Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Assessment of the risk of endophthalmitis in accidental globe penetration during strabismus surgery

Ali Akbar Saber Moghaddam & Abbas Kargozar

Assistant prof. of ophthalmology, Mashhad University of Medical Sciences, Iran

Tahereh Rashed

Prof of microbiology, Mashhad University of Medical Sciences, Iran

ABSTRACT:

Objective: To asses the risk of endophthalmitis if globe penetrated by suture needle during strabismus surgery.

Materials and Methods: Fornix & suture needle culture was performed in 28 eyes of 28 patients. Fornix sampling was performed before and after preparation of the eyes. Fornix samples and suture needle (at the end of operation) cultured in aerobic and anaerobic media. The findings analyzed by SPSS 10.1.

Results: Before preparation 25 cases (89.28%) was contaminated by staphylococcus (coagolase positive & negative), peptostreptococcus, gr positive bacillus , and Klebsiella. After preparation, 15 cases (60%) of infected samples change to sterile culture. Also 15 cases (60%) of needle culture were sterile (from 25 primary infected cases). Because close relation between the organisms cultured from pre-preparation samples and needle culture, so we conclude the most probable source of contamination is the normal flora of fornices. There was no evidence of cellulitis or significant conjunctivitis post operatively in our patients.

Conclusion: Because of high possibility of needle contamination by lid margin or fornix flora during strabismus surgery, care must be taken to avoid globe penetration and if it was happened, prophylaxis from endophthalmitis seems to be reasonable.

1INTRODUCTION

There are few reports of endophthalmitis following strabismus surgery. The estimated incidence ranges from 1:3500 to 1:1850001. Despite its major impact on visual outcome, the relative rarity of the event has made it difficult to study definitively. Both the source of the bacteria and the mode of transmission are unknown. Anecdotal reports have speculated on exogenous or endogenous sources, including normal or transient ocular flora2,3. Numerous studies have evaluated methods to decrease preoperative conjunctival bacterial counts in hope of decreasing the risk of infection after strabismus surgery4–6. Currently most pediatric ophthalmologists directly instill 5% povidone-iodine immediately before surgery, but no method completely sterilizes the conjunctiva in all cases7. Even if the host conjunctiva is a major source of infection, the mode of entry to the intraocular space remains unknown. Parks believes that a postoperative cellulitis or abscess precedes and initiates the endophthalmitis. Others suggest that scleral perforation from needles provides a method of access for bacteria2,3.

If scleral perforation is involved in the mechanism of endophthalmitis, then needle sterility is an important issue. If needles became contaminated from any source, including conjunctival flora, they could deposit bacteria intrasclerally in the suprachoroidal spaces or in the vitreous cavity.

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This study was undertaken to determine the sterility of needles that are used during strabismus surgery.

2METHODS

28 patients undergoing strabismus surgery by the author were eligible for enrollment. After sampling for aerobic and anaerobic cultures patients underwent a standard preoperative preparation in the operating room. No patient received preoperative prophylactic antibiotics. Sampling repeated immediately before operation (post preparation). At the conclusion of the surgery the needles used during the intrascleral pass to secure the muscle to the globe was collected for culture (directly in aerobic and anaerobic culture media). Any bacterial growth from either the aerobic or anaerobic media was considered positive. The results were analyzed by SPSS 10

3RESULTS

Before preparation 25 cases (89.28%) was contaminated by staphylococcus (coagolase positive & negative), peptostreptococcus, gr positive bacillus , and Klebsiella. After preparation, 15 cases (60%) of infected samples change to sterile culture. Also 15 cases (60%) of needle culture were sterile (from 25 primary infected cases). Because close relation between the organisms cultured from prepreparation samples and needle culture, so we conclude the most probable source of contamination is the normal flora of fornices. There was no evidence of cellulitis or significant conjunctivitis post operatively in our patients.

4DISCUSSION

Postoperative infection after strabismus surgery is a rare but potentially devastating event2 Estimates in the literature vary widely. Retrospective reviews have documented an incidence of between 1 in 3500 to 1 in 1850001 case. Ing documented an incidence of only 1 per 30000 cases8. Because of this low incidence, the cause and prevention of postoperative endophthalmitis is speculative.

Ing found no correlation between infection rate and the use of prophylactic antibiotics8. Most studies of the prevention of postoperative infection have concentrated on reducing the population of the patients own bacterial flora4–6. This philosophy assumes that patients own bacterial flora, either normal low virulent types or transient higher virulent types, is the source of postoperative infection. With use of molecular epidemiology, studies have demonstrated that the pathogens responsible for endophthalmitis after cataract surgery are identical to those residing on the patients own external tissue9,10. Farther more, 43% of patients undergoing uncomplicated cataract surgery demonstrate culture-positive anterior chamber aspirate 11. These studies strongly suggest that bacterial from external ocular structures are often introduced into the eye during cataract surgery and, if the bacterial load is large enough or virulence great enough, an infection may occur. It may be logical to extrapolate these results to strabismus surgery and postulate that the patients own bacterial flora is somehow introduced into the eye and that this may then increase the risk for development of an intraocular infection.

Globe perforation during strabismus surgery is not uncommon. It has been estimated to occur in between 1% and 12% of cases 12. Most perforations are not detected during surgery. The intraocular inoculation of exogenous bacterial could occur through the perforation site after surgery or at the time of the surgery if the needle was not sterile. The results of our study show that these needles are not always sterile. In 40% of our cases, the needle was found to be contaminated. As the results indicated, bacteria grown from these needles closely resemble culture results of normal conjunctival flora. Therefore it is logical to hypothesize that the needles used during strabismus surgery may be a method by which resident bacterial are introduced into the eye during surgery.

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However the introduction of bacteria into the suprachoroidal or deeper spaces of the eye does not equate with clinical infection. If scleral perforation occur at least 1% of the time and these needles are contaminated by conjunctival flora at the rate of about 40%, then bacteria could be introduced 0/40% of the time. This is a rate of 4 per 1000 cases, a number, although low, that is considerably higher than the rate of endophthalmitis. It is however close to the rate of overall periocular infection13.

This study was performed to evaluate the incidence of needle contamination during strabismus surgery.

5CONCLUSION

Because of high possibility of needle contamination by lid margin or fornix flora during strabismus surgery, care must be taken to avoid globe penetration and if it was happened, prophylaxis from endophthalmitis seems to be reasonable.

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