction in the microbial contamination of AC aspirates.

Effects of povidone-iodine chemical preparation and saline irrigation on the perilimbal flora

PURPOSE

To analyze the effects of 5% povidone-iodine preparation and saline irrigation on the species composition of perilimbal flora.

METHODS

Cultures were taken from the perilimbal conjunctiva in 100 eyes before preparation for ophthalmic surgery, after instillation of povidone-iodine solution, and after saline irrigation.

RESULTS

Bacteria were isolated in 75% of eyes before preparation, in 28% after povidone-iodine instillation, and in 24% after saline irrigation. Fifty-one culture-positive eyes became negative with povidone-iodine, while only four culture-negative eyes became culture-positive (P < 0.001). The number of eyes yielding coagulase-negative staphylococci, Staphylococcus aureus, and Propionibacterium were significantly decreased after povidone-iodine instillation. Twenty-three culture-positive eyes became negative after saline irrigation, while 19 culture-negative eyes became culture-positive (P > 0.25).

CONCLUSION

Povidone-iodine solution is effective in reducing bacterial recovery from the perilimbal conjunctiva, where most incisions for intraocular surgery occur. Saline irrigation after povidone-iodine preparation has no significant effect.

Prophylaxis of endophthalmitis with topical povidone-iodine

The authors conducted an open-label nonrandomized parallel trial to examine whether the preoperative application of povidone-iodine to the ocular surface reduces the incidence of endophthalmitis after intraocular surgery. During an 11-month period, topical 5% povidone-iodine was used to prepare the conjunctiva in 1 set of 5 operating rooms, while silver protein solution was used in another set of 5 rooms. In all cases, surgeons continued to use their customary prophylactic antibiotics. A significantly lower incidence of culture-positive endophthalmitis (P less than 0.03) was observed in the operating rooms using povidone-iodine (2 of 3489 or 0.06%) compared with those using silver protein solution (11 of 4594 or 0.24%). Use of topical povidone-iodine in over 3000 cases was not associated with any adverse reactions. In a majority of the observed cases of endophthalmitis, some form of intraoperative communication with the vitreous cavity existed.

Tolerance of intravitreal povidone-iodine in rabbit eyes

Povidone-iodine is frequently instilled on to the conjunctival surface prior to intraocular surgery in order to prevent septic endophthalmitis. A small amount of povidone-iodine is inevitably introduced into the eye when it is used in this manner. The toxicity of intravitreal povidone-iodine was assessed in rabbit eyes by injecting 0.1 ml of povidone-iodine in concentrations of 0.05%, 0.5% and 5% into the vitreous cavity. The injected eyes were evaluated by clinical examination, anterior segment and fundus photography, endothelial cell counts, electroretinography and histopathology. Compared to control eyes, no changes were observed in all 6 eyes injected with 0.1 ml of 0.05% povidone-iodine solution. 9 of 10 eyes tolerated a concentration of 0.5% with no detectable adverse changes. One eye developed a temporary mild iritis and mild suppression of the ERG. Intra-retinal hemorrhages, edema, arteriolar narrowing and retinal edema were seen one week following injection. Mild retinal necrosis of the same area was seen on histology. All 4 eyes injected with 5% povidone-iodine developed temporary hypotony and iridocyclitis. A dense cataract developed in all eyes. Full thickness retinal necrosis and a profound lasting reduction in the ERG was produced in all of these eyes. No corneal epithelial or endothelial changes were observed in any eye in this series. Low concentrations of intravitreal povidone-iodine likely to be produced by instillation prior to surgery are tolerated by rabbit eyes. The concentrations tolerated by the studied eyes are near reported bactericidal levels.

Outpatient topical use of povidone-iodine in preparing the eye for surgery

Povidone-iodine 5% solution placed on the eye immediately before ophthalmic surgery within the preoperative preparation significantly reduces the conjunctival bacterial flora. In 40 patients undergoing ophthalmic surgery, the authors compared the outpatient use of povidone-iodine for 3 days before surgery with a 3-day course of a combination antibiotic ophthalmic solution (Neosporin) placed on the other eye. All patients also received topical povidone-iodine on the operating table directly preceding surgery. Cultures taken just before preparation of the operative field showed a similar reduction of bacteria by each regimen. Cultures taken after preparation but before commencement of surgery showed a further reduction for both regimens, but more for eyes previously treated with the antibiotic (P less than 0.02). To minimize the conjunctival bacterial flora before surgery, the authors continue to recommend instillation of a broad-spectrum antibiotic for 3 days before surgery, followed by application of povidone-iodine solution to the eye immediately before surgery within the preoperative preparation.

Polyvinylpyrrolidone iodine: corneal toxicology and epithelial healing in a rabbit model

Polyvinylpyrrolidone-iodine (PVP-I) is a biocompatible broad spectrum antimicrobial that is widely used as an ophthalmic pre-operative prepping agent. In order to determine if PVP-I is safe for treating corneal ulcers and conjunctivitis, we evaluated the ocular toxicity of frequent dosing in a rabbit model. We evaluated ocular irritation in 18 rabbits according to the McDonald-Shadduck method. Concentrations of 0.5% PVP-I or less were practically non-irritating when administered six times per day. We evaluated corneal epithelial wound healing in 16 rabbits with standardized abrasions. Concentrations of 0.33% PVP-I showed epithelial healing comparable to gentamicin treated eyes and untreated controls. Concentrations of 0.5% PVP-I delayed epithelial healing by one day. Because of its broad spectrum and apparently low toxicity, PVP-I may be a useful treatment for corneal ulcers, keratitis and conjunctivitis.

Polyvinylpyrrolidone-iodine as a disinfectant in eye surgery for five years

Polyvinylpyrrolidone-iodine is a broad spectrum disinfectant which has been used in surgery for several years. The prophylactic effect of PVP-iodine against panophthalmia was examined in a study including all cataract operated eyes (4111 eyes) from autumn 1981 to the end of 1986. The patients were randomly split up into two groups. Group 1 received PVP-iodine eye-drops as a pre-operative disinfectant, the control group received 2.5% iodine on the skin only. Thirty-two cases of panophthalmia arose, 0.8% in group 1 (21 out of 2550 eyes) treated with PVP-iodine, and 0.7% in the control group (11 out of 1561 eyes).