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Comparison of 5% povidone-iodine solution against 1% povidone-iodine solution in preoperative cataract surgery antisepsis: a prospective randomised double blind study
  1. A W Ferguson1,2,
  2. J A Scott1,
  3. J McGavigan3,
  4. R A Elton4,
  5. J McLean1,
  6. U Schmidt1,
  7. R Kelkar1,
  8. B Dhillon2
  1. 1Department of Ophthalmology, Stirling Royal Infirmary, Forth Valley Acute Hospitals NHS Trust, Livilands, Stirling, FK8 2AL, UK
  2. 2Princess Alexandra Eye Pavilion, Chalmers Street, Edinburgh EH3 9HA, UK
  3. 3Department of Microbiology, Stirling Royal Infirmary, Forth Valley Acute Hospitals NHS Trust, Livilands, Stirling, FK8 2AL, UK
  4. 4Rob Elton Consulting, Statistical Services for Medical Research, 5 Wilton Road, Edinburgh EH16 5NX, UK
  1. Correspondence to: Andrew Ferguson, Department of Ophthalmology, Ninewells Hospital, DundeeDD1 9SY, UK; aferguson{at}


Background/aim: Povidone-iodine (PI, Betadine) is routinely used as a preoperative topical antiseptic in cataract surgery as it has been shown to reduce the incidence of postoperative endophthalmitis. However, the concentration used clinically is variable. In vitro studies have shown that PI is paradoxically more effective at lower concentration. This study was undertaken to determine if this effect was reproducible in vivo.

Methods: A prospective randomised double blind study was carried out in the ophthalmic theatre in a district general hospital. 105 patients attending for routine cataract surgery were randomly allocated to have their conjunctival fornices irrigated preoperatively with either PI 1% (group A) or PI 5% (group B). Conjunctival swabs were taken, in identical fashion, both before and 1 minute after irrigation. The number and species of bacterial colonies cultured from each swab was counted. The difference in the median number of bacterial colonies from pre-irrigation to post-irrigation cultures was then compared between the groups.

Results: Bacterial cultures were gained from 100 patients (33 male, 67 female, mean age 74 years, range 30–95 years). Group B (5% PI) showed a decrease in median colony forming units (CFU) pre-irrigation from 100 to 40 CFU post-irrigation (a drop of 60%). This was greater than in group A (1% PI) where the reduction was 120 CFU pre-irrigation to 100 CFU post-irrigation (a drop of 16.7%) (Mann-Whitney test, p<0.05). At higher initial bacterial loads (CFU pre-irrigation >1000), the difference in median between the two groups became larger as the number of pre-irrigation bacteria increased. In group B pre-irrigation CFU reduced from 3340 to 110 post-irrigation (a drop of 96.7%) compared with group A: 5000 CFU pre-irrigation to 3000 post-irrigation (a drop of 40%) (Mann-Whitney test, p=0.0014).

Conclusion: Despite in vitro evidence of higher bactericidal efficacy of PI at more dilute concentrations, 5% PI is more effective than 1% PI in decreasing the human conjunctival bacterial flora in vivo, particularly in the presence of heavier initial bacterial load.

  • povidone-iodine
  • endophthalmitis
  • phacoemulsification
  • antiseptic

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  • Funding: This study was supported by a grant from the Forth Valley Acute Hospitals Research and Development fund.

  • Competing interest: None.

  • This study was presented at the annual meeting of the Scottish Ophthalmological Club on 8 March 2002.

  • The authors declare no competing or proprietary interest in Betadine or other products.

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